Neoadjuvant Pembrolizumab Research Articles

Abstract PO2-03-10: Association of pathologic complete response with the 27-gene IO score and week 3 IOpath response following neoadjuvant pembrolizumab +/- intralymphatic cytokines in the neoIRX trial

Abstract Introduction: Novel biomarker strategies are needed to identify immunotherapy (IO)-sensitive early-stage triple-negative breast cancers (TNBC). We recently reported a phase II trial (neoIRX, NCT04373031) evaluating induction IO (pembrolizumab +/- intralymphatic cytokines, IRX-2, comprised of physiologic doses of IL-2, IFNγ, and other cytokines derived from activated donor lymphocytes) preceding de-escalated neoadjuvant chemotherapy (NAC). Here, we report associations of response with the 27-gene IO score (DetermaIO), a commercially available RT-qPCR assay shown to predict IO response in the neoPACT, I-SPY2, and neoTRIP trials. We also propose a novel surrogate endpoint, entitled “IOpath” response, that characterizes radiographic and pathologic response following single-cycle IO and may be useful for guiding NAC de-escalation or omission. Methods: Subjects with stage II-III TNBC were randomized 1:1 (n=12) to receive induction pembrolizumab (200mg IV) +/- peri-areolar IRX-2 (IRX-2 arm: 1 ml SQ x2 daily for 10 days + cyclophosphamide 300 mg/m2 IV x 1) preceding initiation of pembrolizumab + NAC. The primary endpoint was pathologic complete response (pCR) rate. Post-induction IO response (IOpath) was assessed by week 3 ultrasound (US) and biopsy. IOpath response was designated as IOpath-NR (non-response: radiographic progression and/or biopsy non-response [neither treatment effect nor TILs expansion]), IOpath-PR (partial response: viable tumor with either treatment effect or TILs expansion), IOpath-CR (complete response: treatment effect with no viable tumor), or IOpath-NE (not evaluable). Results: The IRX-2 arm achieved 83% pCR (n=5/6, CI 36-100%) compared to 33% pCR with pembrolizumab alone (n=2/6, CI 4-78%) and was well tolerated (67% grade I skin bruise). Baseline 27-gene IO score predicted pCR (AUC 0.77, IO+: 5/6 pCR; IO-: 2/6 pCR) and week 3 IOpath response (AUC 0.85, IO+: 3/5 IOpath-CR/PR; IO-: 1/4 IOpath-PR), and outperformed TILs (AUC for pCR: 0.66; AUC for IOpath: 0.68) and CPS score (AUC for pCR: 0.63, AUC for IOpath: 0.58). Week 3 IOpath response was associated with 100% pCR (IOpath+: 4/4 pCR; IOpath-: 2/5 pCR). Conclusion: A subset of TNBCs experience brisk IO response following single-cycle IO (IOpath response), which is associated with 100% pCR in this preliminary dataset, highlighting IOpath as a potential surrogate biomarker to guide NAC de-escalation or omission in early-stage TNBC. Baseline 27-gene IO score predicts pCR and week 3 IOpath response. A future study is planned (neoINBRX) to evaluate the feasibility of combining baseline IO score with week 3 IOpath response to identify and treat IO-sensitive tumors with chemotherapy-sparing IO combination therapy. Acknowledgements: The study was funded in part by Merck, Sharpe, & Dohme as part of the Merck Investigator Studies Program, and by BrooklynImmunotherapeutics. Citation Format: David Page, Alan Su, Nicole Moxon, Staci Mellinger, Tracy Kelly, Nicole Fredrich, Amanda Seino, Zheng Topp, Philippa Newell, Kristen Massimino, Shaghayegh Aliabadi, Yaping Wu, Maritza Martel, William Redmond, Yoshinobu Kogushi, Grace Mcgee, Alejandra Mendez-Torres, Zhaoyu Sun, James Imatani, Alison Conlin, Kelly Perlewitz, Tyler Nielsen, Sasha Stanton. Association of pathologic complete response with the 27-gene IO score and week 3 IOpath response following neoadjuvant pembrolizumab +/- intralymphatic cytokines in the neoIRX trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-03-10.

Abstract PO3-03-11: Receptor discordance after neoadjuvant chemotherapy with pembrolizumab in early-stage triple-negative breast cancer

Abstract Background: Discordance in hormone receptor (HR) and/or HER2 status between matched primary tumors and residual specimens following neoadjuvant therapy is a known phenomenon. In the neoadjuvant setting, systemic treatment is primarily informed by the HR and HER2 status from the diagnostic biopsy. Current guidelines recommend additional adjuvant capecitabine and/or pembrolizumab and/or olaparib for patients with triple-negative breast cancer (TNBC) after neoadjuvant systemic therapy if residual disease is present at the time of surgery. Discordance in biomarker status between the initial diagnosis and residual cancer may impact postoperative systemic therapy recommendations. This study aims to investigate the discordance rate in HR and HER2 status after neoadjuvant chemotherapy (NAC) plus pembrolizumab in early-stage TNBC. Furthermore, given the emerging data in support of novel antibody-drug conjugates (ADCs) for HER2-low breast cancer, the prevalence of HER2-low disease following standard-of-care neoadjuvant therapy may have critical clinical importance. Methods: We performed a single-institution, retrospective study of early-stage TNBC patients diagnosed between February 1st, 2020 and December 1st, 2022 who were treated with neoadjuvant chemotherapy and pembrolizumab. Patients who had not undergone definitive surgery were excluded. Demographic information, clinical and pathologic characteristics, and treatment data were collected from an institutional database. Pathologic complete response (pCR) was defined as ypT0/Tis and ypN0. HR and HER2 status before and after neoadjuvant therapy were collected. This study was approved by an Institutional Review Board. Results: Among the 94 patients included the median age was 55 years (IQR 47.0-61.8). The majority of patients had invasive ductal carcinomas (90.4%), were clinical T2 stage (68.1%), and node negative (55.3%). On the core tumor biopsy, estrogen receptor (ER) was < 1% in 90 (95.7%) patients and 1-10% in 4 (4.3%) of patients. Progesterone receptor (PR) was < 1% in 91 (96.8%) of patients and 1-10% in 3 (3.2%) of patients. HER2 was 0 by IHC in 49 (52.1%) patients, 1+ in 30 (31.9%) patients, 2+ in 11 (11.7%) patients, and not performed in 4 (4.3%) patients. A pCR (ypT0/Tis ypN0) was achieved in 60 (63.8%) of the 94 patients. In the 34 patients with residual disease, 29 patients had ER status evaluated at the time of surgery. Of these patients, 4 had tumors with ER < 1% at baseline but >5% at surgery. 28 patients with residual disease had PR evaluated at the time of surgery. Of these patients, all had tumors with PR < 1% at the time of surgery. 28 patients had residual tumors with HER2 status evaluated at the time of surgery (table). Of these patients, 18 (64.3%) tumor specimens were HER2-ultra-low, 9 (32.1%) were HER2-low-positive, and 1 (3.6%) was HER2-positive. Conclusion: Receptor discordance from the time of initial biopsy to residual disease can occur in patients with early-stage TNBC treated with NAC with pembro. As additional systemic therapy is indicated in patients who do not achieve pCR, accurate tumor marker status is critical. This study highlights the potential impact of reassessment of HR and HER2 status on the surgical tumor specimen. Clinical trials that tailor adjuvant therapy recommendations based on residual biomarker analyses may further improve outcomes for women with high risk TNBC. Table. Discordance in HER2 Status Between Primary Tumor and Residual Specimen Citation Format: Alexis LeVee, Megan Wong, Sarah Flores, Nora Ruel, Heather McArthur, James Waisman, Joanne Mortimer. Receptor discordance after neoadjuvant chemotherapy with pembrolizumab in early-stage triple-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-03-11.

Abstract PO2-16-09: Dose-dense versus 3-weekly AC during Neoadjuvant Chemoimmunotherapy for Early-Stage Triple-Negative Breast Cancer (TNBC): a Real-World Safety and Efficacy Data Analysis

Abstract Background: The Keynote-522 (KN-522) study established the use of pembrolizumab in combination with neoadjuvant carboplatin-paclitaxel, followed by 3-weekly (3w) anthracycline-cyclophosphamide (AC), as the standard of treatment for stage II-III TNBC. However, dose-dense chemotherapy (CT) improves survival rates compared to the standard schedule in early-stage breast cancer and several groups have been modifying the KN-522 regimen with dose-dense AC (ddAC). The objective of this study was to compare the safety and effectiveness of ddAC versus the q3w schedule. Methods: We conducted a multicentric real-world analysis of patients (pts) with early-stage TNBC who received neoadjuvant CT plus pembrolizumab at nine cancer centers. Safety endpoints included grade ≥ 3 adverse events (AEs), drug discontinuation, hospitalization due to AEs, and the use of antibiotics during neoadjuvant therapy. Pathologic complete response (pCR) was used as the effectiveness endpoint, and we performed univariate and multivariable logistic regression to evaluate factors associated with pCR. Results: To date, we included 168 pts in this study of which 137 pts have finished the neoadjuvant therapy phase and constituted our safety cohort. Among them, 86 pts (62.8%) received ddAC and 51 pts (37.2%) were treated with the 3w schedule. The two groups exhibited no significant differences in baseline characteristics; the median age was 42 years (range 29 - 75), 70.8% had stage II and 25.5% had stage III TNBC, 46.7% had positive lymph nodes, and 74.4% had a Ki67-index ≥ 50%. Overalls, 30.2% and 27.4% presented grade ≥ 3 AEs with ddAC and 3w AC, respectively, with no significant difference between the two groups (p=0.177). Grade ≥ 3 immune-related AEs (irAEs), occurred in 8.1% with ddAC and 3.9% with 3w AC (0.335). The most common grade ≥ 3 irAEs were pneumonitis (n=4) and hepatitis (n=2). The ddAC group had a higher rate of any drug discontinuation due to toxicities (24.4% vs. 11.8%, p=0.043) and a greater use of antibiotics (27.9% vs. 11.8%, p=0.009) compared to the 3w group. There was a trend toward more rates of hospitalization due to AEs in the ddAC group, although this was not statistically significant (17.4% vs 11.8%, p=0.131). At the time of data analysis cutoff, a total of 119 pts underwent surgery and have pathology report available and were included in the efficacy cohort. In the univariate analysis, the pCR rates were 65.8% with ddAC and 55.8% with 3w AC (OR 1.52, 95% CI 0.70-3.27, p=0.282). The rates of RCB (residual cancer burden) 0-1 were 81.2% and 67.6%, respectively (OR 2.06, 95% CI 0.82 – 5.16, p=0.120). Factors influencing rates of pCR were Ki67 index ≥ 50% and tumor staging, which remained significant in the multivariable analysis (Table). In the 3w AC group, no difference in pCR was observed between pts who used or not granulocyte colony stimulating-factors (61.1% vs 52%, p=0.553). Conclusion: No difference in grade ≥ 3 AEs was observed between ddAC and 3w AC in pts with early-stage TNBC receiving neoadjuvant CT plus pembrolizumab. Nevertheless, the dose-dense regimen was linked to higher rates of drug discontinuation and antibiotic use. Although the pCR rates numerically favored ddAC, the difference was not statistically significant. Thus, the medical community should consider carefully risks and benefits of using ddAC within the KN522 regimen. Larger studies and longer follow-up are warranted to assess the long-term outcomes of the CT schedules. Multivariable regression of factors associated with pCR Citation Format: Renata Colombo Bonadio, Fernanda Madasi, José Bines, Rafael Ferreira, Daniela Rosa, Candice Santos, Zenaide Souza, Daniele Assad-Suzuki, Julio Araujo, Débora Gagliato, Carlos dos Anjos, Bruna Zucchetti, Anezka Ferrari, Mayana Lopes, Renata Cangussu, Maria Marcela Monteiro, Paulo Hoff, Laura Testa, Romualdo Barroso-Sousa. Dose-dense versus 3-weekly AC during Neoadjuvant Chemoimmunotherapy for Early-Stage Triple-Negative Breast Cancer (TNBC): a Real-World Safety and Efficacy Data Analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-09.

Abstract PO3-25-07: Characterization of tertiary lymphoid structures and its association with response to immune checkpoint inhibitors in triple negative breast cancer using spatial transcriptomics

Abstract Background Tertiary lymphoid structures (TLS) are ectopic lymphoid organs playing a role in adaptive antitumor immune response. They were shown to be associated with favorable outcome and appears to be a promising biomarker for response to immune checkpoint inhibitors (ICI). Yet, there is no consensus for their detection and quantification. Here we aimed to derive a specific TLS signature using high resolution spatial transcriptomics data from a large series of triple negative breast cancer (TNBC) samples and to assess its clinical relevance including response to ICI. Methods Spatial transcriptomics (ST) was performed on a series of 94 early-stage TNBC surgical samples with detailed clinicopathological and outcome data. TLS and tumor infiltrating lymphocytes (TILs) were scored using hematoxylin and eosin and double immunohistochemistry (CD3/CD20) stained slides by a dedicated breast pathologist. Regression based on morphological annotations and deconvolution methods estimated the fraction of gene expression related to TLS in each ST spot allowing to derive specific TLS signature. Its prognostic and predictive value of response to ICI was assessed using publicly available breast cancer (METABRIC, SCAN-B, and I-SPY2) and other tumor type datasets treated with ICI (Bareche et al. Ann Oncol, 2022) from bulk gene expression data. Results Deconvolution of the TLS compartments using the ST gene expression data showed that TLS are enriched in all B cell subsets, CD4+ (central) memory and naïve T cells, as well as mast cells. A functional analysis showed an enrichment of ‘vascular endothelial cell proliferation’, ‘mitotic G2/M transition checkpoint’, ‘V/D/J recombination’ and ‘regulation of cell chemotaxis to fibroblast growth factor’ suggesting that TLS aggregates are associated with angiogenesis, immune cell proliferation, adaptative humoral response and tissue remodeling. A comparison of gene expression data between TLS and non-aggregated TILs led to the development of a specific TLS gene signature comprising B and T cell-specific genes, immunoglobulin genes as well as genes associated with TLS initiation. Its projection on tumor slides overlapped with the regions annotated as TLS by the pathologist, demonstrating its specificity for TLS detection. As expected, the highest levels of the TLS signature were observed in the immunomodulatory TNBC molecular subtype and fully inflamed tumors, whereas the lowest levels were observed in the mesenchymal molecular subtype and immune desert tumors (p< 0.05). Of note, high levels of the TLS signature were associated with better prognosis in TNBC patients from METABRIC (p=6.5 10−5) and SCAN-B datasets (p=1.6 10−3) as well as with higher pathological complete response rates in all breast cancer patients treated with neoadjuvant pembrolizumab in the I-SPY2 study (p=0.026). Similar results were found in other tumor types treated with immunotherapy in the metastatic setting including metastatic melanoma, pancreatic and bladder cancers (PFS, p=6 10−6). Of interest, the TLS signature outperformed the predictive value of other immune-related signatures including TILs suggesting a key role of TLS in obtaining a sustainable, adaptive antitumor immune response in the vicinity of the tumor area. Conclusion By leveraging the potential of spatial transcriptomics, we have successfully developed a unique TLS gene signature that demonstrates a strong correlation with the response to ICI in breast cancer and various other tumor types. This TLS gene signature outperforms other immune biomarkers, underscoring the pivotal role of TLS in eliciting a robust antitumor immune response. The universality of this TLS signature makes it a potent biomarker capable of identifying patients who would benefit from immunotherapy, pending further validation. Citation Format: Xiaoxiao Wang, David Venet, Frédéric Lifrange, Denis Larsimont, Mattia Rediti, Linnea Stenbeck, Floriane Dupont, Ghizlane Rouas, Andrea Joaquin Garcia, David Gacquer, Ligia Craciun, Laurence Buisseret, Nayanika Bhalla, Yuvarani Masarapu, Kim Thrane, Eva Gracia Villacampa, Lovisa Franzén, Sami Saarenpää, Linda Kvastad, Joakim Lundeberg, Françoise Rothé, Christos Sotiriou. Characterization of tertiary lymphoid structures and its association with response to immune checkpoint inhibitors in triple negative breast cancer using spatial transcriptomics [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-25-07.

Abstract PS14-05: Safety evaluation from the KEYNOTE-522 study of neoadjuvant pembrolizumab (or placebo) plus chemotherapy followed by adjuvant pembrolizumab (or placebo) in patients with early triple-negative breast cancer (TNBC)

Abstract Background: In KEYNOTE-522 (NCT03036488), neoadjuvant (neoadj) pembrolizumab (pembro) + chemotherapy (chemo) followed by adjuvant (adj) pembro led to statistically significant and clinically meaningful improvements in the primary endpoints, pCR and EFS, vs neoadj placebo (pbo) + chemo followed by adj pbo in patients (pts) with newly diagnosed, high-risk, early TNBC. In the safety population at preplanned interim analysis 4 (IA4), treatment-related AEs in the combined phases (neoadj + adj) occurred in 98.9% of pts with pembro + chemo/pembro and 99.7% of pts with pbo + chemo/pbo; immune-mediated AEs of any grade occurred in 33.5% and 11.3% of pts, respectively. We report additional safety findings, beyond the already reported safety results, on immune-mediated AEs and management in the combined phases from IA4 of KEYNOTE-522. Methods: Eligible pts were randomized 2:1 to receive neoadj pembro 200 mg or pbo Q3W + paclitaxel-carboplatin for 4 cycles and then doxorubicin or epirubicin + cyclophosphamide for 4 cycles. After definitive surgery, pts received radiation therapy as indicated + adj pembro 200 mg or pbo Q3W for up to 9 cycles. Safety was assessed in all randomized pts who received ≥1 dose, underwent surgery, or both. AEs were monitored throughout the study and for 30 d post-treatment (90 d for serious AEs). Results: At IA4 (data cut-off: March 23, 2021), median treatment duration was 13.3 (range, 0-21.9) mo with pembro + chemo/pembro (n = 783) and 13.6 (range, 0-19.8) mo with pbo + chemo/pbo (n = 389). Of 341 pts with immune-mediated AEs and infusion reactions in the pembro + chemo/pembro arm (most events occurred in neoadj phase), 224 had grade 1-2 events and 117 had grade 3–5 events. The most common immune-mediated AEs with pembro + chemo/pembro were hypothyroidism (15.1%) and severe skin reactions (5.7%); infusion reactions occurred in 18.0% of pts (table). Of 118 pts with hypothyroidism, median time to onset was 105 d (range, 7–510 d) and 106 were treated with thyroid replacement, suggesting an endocrine abnormality and need for continued thyroid replacement. Of 45 pts with severe skin reactions, median time to onset was 64 d (range, 4–479 d) and 28 were treated with corticosteroids. Of 141 pts with infusion reactions, median time to onset was 16 d (range, 1–458 d) and 85 were treated with corticosteroids. Other immune-mediated AEs of interest with pembro + chemo/pembro were adrenal insufficiency (2.6%), pneumonitis (2.2%), and hypophysitis (1.9%); most of these events were grade 2–3. All 20 pts with adrenal insufficiency were treated with hormone replacement. Of 17 pts with pneumonitis, median time to onset was 167 d (range, 22-537 d) and 12 were treated with corticosteroids; median episode duration was 92 d. Of 15 pts with hypophysitis, 14 were treated with corticosteroids. Conclusion: In pts with newly diagnosed, high-risk, early TNBC, neoadj pembro + chemo followed by adj pembro had a manageable safety profile that was generally consistent with the known safety profiles of pembro and the chemo regimens. Most immune-mediated AEs and infusion reactions were grade 1-2, manageable with treatment interruption, corticosteroids, and/or hormone replacement therapy, and did not result in treatment discontinuation. Together with the efficacy findings, our results support neoadj pembro + chemo followed by adj pembro as a standard of care regimen for these pts. Table Citation Format: Javier Cortés, Rebecca Dent, Lajos Pusztai, Heather McArthur, Sherko Kuemmel, Carsten Denkert, Yeon Hee Park, Rina Hui, Masato Takahashi, Carlos Barrios, Yalin Zhu, Xiaoli Zhang, Wilbur Pan, Vassiliki Karantza, Joyce O'Shaughnessy, Peter Schmid. Safety evaluation from the KEYNOTE-522 study of neoadjuvant pembrolizumab (or placebo) plus chemotherapy followed by adjuvant pembrolizumab (or placebo) in patients with early triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS14-05.

Abstract GS01-02: Phase 3 study of neoadjuvant pembrolizumab or placebo plus chemotherapy, followed by adjuvant pembrolizumab or placebo plus endocrine therapy for early-stage high-risk ER+/HER2− breast cancer: KEYNOTE-756

Abstract Background: KEYNOTE-756 (NCT03725059) is a global phase 3 study of neoadjuvant pembrolizumab or placebo + chemotherapy followed by adjuvant pembrolizumab or placebo + endocrine therapy (ET) in patients with early-stage high-risk ER+/HER2– breast cancer. Here, we report primary pCR results and residual cancer burden (RCB) outcomes. Methods: Eligible patients with T1c-2 (≥2 cm) cN1-2 or T3-4 cN0-2, centrally confirmed, grade 3, invasive ductal ER+/HER2− breast cancer were randomized 1:1 to receive neoadjuvant pembrolizumab 200 mg Q3W or placebo, both given with paclitaxel QW for 12 weeks, then 4 cycles of doxorubicin or epirubicin + cyclophosphamide (neoadjuvant treatment). After definitive surgery (± radiation therapy), patients received pembrolizumab or placebo for 9 cycles + standard ET. Stratification factors include region (Eastern Europe, China, or Other), tumor PD-L1 status (CPS ≥1 [positive] vs CPS < 1 [negative]), nodal involvement (positive vs negative), ER positivity (≥10% vs < 10%) and anthracycline schedule (Q3W vs Q2W). Dual primary endpoints are pCR (ypT0/Tis ypN0) and EFS. Secondary endpoints include OS, pCR defined as ypT0 ypN0 and ypT0/Tis and safety. RCB was an exploratory endpoint and was assessed by a local pathologist at the time of surgery. RCB-0, -1, -2, and -3 denote increasingly larger residual disease. Results: 1278 patients were randomized to pembrolizumab + chemotherapy (n=635) or placebo + chemotherapy (n=643). At the final pCR analysis (May 25, 2023, first interim analysis data cutoff), median follow-up was 33.2 mo (range, 9.7-51.8). In the ITT population, pembrolizumab + chemotherapy showed a statistically significant improvement in pCR (ypT0/Tis ypN0) vs placebo + chemotherapy: 24.3% (95% CI, 21.0-27.8) vs 15.6% (95% CI, 12.8-18.6); estimated difference, 8.5 percentage points (95% CI, 4.2-12.8); P=0.00005; results were consistent for the secondary pCR definitions, ypT0 ypN0 (21.3% vs 12.8%) and ypT0/Tis (29.4% vs 18.2%). The benefit of pembrolizumab + chemotherapy on pCR was generally consistent in the prespecified subgroups. There were more patients with RCB-0 (24.7% vs. 15.6%) and RCB-1 (10.2% vs 8.1%) and fewer patients in the RCB-2 (40.8% vs. 45.3%) and RCB-3 categories (20.5% vs. 28.9%) in the pembrolizumab group versus the placebo group. In the neoadjuvant phase, grade ≥3 treatment-related AE rates were 52.5% with pembrolizumab + chemotherapy and 46.4% with placebo + chemotherapy, with 1 death in the pembrolizumab arm due to acute myocardial infarction. EFS results are still immature and continue to be evaluated. Conclusions: The addition of pembrolizumab to chemotherapy significantly increased the pCR rate and shifted RCB to lower residual disease categories in patients with early-stage high-risk ER+/HER2− breast cancer. Safety was consistent with the known profiles of each regimen. Citation Format: Fatima Cardoso, Joyce O'Shaughnessy, Heather McArthur, Peter Schmid, Javier Cortés, Nadia Harbeck, Melinda Telli, David Cescon, Peter A. Fasching, Zhimin Shao, Delphine Loirat, Yeon Hee Park, Manuel Gonzalez Fernandez, Gabor Rubovszky, Seock-Ah Im, Rina Hui, Toshimi Takano, Fabrice André, Hiroyuki Yasojima, Zhenzhen Liu, Yu Ding, Liyi Jia, Vassiliki Karantza, Konstantinos Tryfonidis, Aditya Bardia. Phase 3 study of neoadjuvant pembrolizumab or placebo plus chemotherapy, followed by adjuvant pembrolizumab or placebo plus endocrine therapy for early-stage high-risk ER+/HER2− breast cancer: KEYNOTE-756 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr GS01-02.

Abstract PO1-18-04: Neoadjuvant pembrolizumab + decitabine followed by standard neoadjuvant chemotherapy for locally advanced HER2- breast cancer (NCT02957968)

Abstract Background: Higher levels of stromal tumor-infiltrating lymphocytes (sTILs) in breast cancers are associated with increased likelihood of pathologic complete response (pCR) to chemotherapy and improved outcomes. DNA methyltransferase inhibitors (DNMTi) can augment immune responses to cancers by upregulating tumor antigen and MHC expression, decreasing numbers and activity of myeloid derived suppressor cells (MDSC), and increasing responsiveness of T lymphocytes. We have shown that the DNMTi decitabine augments the effectiveness of immunotherapy against murine triple negative breast cancer (TNBC) using murine 4T1 and E0771 mammary carcinoma models. Methods: In a single-arm phase 2 study, patients with HER2-negative breast cancer who were candidates for neoadjuvant chemotherapy (NCT) received decitabine (15 mg/m2 × 4 doses over 5 days) followed by 2 doses of pembrolizumab (pembro) (200 mg, 2 weeks apart) – collectively, window immunotherapy – prior to starting NCT. Two research biopsies were obtained: 1 prior to the window immunotherapy and 1 afterwards, prior to starting NCT. Biopsies were analyzed using established procedures to quantify sTILs and PD-L1 expression. Patients proceeded to NCT and tumor resection per standard of care and were followed up for immune-related adverse events (irAEs) and response. The primary endpoint was change in sTILs. Key secondary endpoints were occurrence of irAEs and pCR following neoadjuvant treatment. After the study was opened, reported results of a phase 3 trial (KEYNOTE 522) led to allowing patients with TNBC to receive additional pembro (200 mg q3w) concurrently with standard NCT and adjuvantly following resection (Cohort A2). Results: 46 patients (median age 54.5 yrs, range 28-72; 71.7% White, 28.3% Black; 100% female) were enrolled and treated on study. 21 patients had TNBC and did not receive neoadjuvant pembro concurrently with NCT nor adjuvant pembro (Cohort A), 7 patients had TNBC and did receive neoadjuvant and/or adjuvant pembro (Cohort A2), and 18 patients were ER+ or PR+ and received neither concurrent nor adjuvant pembro (Cohort B). Blood samples collected after decitabine administration before the first pembro dose showed a 59% decrease (P< 0.01) in monocytic MDSCs compared to baseline; decrease in granulocytic MDSCs was not statistically significant. 37 patients had paired biopsies adequate for sTIL evaluation with a mean change from 23.4% to 30.3% (absolute change 6.9%, P< 0.001). Cohorts A/A2 experienced an absolute sTIL increase of 7.4% (P< 0.01); Cohort B experienced absolute sTIL increase of 6.1% (P=0.01). PD-L1 expression in tumors (H-score using MoAb 22C3 clone) increased by 43% (P< 0.01) across all cohorts. 16 of the 39 patients (41.0%) who proceeded to resection achieved pCR (n=12 of 27 [44.4%] in Cohorts A/A2 and n=4 of 13 [30.8%] in Cohort B). The most frequently reported irAEs were adrenal insufficiency (n=5, 10.9%), maculopapular rash (n=3, 6.5%), and hypothyroidism (n=3, 6.5%). Conclusions: Treatment in the pre-neoadjuvant window with decitabine and pembro could potentially sensitize breast cancers to standard NCT by recruitment of TILs to the tumor tissue. The treatment was well -tolerated at the tested doses. Funding: financial support and drug (pembrolizumab) were provided by Merck Citation Format: Harry Bear, Xiaoyan Deng, Dipankar Bandyopadhyay, Michael Idowu, Maciej Kmieciak, Monique Williams, Giovanni Archer, Lindsey Gwaltney, Patrick Dillon, Daniel Flora, Daniel Stover, Andrew Poklepovic, Mary Hackney, Masey Ross, Hetal Vachhani, Raphael Louie, Kandace McGuire, Amelia Grover, Tasnim Rahman, Amber Hendrix. Neoadjuvant pembrolizumab + decitabine followed by standard neoadjuvant chemotherapy for locally advanced HER2- breast cancer (NCT02957968) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-18-04.

Abstract PO4-19-05: OptimICE-pCR: De-escalation of therapy in early-stage TNBC patients who achieve pCR after neoadjuvant chemotherapy with checkpoint inhibitor therapy (Alliance A012103)

Abstract Background: For patients with stage II-III triple-negative breast cancer (TNBC), standard of care systemic therapy consists of neoadjuvant pembrolizumab with chemotherapy, followed by 27 weeks of adjuvant pembrolizumab based on the results of the phase III KEYNOTE-522 trial. This trial demonstrated that pathologic complete response (pCR) rates and event-free survival (EFS) were significantly better among patients who received neoadjuvant followed by adjuvant pembrolizumab in addition to chemotherapy compared to chemotherapy alone. An exploratory analysis from this study demonstrated better EFS among patients who experienced a pathologic complete response (pCR) to neoadjuvant therapy compared to those with residual disease. Additionally, other studies, including GeparNuevo, which did not include adjuvant checkpoint inhibition, demonstrated EFS benefit from the addition of preoperative checkpoint inhibitor therapy to chemotherapy. It is therefore unclear if adjuvant pembrolizumab improves outcomes for patients with early-stage TNBC who achieve a pCR after neoadjuvant pembrolizumab plus chemotherapy. OptimICE-pCR trial utilizes response to preoperative therapy to tailor adjuvant therapy, and the goal is to determine whether patients who achieve pCR to pembrolizumab plus chemotherapy can achieve a similar recurrence-free survival (RFS) with observation compared to adjuvant pembrolizumab monotherapy Methods: OptimICE-pCR is an open-label, multicenter, randomized phase III trial that is enrolling patients with stage T1cN1-2 or T2-4N0-2 TNBC. To be eligible, patients must have experienced a pCR after the completion of neoadjuvant therapy containing a minimum of six cycles of chemotherapy in combination with pembrolizumab. Participants are randomized 1:1 to receive either 27 weeks of adjuvant pembrolizumab or to observation. Participants on the pembrolizumab arm receive pembrolizumab 200 mg IV on day 1 of each 21-day cycle for 9 cycles, or 400 mg IV on day 1 of each 42-day cycle for 4 cycles, followed by one dose of 200 mg IV every 21 days. The primary objective is to evaluate whether observation results in non-inferior RFS compared to adjuvant pembrolizumab. Non-inferiority is defined as an estimated 3-year RFS of 91% or higher in the observation arm compared to 94% in the pembrolizumab arm. The total sample size will be 1,295 patients, which will provide 80% power at one-sided significance level of 0.05 to detect this difference, which corresponds to a non-inferiority hazard ratio of 1.52. Key secondary endpoints include overall survival, locoregional recurrence, quality of life, financial toxicity, work productivity impairment, cost-effectiveness, and safety and tolerability. Key correlative objectives include detection of ctDNA at baseline and association with RFS and association of key biomarkers (TILs, PDL1, immune gene expression) from the primary tumor with RFS. The trial is currently open and enrolling patients. Support: U10CA180821, U10CA180882; U24 CA196171; U10CA180820 (ECOG-ACRIN); U10CA180863 (CCTG); https://acknowledgments.alliancefound.org. ClinicalTrials.gov Identifier: NCT05812807 Citation Format: Sara Tolaney, Karla Ballman, Charles M Perou, David Cescon, Margaret Gatti-Mays, Victoria Blinder, Shoshana Rosenberg, Elizabeth Mittendorf, Anna Weiss, Hope Rugo, Alice Ho, Dana Casey, Baljit Singh, Fabrice Smieliauskas, Yara Abdou, Vijay Damarla, Jane Meisel, Lisa Carey, Ann Partridge. OptimICE-pCR: De-escalation of therapy in early-stage TNBC patients who achieve pCR after neoadjuvant chemotherapy with checkpoint inhibitor therapy (Alliance A012103) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-19-05.

Abstract PO3-03-06: Real-world efficacy and safety of neoadjuvant pembrolizumab plus chemotherapy in Brazilian patients with early-stage triple-negative breast cancer

Abstract Background: Early-stage triple-negative breast cancer (TNBC) is associated with high risk of early recurrence and disease-specific mortality. Studies suggest a sustained clinical benefit in patients with TNBC who have a pathological complete response (PCR) after neoadjuvant chemotherapy (NACT). In TNBC, the combination of immunotherapy based on immune checkpoint inhibitors (anti-PD-1/PD-L1) combined with chemotherapy has been shown to be effective both in the advanced and early. In the early-stage setting, the addition of pembrolizumab to platinum-containing NACT significantly increased pathological complete response (pCR). Methods: We performed a retrospective observational cohort study of patients diagnosed with TNBC, stage II-III, who received NACT with chemotherapy based on paclitaxel and carboplatin (TC) followed by doxorubicin plus cyclophosphamide (AC) associated with pembrolizumab, treated from June 2022 to July 2023, at AC Camargo Cancer Center, São Paulo, Brazil. Objectives: To investigate the real-world pCR rate and safety profile of early-stage TNBC treated with neoadjuvant chemotherapy (weekly TC, ddAC/AC) associated with pembrolizumab and to describe the clinical-pathological characteristics of this population. Results: Eighty patients received neoadjuvant pembrolizumab plus chemotherapy. Around 50.6% of patients were premenopausal, with a median age of 47 years old at diagnosis. About 18% carried a germline mutation in the BRCA1 (50%) .Regarding the pathological characteristics of the tumor, 90.9% were invasive ductal carcinoma (IDC), 80% had histological grade (HG) III, and average Tumor Infiltrating Lymphocytes (TILs) was 18%. In 94.8% of cases, Ki67 was expressed in more 20% of tumor cells. The expression of HER2 was low in 14%, and 5% were ER-low. Regarding the clinical stage of the primary tumor, (64.9%)cT2, (18%) cT3, (10%) cT1c, and (2.5%) cT4. Regarding regional lymph node staging, 48%, 33.7%, 10.3%, and 6.4% were classified as cN0, cN1, cN2a, and cN, respectively. Clinical stage was IIA (42.8%), IIB (24.6%), IIIA (14.2%), IIIB ( 9%), and IIIC (5%). Regarding chemotherapy, 57.1% received dose dense AC, 54% percent had chemotherapy-related toxicity, 35.7% had neutropenic fever, 32.4% required hospitalization, and 31% used antibiotics. 31% received eight cycles of neoadjuvant pembrolizumab and 53.2% of patients completed all NACT, among these patients, 61% had complete .A cutoff date, about 61% of patients have undergone surgery, and 66.6% achieved a complete pathological response (ypT0ypN0). Patients that received eight cycles of neoadjuvant pembrolizumab had a higher chance of pathological complete response rate (61% vs. 45.2%) p=0.073. Immune-related toxicities (IRT) were observed in 16.8% patients, being the most common endocrinologic and cutaneous, being G3 or higher in 46%. About 15.5% used corticosteroids. Fifty percent had already started or completed adjuvant therapy, from which 66.6% received only adjuvant pembrolizumab, 28% had adjuvant pembrolizumab plus capecitabine, 1.2% received adjuvant capecitabine, and 1.2% had adjuvant olaparib. Eight percent of our patients have already completed nine cycles of adjuvant pembrolizumab, 12.7% did not receive adjuvant pembrolizumab due to prior toxicity. In our cohort, we observed greater intercurrences related to ddAC versus conventional AC 61.4% versus 52.4%, p=0.492, therefore, it did not impact whether or not the chemotherapy was completed. Conclusion: Our cohort is composed mostly of pre-menopausal with stage IIA tumors. Most patients received ddAC, Fifty-four percent had chemotherapy-related toxicity. We observed a high rate of pCR (61%) on our patients have already undergone surgery, 66.6% achieved a complete pathological response.Of those who received 8 cycles of neoadjuvant pembrolizumab had a higher chance of pathological complete response rate (61% vs. 45.2%) p=0.073 Citation Format: isadora sousa, Ana Carolina M. Comini, Italo BORGES, Flavia C. Balint, Livia alexandre Martins, Debora G. Sousa, Solange M. Sanches, Marcelle G. Cesca, Vladmir Cordeiro de Lima, Monique Tavares. Real-world efficacy and safety of neoadjuvant pembrolizumab plus chemotherapy in Brazilian patients with early-stage triple-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-03-06.

Abstract PO3-17-10: Real-World evidence for Pembrolizumab-based neoadjuvant chemotherapy in early-stage triple negative breast cancer: a single institution experience

Abstract Introduction The improved pathologic complete response (pCR) and event-free survival observed in Keynote-522 trial (NCT03036488) led to the adoption of (neo)adjuvant pembrolizumab (pembro)-based chemotherapy (CT) for high-risk early-stage triple-negative breast cancer (eTNBC) in various jurisdictions. However, Real-World Evidence (RWE) for (neo)adjuvant pembro in this setting would further support its ongoing funding and utilization. The aim of this study was to provide RWE for (neo)adjuvant pembro in eTNBC in the United Arab Emirates (UAE), where patients often present with more-advanced disease stages and poorer prognostic profiles compared with North America and Europe. Method This is a retrospective cohort study involving all patients treated with pembro-based neoadjuvant chemotherapy (NACT) for eTNBC at a major cancer center (Tawam Hospital) in the UAE between October 2021 and June 2023. Patient characteristics, clinicopathologic features, immune related adverse events (irAE) and disease outcomes were reported by descriptive statistics. An exploratory analysis was also conducted to examine the associations between pCR and HER-2 status (HER2 negative vs HER2 low) as well pCR and treatment interruption (< vs = > 2 weeks). ResultA total of 41 patients, with a median age of 44 years, were included in this study. All had an ECOG status of 0-1. The clinical and pathological characteristics are provided in Table 1. Pathogenic germline BRCA (gBRCA) mutations were detected in 8 (21%) of the 38 patients who underwent testing, including 6 with gBRCA1 and 2 with gBRCA2), with additional TP53 and SMARC4 detected in one patient each. Approximately 66% of the patients (n = 27) completed surgery post neoadjuvant pembro+CT, of whom 18 (67%) had breast conserving surgery and 9 (33%) had mastectomy. Of the patients who underwent surgery, 60% (n = 16/27) achieved pCR including 68% (13/19) of the IHC 0+ and 37.5% (3/8) of the HER2 1+ or 2+ ISH negative (p-value = 0.429, Chi Square test). Of the total population, 16 (40%) did not complete NACT; 1 lost to follow-up, 9 were still on ongoing therapy, 2 discontinued therapy due to toxicity, and 4 developed progressions including 1 locoregional relapse, and 3 metastatic diseases. Of the 32 patients who completed at least 3 months of pembro-NACT, 14 (34%) reported any grade irAE: skin toxicity (N = 3, 21%), hypothyroidism (N = 8, 57%), Hyperthyroidism (N = 1, 7%), Hepatitis (N = 4, 28.5%), adrenal insufficiency (N = 1, 7%), and pneumonitis (N = 1, 7%). With a median follow up of 4.5 months, pembro was postponed in 4 patients and permanently discontinued in 1 secondary to severe pneumonitis requiring ICU admission. All irARs were graded at I and II, except for 1 grade III dermatitis, and 1 grade III pneumonitis. Interruption of IO was required for irAE in 5 (36%) patients, and steroids were administered in 4 (29%). pCR was observed in 6 (40%) patients out of 15 who experienced treatment interruption due to IrAE or CT and 10 out of 13 (77%) in those who did not experience treatment interruption (p = 0.04895, Chi-square test). Conclusion The pCR rates for Pembro-based NACT in this RWE study, involving patients with an overall higher risk disease, appeared to be consistent with those observed in keynote-522. Interestingly, pCR rates did not seem to differ between HER2 negative and HER2 low groups. However, pCR rates appeared to be lower in patients who experienced treatment interruptions. Approximately half of the patients developed irAE but the majority of the adverse events were of lower grade and did not require treatment interruptions. Overall, the RWE observed in this study supports the ongoing funding and utilization of Pembro-based NACT in eTNBC. Updated data, including the pCR rate and toxicity, will be presented at the meeting once most of the patients have completed surgery. Table 1: Clinical and Pathological Characteristics of patients (Nf41) XX- XX Citation Format: Aydah Al-Awadhi, Mouza AlShebli, Lina Wahba, Tallal Younis. Real-World evidence for Pembrolizumab-based neoadjuvant chemotherapy in early-stage triple negative breast cancer: a single institution experience [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-17-10.

Abstract PO2-03-06: Pathological complete response with chemotherapy and immune checkpoint inhibition in triple negative inflammatory breast cancer (TN-IBC)

Abstract BACKGROUND: Patients with stage III inflammatory breast cancer (IBC) are treated with tri-modality therapy consisting of neoadjuvant systemic therapy followed by modified radical mastectomy and post-mastectomy radiation therapy. Triple negative IBC (TN-IBC) is the subtype of IBC associated with the worst survival outcomes. Pathological complete response (pCR) rates after neoadjuvant chemotherapy have been historically low, with reports ranging between 13% and 42%. It is unknown if the addition of immune checkpoint inhibition to chemotherapy leads to improved pCR rate in TN-IBC as these patients were underrepresented in the seminal studies that led to the approval of chemoimmunotherapy for high-risk early-stage triple negative breast cancer (TNBC). METHODS: We conducted a retrospective analysis of patients with stage III TN-IBC who underwent breast surgery after receiving neoadjuvant chemoimmunotherapy. Patients were seen at Dana-Farber Cancer Institute (DFCI) or MD Anderson Cancer Center (MDACC). The analysis population consisted of all patients that were seen at either institution no more than 30 days after starting immunotherapy. The primary objective was the estimation of the pCR rate. An additional cohort of patients with TN-IBC treated with neoadjuvant chemotherapy and pembrolizumab while participating in the multi-institutional PELICAN trial (NCT03515798) will be added to the analysis at the time of the meeting. RESULTS: Thirty-seven patients (16 DFCI, 21 MDACC) were identified as having stage III TN-IBC and having received neoadjuvant chemoimmunotherapy. Twenty-five patients met criteria for inclusion in the analysis population. Patients in the DFCI cohort initiated treatment with chemoimmunotherapy between May 2021 and June 2022, and in the MDACC cohort between June 2021 and October 2022. Most patients were White (N=20, 80%), premenopausal (N=15, 60%) and overweight/obese (N=19, 76%). All patients received pembrolizumab-based therapy (Table 1). Among the 25 patients in the analysis population, 10 (40%) (95% CI: 21% to 61%) achieved a pCR, 6 patients experienced RCB-II and 9 RCB-III. At the time of last follow up, 84% of patients were alive. The results will be updated at the time of the meeting to include an additional cohort of 17 patients from the PELICAN trial. CONCLUSIONS: The addition of immune checkpoint inhibition to neoadjuvant chemotherapy led to a higher pCR rate in TN-IBC than most historical estimates. However this is still lower than what has been reported in TNBC in general. The investigation of novel systemic therapies is warranted in TN-IBC. Table 1. Patient characteristics and treatment received (analysis population) Citation Format: Filipa Lynce, Samuel Niman, Anthony Gonçalves, Megumi Kai, Sean Ryan, Elizabeth Troll, Rachel Layman, Antonio Giordano, Azadeh Nasrazadani, Faina Nakhlis, Jennifer Bellon, Laura Warren, Caroline Block, Susan Schumer, Anthony Lucci, Savitri Krishnamurthy, Florence Lerebours, Florence Dalenc, Christelle Levy, Thierry Petit, Marianne Leheurteur, Thomas Bachelot, Olivier Trédan, Sylvain Ladoire, Leonor Lopez Almeida, Christophe Zemmour, Sara Tolaney, Vicente Valero, François BERTUCCI, Meredith Regan, Wendy Woodward. Pathological complete response with chemotherapy and immune checkpoint inhibition in triple negative inflammatory breast cancer (TN-IBC) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-03-06.

Abstract PO4-03-06: Body mass index and response to neoadjuvant chemo-immunotherapy among women with primary triple negative breast cancer

Abstract Background: Elevated body mass index (BMI) is associated with lower rates of pathologic complete response (pCR) after neoadjuvant chemotherapy in patients with breast cancer. The addition of PD-1 receptor inhibition with pembrolizumab to neoadjuvant chemotherapy is now considered the standard of care for patients with stage II or III triple negative breast cancer (TNBC) based on results from the KEYNOTE-522 (KN-522) trial. In other cancer types such as melanoma and lung cancer, patients with overweight/obesity have better survival outcomes following treatment with immunotherapy compared to patients with normal weight, despite a higher incidence of any-grade immune-related adverse events (irAEs). Whether BMI is associated with differential response and toxicity in patients with TNBC treated with neoadjuvant chemo-immunotherapy is unknown. Methods: Patients with stage II-III TNBC treated with neoadjuvant chemotherapy plus pembrolizumab per the KN-522 regimen from 8/2021 – 9/2022 at Memorial Sloan Kettering Cancer Center were included in this retrospective study. Patient characteristics, tumor characteristics, treatments, surgical pathology information, and irAEs were abstracted from medical records. pCR was defined as absence of invasive or in situ carcinoma in breast and axillary node tissue surgical specimens. BMI was categorized per standard definitions: underweight/normal weight < 25 kg/m2, overweight 25-29.9 kg/m2, and obese >=30 kg/m2. Wilcoxon rank sum tests, Pearson’s chi-squared tests, and Kendall rank correlation tests were used to test associations between variables. Results: 143 patients were included in this study. 57 patients (39.8%) were underweight/normal weight, 46 (32.2%) were overweight, and 40 (28.0%) were obese. Overall, 79/143 patients (55.2%) experienced a pCR. Among patients with a pCR, median BMI was 26.3 kg/m2 (interquartile range [IQR] 23.1-30.5 kg/m2); among patients without a pCR, median BMI was 26.1 kg/m2 (IQR 23.6-30.0 kg/m2; p >0.9). There was no significant association between BMI category and pCR (p=0.9). Overall, 63/143 (44%) of patients experienced an irAE; 42 (29.4%) required treatment for an irAE. There were no associations between BMI and the incidence (p=0.5) or frequency (p=0.7) of irAEs. Conclusions: In this TNBC cohort treated with neoadjuvant chemo-immunotherapy, BMI was not associated with rates of pCR or irAEs. These findings highlight the divergent impact of BMI on immunotherapy response across cancer types. Confirmatory studies in independent cohorts are needed. Citation Format: Sherry Shen, Sara Myers, Yuan Chen, Stephanie Downs-Canner, Nour Abuhadra, Tiffany Traina, Mark Robson, Neil Iyengar. Body mass index and response to neoadjuvant chemo-immunotherapy among women with primary triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-03-06.

Abstract PO5-20-08: A Case of Multifocal Ductal Breast Carcinoma with Extension into Lobules and Concurrent Primary Colon Adenocarcinoma

Abstract Background Multifocal (MF) multicentric breast cancer is a form of breast cancer that consists of disease independently developing at various locations due to a tumor clone spreading within the ductal complex. Multifocal breast cancer is associated with increased local recurrence. Our case highlights an example of multifocal breast cancer and addresses treatment challenges. Case presentation The patient is a 52-year-old African American female with a history of HCV cirrhosis, diabetes mellitus, and hypertension who presented with a palpable 4 cm right breast mass, without adenopathy, clinically Stage II, T2N0. Mammogram revealed a 2.5 cm right breast mass and three right level 1 axillary nodes with biopsy confirming invasive ductal carcinoma with extension into the lobules, ER positive (3%)/PR-/HER2-, Ki-67 95%. Neoadjuvant paclitaxel, carboplatin, and pembrolizumab was initiated but she incurred complications of decompensated liver cirrhosis after the second cycle and treatment was held. After 2 cycles her tumor was not palpable, and surgery was recommended, but due to COVID infection and concurrent decompensated liver failure surgery management was delayed. She underwent staged surgery with partial mastectomy without lymph node exploration. Histopathology showed DCIS grade 3 with extension into lobules and invasive ductal carcinoma with no lymphovascular invasion and all margins were negative, pathological stage ypT3NxM0. Immunohistochemistry demonstrated partial ER+ (50%)/PR-/HER2-, Ki-67 80%. She was given 4 cycles of adjuvant cyclophosphamide, adriamycin, pembrolizumab and continued on maintenance pembrolizumab. The patient was found with anemia out of proportion to chemotherapy and underwent colonoscopy that showed a colonic mass. Biopsy showed a primary moderately differentiated colonic adenocarcinoma. Her re-excision with new margins for partial mastectomy had negative margins, and 2 negative sentinel lymph nodes for ypN0. Genetic testing was negative. She continued on adjuvant immunotherapy with pembrolizumab for breast cancer. She is planned to start on adjuvant anastrozole. Patient has completed adjuvant radiation treatment and has no new complaints. She is pending curative intent completion colectomy for colon cancer. Discussion This case of MF breast cancer is significant, as one foci was ER negative, which responded to neoadjuvant chemoimmunotherapy and other ER positive that did not respond to treatment and was surgically excised. The pathology report from the surgical specimen revealed DCIS with extension into the lobules. Due to her tenuous clinical condition, she had staged surgeries for breast cancer, and now colon cancer. Genetic testing is negative. Currently, there is insufficient data to suggest which surgical approach is preferred in MF breast cancer. Based on the literature, breast conservation therapy (BCT) is a feasible option and is oncologically safe. Due to the patients’ medical condition and infections, it was felt a less invasive surgery could offer cure and minimize complications. Our patient underwent neoadjuvant chemoimmunotherapy, followed by partial mastectomy, adjuvant chemoimmunotherapy, second staged completion breast surgery, radiation therapy, and anti-estrogen therapy. MF breast cancer is associated with increased lymph node involvement. A 2022 meta-analysis found that multifocal and multicentric breast cancer has a slightly increased risk of death as compared to unifocal tumors. Lastly, our patient is African American, and multifocal tumors occur with a higher incidence in African Americans (43.4%) and Asian patients (37%) as compared to whites (28.9%). This case of breast cancer highlights treatment challenges in a case of multifocal multicentric breast cancer occurring concurrently with a secondary primary colonic cancer. Citation Format: Rabab Jafry, Hina Khan, Jessica Jones. A Case of Multifocal Ductal Breast Carcinoma with Extension into Lobules and Concurrent Primary Colon Adenocarcinoma [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-20-08.

Abstract PO3-14-04: Prognostic value of systemic inflammatory markers in neoadjuvant chemotherapy for breast triple negative cancer with pembrolizumab: development of a nomogram

Abstract Introduction: Systemic inflammatory markers derived from peripheral blood cells, such as the neutrophil-lymphocyte ratio (NLR), derived neutrophil-lymphocyte ratio (dNLR), platelet-lymphocyte ratio (PLR), and lymphocyte-monocyte ratio (LMR), have shown promise as prognostic markers for various cancer types. Inflammation plays a crucial role in cancer development, progression, metastasis, and resistance to treatment. However, only a few preoperative biomarkers have been identified as independent prognostic markers. Systemic inflammatory markers offer a reliable and easily accessible approach for prognosis evaluation. Materials and Methods: This study evaluated two groups of patients who received neoadjuvant chemotherapy for triple-negative breast cancer outside of clinical trials. The first group underwent neoadjuvant chemotherapy in 2021 with the EC X4 and weekly paclitaxel regimen, whereas the second group received neoadjuvant chemotherapy in 2022 following the KEYNOTE-522 study protocol with pembrolizumab. A total of 44 patients were included, with 23 patients in the pembrolizumab group. The NLR was defined as the absolute blood neutrophil count divided by the absolute lymphocyte count, and the derived neutrophil/lymphocyte ratio (dNLR) was defined as the absolute neutrophil count divided by the derived lymphocyte count (absolute leukocyte count —neutrophil count). The PLR was defined as the absolute platelet count divided by the absolute lymphocyte count. The LMR was defined as the absolute lymphocyte count divided by the absolute monocyte count. The association between systemic inflammatory markers (NLR, dNLR, PLR, and LMR) and pathological complete response (pCR) was analyzed using statistical tests. Inflammatory markers were evaluated at the time of diagnosis, at the time of chemotherapy regimen change, and two weeks before surgery. The χ2 test or Fisher’s exact test was used to analyze the correlation between the inflammatory indices and clinicopathologic parameters. Student’s t-test was used to compare different groups of continuous parametric data. Results: The pCR rates were 67% in the standard therapy group and 87% in the pembrolizumab group. There were no significant differences in other clinical characteristics between the two groups. The NLR, dNLR, PLR, and LMR at 6 months showed statistically significant differences compared to baseline levels. This difference was more evident in patients undergoing pembrolizumab therapy. ROC curves for the pembrolizumab group demonstrated an area under the curve (AUC) of 0.737, indicating a strong correlation between these systemic inflammatory markers and pCR. Based on these data, a nomogram was constructed to predict the likelihood of achieving pCR in patients undergoing neoadjuvant pembrolizumab therapy. Conclusion: This study highlights the potential of systemic inflammatory markers as prognostic indicators in patients with TNBC undergoing neoadjuvant chemotherapy. The significant differences observed in the pembrolizumab group and the high AUC of the ROC curves suggest the utility of these markers in predicting treatment response. The developed nomogram provides a practical tool for clinicians to estimate the probability of pCR based on NLR, dNLR, PLR, and LMR. Further research and validation are required to confirm the clinical utility of these markers in larger patient cohorts. Nomogram –insert figure image– ROC curve –insert figure image– Citation Format: Filippo Giovanardi, Giancarlo Bisagni, Elisa Gasparini, Alessandra Bologna, Roberto Di Cicilia, Gabriella Moretti, Claudia Degli Esposti, Carmine Pinto. Prognostic value of systemic inflammatory markers in neoadjuvant chemotherapy for breast triple negative cancer with pembrolizumab: development of a nomogram [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-14-04.

Abstract PO5-13-08: Impact of systemic inflammation markers in response to neoadjuvant pembrolizumab and chemotherapy in triple-negative breast cancer - a retrospective analysis

Abstract Background: Immune checkpoint inhibitors (ICIs) have revolutionized the treatment landscape for triple-negative breast cancer (TNBC). Systemic inflammation has been linked to cancer development and overall poor outcomes. Routine blood parameters have been investigated as potential inflammatory biomarkers in patients (pts) with various types of cancer, such as the derived NLR (neutrophils/(leucocytes-neutrophils) ratio (dNLR). A high dNLR has been associated with worse survival in several types of cancer. Specifically, it has been linked to lower pathologic complete response (pCR) rates after neoadjuvant chemotherapy (CTx). We investigated the association between systemic inflammation markers (dNLR, LIPI score and platelet-to-lymphocyte ratio [PLR]) and pCR in early TNBC pts treated with CTx + pembrolizumab (Pemb). Methods: Retrospective analysis of pts with early TNBC treated with Pemb + CTx from April 2022 to March 2023. dNLR was estimated from analytical values of peripheral blood collected before treatment (baseline). dNLR was calculated as the ratio of the absolute neutrophil number to the difference between absolute total leukocyte and absolute neutrophil counts. Univariate and multivariate logistic regression analyses were used to explore the association of dNLR with main clinical characteristics and dNLR capability (distributed as a continuous variable, using median cut-off) to predict pCR. Results: The study included 86 TNBC pts with a median age of 51 years (IQR: 42.2 – 56-7). Most pts had stage II disease (64%) and presented grade 3 tumours (n=66; 78.5%). HER2 low tumours represented 27% (n=23) of the cohort. Germline mutations were present in 20 pts (23%) with the following distribution: BRCA1 (n=14), BRCA 2 (n=5) and PALB2 (n=1). The median stromal tumor infiltrating lymphocytes (TILs) was 20% (IQR: 10-30%). The median Ki67 was 70% (IQR:50%-80%). All pts received Pemb. The majority of pts received carboplatin plus paclitaxel, followed by EC90 (n=77 (90%), while 10% (n=9) did not receive anthracyclines. Data concerning surgical outcomes was available in 80 pts. Pathological complete response rate was 61.2% (n=49). Pts achieving pCR presented significantly higher TILs (p< 0.01). Residual cancer burden (RCB) class (n=80) was distributed as follows: 0: 61% (n=49); I: 13% (n=10); II: 20% (n=16); III: 1% (n=1) and non-assigned: 5% (n=4). In pts with germline mutations (n=20), the pCR rate was 85% (n=17). Median dNLR at baseline was 1.30 (interquartile range (IQR): 0.99 – 1.86). High baseline dNLR levels considered a continuous variable was associated with a higher likelihood of achieving a pCR in univariate (OR: 2.59; 95% CI: 1.01–6.6; p-value = 0.046) but not in multivariate (OR: 2.33; 95%; CI: 0.85–6.33; p-value = 0.097) logistic regression analysis (adjusted for stage and histologic grade). High baseline dNLR, defined by the median cut-off, was associated with an increased likelihood of achieving pCR in both univariate (OR: 3.85; 95% CI: 1.47–10.1; p-value = 0.006) and multivariate (OR: 3.72; 95% CI: 1.28–10.8; p-value = 0.016) logistic regression analysis (adjusted for stage and histologic grade). Conclusion: In this real-life cohort of early TNBC pts treated with Pemb and CTx we found similar pCR rates (61.2%) to the ones reported in the KN522 trial. No association between PLR or LIPI score with pCR was evidenced. High baseline dNLR (assessed as a continuous variable or by the median cut-off) was associated with a higher likelihood of pCR in the univariate analysis. In the multivariate analysis, only high baseline dNLR defined by the median cut-off retained an association with pCR after stage and histologic grade adjustment. Despite several limitations, these exploratory data provide initial evidence of a potential association between dNLR values and independent prediction of pCR. Further research to assess the role of dNLR as a predictive marker for pCR in early TNBC pts treated with CTx + immunotherapy is needed. Citation Format: Martina Spotti, Elie Rassy, Alessandro Viansone, Fiona Pham, Layal Rached, Barbara Pistilli, Charles-Antoine Dutertre, Joana Mourato Ribeiro. Impact of systemic inflammation markers in response to neoadjuvant pembrolizumab and chemotherapy in triple-negative breast cancer - a retrospective analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-13-08.

Abstract PO1-03-10: Differential microbial metabolic pathways associated with resistance to neoadjuvant immunotherapy in locally advanced triple negative breast cancer

Abstract Differential microbial metabolic pathways associated with resistance to neoadjuvant immunotherapy in locally advanced triple negative breast cancer Background: It has previously been shown that microbial metabolic pathways are differentially activated in immunotherapy resistance, hence can serve as potential targets for therapeutic intervention. With the advent of Immune Checkpoint Blockers in the neoadjuvant setting of locally advanced (LA) TNBC, we hypothesized that similar microbial metabolite mediated resistance may be at play. We are presenting the real world data for neoadjuvant treatment in early TNBC along with a subset of tumor metabolite analysis. Method: 35 patients who received neoadjuvant pembrolizumab and chemotherapy for LA TNBC were identified at Moffitt Cancer Center between July 2019 to January 2023. These included 22 Caucasian, 5 African American, 2 Hispanic and 6 patients with undisclosed race. The age range was 33-78 years. The weight and Body Mass Index range was 55.3 kg-127.3 kg and 20.96-45.43 kg/m2 respectively. Nine patients had stage III disease while 24 had stage II breast cancer. The response was assessed in 33 patients; 20 patients (60.6%) achieved pathological complete response (pCR) and 13 (39.4%) had residual disease (RD). 1 patient developed severe immune mediated toxicity with colitis, hepatitis, myasthenia gravis leading to death while 1 patient had disease progression leading to drug discontinuation. Six patients developed immune mediated adverse events. We conducted untargeted metabolomic profiling on 24 patients to identify differentially abundant metabolites associated with pCR (ypT0/is ypN0) vs RD; 16 vs 8 patients respectively. Formalin fixed paraffin embedded (FFPE) slides from tumor tissue vs tumor bed were retrieved and histopathological evaluation of tumor cells was performed. 20 μm sections of FFPE block were used for untargeted metabolomics via liquid chromatography/mass spectrometry. Among the 200 metabolites detected, 63 were differentially abundant between pCR and tumor samples with RD. After correcting for false discovery rate, we observed striking differential activation of two microbial metabolic pathways. Samples with RD had significantly elevated kynurenine (OR-3.64 X1034, P-1.94 X 10-74 and kynurenine/Tryptophan ratio). The tryptophan, kynurenine pathway has been known to be overexpressed in patients resistant to immunotherapy and modulated by the microbiome. Similarly, the purine metabolic pathway, specifically microbiota-derived immunostimulatory metabolites- inosine, hypoxanthine, uric acid were significantly depleted in patients with RD (Inosine OR-0.54, p-0.007, Hypoxanthine OR-0.5, p-0.00039, uric acid OR: 0.41, P-0.003). Previously Inosine has been shown to increase the anti-tumor effects of immune checkpoint blockade by enhancing CD8+ effector T-cell function. Hence depletion of inosine, hypoxanthine and uric acid signals lack of an effector CD8 T cell response. Conclusion: Despite being a small study, it corroborates pCR rates noted in KEYNOTE 522 in the real world setting but shows significant concern for serious immune mediated adverse effects. This highlights the importance of stratifying patients who might be resistant to ICB or develop significant toxicities, thus deriving little to no benefit from standard neoadjuvant treatment. This underscores the need to develop precision-based treatment algorithms. The study represents one of the first investigations of differential abundance of microbial metabolites with immunotherapy resistance in LA TNBC. Our results highlight two microbially mediated mechanisms that could be targeted to improve pCR rates in LA TNBC. We are working to identify microbial metabolic pathways associated with immune mediated toxicity. Citation Format: Humaira Sarfraz, Brian Czerniecki, Zena Jameel, Michael Jaglal, Mostafa Eysha, Turkan Ozkul, Jameel Muzaffar, Aditi Saha, Sara Sarfraz, Fatima Zahra, Min Liu, Khushali Jhaveri, Melissa Sur, Adrianna Bagos-Estevez, Shahla Bari. Differential microbial metabolic pathways associated with resistance to neoadjuvant immunotherapy in locally advanced triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-03-10.

Abstract PO2-22-10: Surgical outcomes after neoadjuvant chemotherapy with and without immunotherapy in patients with triple negative breast cancer

Abstract Background: The KEYNOTE-522 trial demonstrated that the addition of neoadjuvant pembrolizumab to neoadjuvant chemotherapy (NAC) for the treatment of early-stage triple negative breast cancer (TNBC) significantly improves rates of both pathologic complete response (pCR) and event-free survival. The impact of adding immunotherapy to NAC on surgical outcomes, however, is unknown. The purpose of this study is to compare 90-day surgical complication rates and timing to subsequent adjuvant therapy of patients undergoing neoadjuvant chemotherapy for stage I-III TNBC with and without immunotherapy. Methods: Patients treated at University of California, Los Angeles with neoadjuvant therapy for TNBC between 2018-2022 were identified retrospectively. Patient comorbidities, tumor characteristics, type of surgery, 90-day postoperative minor and major complications, timing to adjuvant therapy, and oncologic outcomes were reviewed and analyzed. Major complications were defined as those requiring reoperation or hospitalization. Results: A total of 44 patients were included, 15 patients received neoadjuvant chemotherapy with immunotherapy (NAC-I) and 29 patients received neoadjuvant chemotherapy alone (NAC). There was no difference in patient comorbidities between the groups. Compared to the NAC group, significantly more patients in the NAC-I group had stage II or III tumors (58.6% vs. 86.7%, respectively, p=0.028). 73% of patients in the NAC-I group underwent mastectomy compared to only 44% of patients in the NAC group (p=0.111). In total, 23 patients underwent reconstruction with mastectomy, 6 patients underwent immediate DIEP flap (4 in NAC-I group and 2 in NAC group) and 17 underwent immediate tissue expander (7 in NAC-I and 10 in NAC group). 80% of patients in the NAC-I experienced a pCR compared to only 44% in the NAC group (p=0.026). A total of 15 patients (34.1%) experienced surgical complications and there was no significant difference in the complication rate between the groups (p= 0.552). Five patients (33%) in the NAC-I group experienced minor complications of seroma requiring aspiration (n=4), cellulitis requiring antibiotics (n=1), or wound dehiscence requiring local wound care (n=2). No patients in the NAC-I group had major complications. Ten patients (33%) in the NAC group experienced complications, including 6 minor complications and 4 major complications including postoperative bleeding or flap necrosis requiring unplanned return to surgery or hyperbaric oxygen treatment. On multivariable regression analysis, controlling for patient characteristics, tumor stage, and preoperative immunotherapy, only younger age was a statistically significant variable associated with increased risk of surgical complications (p=0.012). Median time to adjuvant therapy, including radiation and/or systemic therapy, was similar between NAC-I and NAC groups, at 32 and 36 days, respectively (p=0.37). In the NAC-I group, 14 patients (93.3%) had adjuvant systemic therapy including pembrolizumab alone (n=12), pembrolizumab with olaparib (n=1) or capecitabine alone (n=1). In the NAC group, 11 patients (37.9%) underwent adjuvant systemic treatment including chemotherapy with either capecitabine (n=1), pembrolizumab (n=1), or olaparib (n=2); or single agent capecitabine (n=6) or olaparib (n=1). Conclusions: Despite patients in the NAC-I group having more advanced stage tumors and undergoing more extensive surgery and reconstruction compared to those in the NAC alone group, a significantly higher rate of surgical complications was not observed in the NAC-I group and there was no significant difference in time to adjuvant therapy between the two groups. Similar to results from the KEYNOTE-522 trial, more patients in the NAC-I group experienced a pCR compared to NAC alone. Larger studies are needed to continue to assess and optimize the surgical safety of neoadjuvant immunotherapy with chemotherapy in patients with TNBC. Citation Format: Anouchka Coste Holt, Maurice Berkowitz, Nicholas McAndrew, Courtney Smith, Jennifer Baker, Nimmi Kapoor. Surgical outcomes after neoadjuvant chemotherapy with and without immunotherapy in patients with triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-22-10.

Impact of neoadjuvant pembrolizumab adherence on pathologic complete response in triple-negative breast cancer: a real-world analysis.

The addition of pembrolizumab (pembro) to neoadjuvant chemotherapy (NAC) is standard of care for the treatment of early triple-negative breast cancer (TNBC) after KEYNOTE-522 trial demonstrated improved pathologic complete response (pCR) rates with the combination. However, the optimal treatment strategy for TNBC remains uncertain as questions persist about which patients benefit from pembro and the best treatment schedule and regimen. We identified real-world clinical characteristics and treatment variables associated with response to NAC plus pembro. Patients with early TNBC treated with NAC plus pembro between February 2020 and September 2023 were identified. Univariate and multivariate analysis was performed using logistic regression to identify factors associated with pCR. Cox proportional hazard prediction models were used to identify predictors of invasive disease-free survival and overall survival in this cohort. A pCR was achieved in 75 (63.6%) of 118 patients. Age at diagnosis (P = .04), Ki-67 (P = .004), duration from start of pembro to surgery (P = .006) and NAC to surgery (P = .01), number of cycles of pembro (P = .04) and NAC (P = .02), and completion of at least 8 cycles of pembro (P = .015) and NAC (P = .015) were each significantly associated with pCR in univariate analysis. In multivariate analysis, patients younger than 55 years at time of diagnosis (vs age > 55 years) and those completing at least 8 cycles of pembro remained predictive of pCR (OR's 2.50, 2.49, P = .035 and .037, respectively). In this real-world analysis of patients with TNBC treated with NAC plus pembro, younger age and the completion of at least 8 cycles of pembrolizumab were associated with pCR.

Elucidation of Spatial Cooperativity in Chemo-Immunotherapy by a Sequential Dual-pH-Responsive Drug Delivery System.

Combining immune checkpoint blockade with chemotherapy through nanotechnology is promising in terms of safety and efficacy. However, the distinct subcellular distribution of each ingredient's action site makes it challenging to acquire an optimal synergism. Herein, a dual-pH responsive hybrid polymeric micelle system, HNP(αPDL16.9, Dox5.3), is constructed as a proof-of-concept for the spatial cooperativity in chemo-immunotherapy. HNP retains the inherent pH-transition of each polymer, with stepwise disassembly under discrete pH thresholds. Within weakly acidic extracellular tumor environment, αPDL1 is first released to block the checkpoint on cell membranes. The remaining intact Doxorubicin-loaded micelle NP(Dox)5.3 displays significant tropism toward tumor cells and releases Dox upon lysosomal pH for efficient tumor immunogenic cell death without immune toxicity. This sequential-released pattern boosts DC activation and primes CD8+ T cells, leading to enhanced therapeutic performance than single agent or an inverse-ordered combination in multiple murine tumor models. Using HNP, the indispensable role of conventional type 1 DC (cDC1) is identified in chemo-immunotherapy. A co-signature of cDC1 and CD8 correlates with cancer patient survival after neoadjuvant Pembrolizumab plus chemotherapy in clinic. This study highlights spatial cooperativity of chemo- and immuno-agents in immunoregulation and provides insights into the rational design of drug combination for future nanotherapeutics development.

Neoadjuvant followed by adjuvant pembrolizumab in melanoma: time biases in the data analysis of the SWOG S1801 trial.

The SWOG S1801 trial investigated the role of pembrolizumab, an anti-PD1 immune checkpoint inhibitor, in the perioperative setting of stage III or IV melanoma. This phase 2 trial compared two groups: one receiving pembrolizumab both before and after surgery (neoadjuvant-adjuvant), and another receiving it only post-surgery (adjuvant-only), with event-free survival (EFS) as the primary endpoint. Neoadjuvant strategies, involving pre-surgical drug administration, potentially offer rapid tumor control and a unique opportunity to assess tumor response. However, they may expose to toxicity and delay or preclude surgery. The study met its primary endpoint, with a 72 % EFS rate in the neoadjuvant-adjuvant group, and 49 % in the adjuvant group. Here, we question the results' applicability with three potential limitations. Key concerns include an arbitrary rule in event assignment, possibly affecting the event distribution over time. Second, different rates of early censoring between groups introduce the possibility of informative censoring, which could have led to an artefactual benefit in EFS. Lastly, phase 2 trial results, by definition, carry risk of fluke results, and should be confirmed in phase 3 trial before wide adoption. Collectively, these factors must be integrated into a careful interpretation of the SWOG S1801 trial outcomes. More robust data are needed to fully appraise strengths and limitations of neoadjuvant pembrolizumab in melanoma treatment.