Early-stage Triple-negative Breast Cancer Research Articles

Assessment of efficacy and safety of dose-dense doxorubicin and cyclophosphamide (ddAC) in combination with immunotherapy in early-stage triple-negative breast cancer.

This study aimed to assess safety and efficacy of a modified KEYNOTE 522 protocol, which incorporated pembrolizumab every 6weeks, allowing for concomitant dose-dense (14day) doxorubicin and cyclophosphamide (ddAC). By optimizing this dosing, the intention of this modified protocol was to improve pathologic complete response (pCR) rates in a population associated with a poorer prognosis. This was a retrospective, single-center, cohort study. Patients were included if they had early stage, triple-negative breast cancer, and received at least one dose of AC. The entire cohort received neoadjuvant chemotherapy including weekly carboplatin and paclitaxel with pembrolizumab every 3weeks for 12weeks (4 cycles). The group then received either ddAC with pembrolizumab 400mg every 6weeks, or AC with pembrolizumab 200mg every 3weeks. The primary objective was pCR rate at time of surgery. This study assessed outcomes in 25 patients over 34months. The pCR rate in the pembrolizumab, AC 3-week cohort was 64.3% versus 81.8% in the ddAC and 6-week pembrolizumab group. No pembrolizumab-associated grade 3-4 adverse events occurred in the either cohort. Despite seeing an increased incidence of grade 3-4 toxicities in the ddAC arm, this did not result in additional chemotherapy delays or dose reductions. This study demonstrated tolerability and a potential for favorable outcomes with this patient population, making this modified KEYNOTE 522 protocol a reasonable treatment approach. Larger, prospective studies are warranted to assess the feasibility of this dosing and true optimization of patient outcomes given the small sample size of this study.

Stability and variability of molecular subtypes: comparative analysis of primary and metastatic triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive cancer. Although our previous study classified primary TNBC into four subtypes, comprehensive longitudinal investigations are lacking. We assembled a large-scale, real-world cohort comprised of 880 TNBC patients [465 early-stage TNBC (eTNBC) and 415 metastatic TNBC (mTNBC) patients] who were treated at Fudan University Shanghai Cancer Center. The longitudinal dynamics of TNBC subtypes during disease progression were elucidated in this patient cohort. Comprehensive analysis was performed to compare primary and metastatic lesions within specific TNBC subtypes. The recurrence and metastasis rates within 3 years after initial diagnosis in the eTNBC cohort were 10.1% (47/465). The median overall survival (OS) in the mTNBC cohort was 27.2 months [95% confidence interval (CI), 24.4-30.2 months], which indicated a poor prognosis. The prognostic significance of the original molecular subtypes in both eTNBC and mTNBC patients was confirmed. Consistent molecular subtypes were maintained in 77.5% of the patients throughout disease progression with the mesenchymal-like (MES) subtype demonstrating a tendency for subtype transition and brain metastasis. Additionally, a precision treatment strategy based on the metastatic MES subtype of target lesions resulted in improved progression-free survival in the FUTURE trial. Our longitudinal study comprehensively revealed the clinical characteristics and survival of patients with the original TNBC subtypes and validated the consistency of most molecular subtypes throughout disease progression. However, we emphasize the major importance of repeat pathologic confirmation of the MES subtype.

A 10-Gene Signature to Predict the Prognosis of Early-Stage Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a particularly challenging subtype of breast cancer, with a poorer prognosis compared to other subtypes. Unfortunately, unlike luminal type cancers, there is no validated biomarker to predict the prognosis of patients with early-stage TNBC. Accurate biomarkers are needed to establish effective therapeutic strategies. In this study, we analyzed gene expression profiles of tumor samples from 184 TNBC patients (training cohort, n=76; validation cohort, n=108) using RNA sequencing. By combining weighted gene expression, we identified a 10-gene signature (DGKH, GADD45B, KLF7, LYST, NR6A1, PYCARD, ROBO1, SLC22A20P, SLC24A3, and SLC45A4) that stratified patients by risk score with high sensitivity (92.31%), specificity (92.06%), and accuracy (92.11%) for invasive disease-free survival. The 10-gene signature was validated in a separate institution cohort and supported by meta-analysis for biological relevance to well-known driving pathways in TNBC. Furthermore, the 10-gene signature was the only independent factor for invasive disease-free survival in multivariate analysis when compared to other potential biomarkers of TNBC molecular subtypes and T-cell receptor β diversity. 10-gene signature also further categorized patients classified as molecular subtypes according to risk scores. Our novel findings may help address the prognostic challenges in TNBC and the 10-gene signature could serve as a novel biomarker for risk-based patient care.

Screening optimal candidates with operable, early-stage triple-negative breast cancer benefitting from capecitabine maintenance: A post-hoc analysis of the SYSUCC-001 study

BackgroundTo explore whether specific clinicopathological covariates are predictive for a benefit from capecitabine maintenance in early-stage triple-negative breast cancer (TNBC) in the SYSUCC-001 phase III clinical trial. MethodsCandidate covariates included age, menstrual status, type of surgery, postoperative chemotherapy regimen, Ki-67 percentage, histologic grade, primary tumor size, lymphovascular invasion, node status, and capecitabine medication. Their nonlinear effects were modeled by restricted cubic spline. The primary endpoint was disease-free survival (DFS). A survival prediction model was constructed using Cox proportional hazards regression analysis. ResultsAll 434 participants (306 in development cohort and 128 in validation cohort) were analyzed. The estimated 5-year DFS in development and validation cohorts were 77.8 % (95 % CI, 72.9%–82.7 %) and 78.2 % (95 % CI, 70.9%–85.5 %), respectively. Age and node status had significant nonlinear effects on DFS. The prediction model constructed using four covariates (node status, lymphovascular invasion, capecitabine maintenance, and age) demonstrated satisfactory calibration and fair discrimination ability, with C-index of 0.722 (95 % CI, 0.662–0.781) and 0.764 (95 % CI, 0.668–0.859) in development and validation cohorts, respectively. Moreover, patient classification was conducted according to their risk scores calculated using our model, in which, notable survival benefits were reported in low-risk subpopulations. An easy-to-use online calculator for predicting benefit of capecitabine maintenance was also designed. ConclusionsThe evidence-based prediction model can be readily assessed at baseline, which might help decision making in clinical practice and optimize patient stratification, especially for those with low-risk, capecitabine maintenance might be a potential strategy in the early-disease setting.

Abstract PO3-03-07: Patterns of Chemotherapy Utilization among Elderly Patients with Early-Stage Triple-Negative Breast Cancer

Abstract Background: Patterns of adjuvant and neoadjuvant chemotherapy use among patients with breast cancer have changed over time. Historically, adjuvant chemotherapy has been the standard treatment approach for patients with triple-negative breast cancer after surgical resection, aiming to eliminate any remaining cancer cells and reduce the risk of recurrence. Advancements in treatment strategies, research findings, and clinical guidelines have contributed to shifts in cancer care approaches, with an increase in the use of neoadjuvant chemotherapy. In this study, we explore chemotherapy utilization in a large cohort of elderly patients diagnosed with early-stage triple-negative breast cancer (TNBC). Methods: Data were obtained from the SEER- and Texas Cancer Registry (TCR)-linked Medicare databases. We identified female patients aged 66 years or older, diagnosed with early-stage (localized or regional disease) TNBC between 2010 and 2017 with claims until 2019. We identified the use of chemotherapy using HCPCS codes from outpatient and physician’s carrier claims. We used descriptive statistics and analyzed overall chemotherapy utilization and time trends of neoadjuvant versus adjuvant use via the Cochran-Armitage trend test, and evaluated factors associated with chemotherapy use via logistic regression models. This study adhered to the STROBE reporting guidelines for cohort studies. Results: Among 8,848 patients with localized or regional stage TNBC (median age 74) a total of 5,159 (58%) were treated with chemotherapy. The rate of chemotherapy utilization increased yearly from 52% in 2010 to 66% in 2017 (p< 0.001). After multivariable adjustment, any chemotherapy use was associated with recent year of diagnosis (OR=1.77; 95%CI 1.54-2.04), regional stage compared to localized (OR=3.78; 95%CI 3.34-4.27), and Northeastern region compared to South (OR=1.2; 95%CI 1.06-1.37). Conversely, decreased chemotherapy use was associated with age ≥76 (OR=0.24; 95%CI 0.2-0.27), being single (OR=0.76; 95%CI 0.67-0.86), and higher comorbidity score (OR=0.69; 95%CI 0.61-0.78). Among chemotherapy-treated patients, 3,808 (73.8%) received it in the adjuvant setting, 722 (14.0%) received it in the neoadjuvant setting, and 629 (12.2%) received chemotherapy both preoperatively and postoperatively. Among those who were treated with any chemotherapy, the percentage of patients treated with neoadjuvant chemotherapy increased from 15.2% in 2010 to 37.4% in 2017 (p< 0.001). Among patients treated with chemotherapy, neoadjuvant chemotherapy use was associated with recent year of diagnosis (OR=3.38; 95%CI 2.77-4.12), regional stage (OR=3.28; 95%CI 2.86-3.77), and inversely associated with older age (OR=0.77; 95%CI 0.64-0.94), non-White, non-Hispanic, non-Black race or ethnicity (OR=0.64 95%CI 0.45-0.94), non-metro area (OR=0.61; 95%CI 0.5-0.74), and Northeastern region (OR=0.66; 95%CI 0.56-0.78). Conclusion: Our study highlights the significant changes in patterns of adjuvant and neoadjuvant chemotherapy use among elderly patients with early-stage TNBC. We observed an increasing trend in chemotherapy utilization, with a notable shift from adjuvant to neoadjuvant treatment. This transition reflects the evolving landscape of cancer care and the adoption of more personalized approaches to treatment, with increased utilization of neoadjuvant chemotherapy offering opportunities for better risk assessments and tailored treatment strategies. Citation Format: Catalina Malinowski, Xiudong Lei, Sharon Giordano, Marianna Chavez. Patterns of Chemotherapy Utilization among Elderly 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 PO3-03-07.

Abstract PO2-03-11: A novel peripheral CD4+ T cell immune network associated with response to PD-1 inhibitor in early-stage triple negative breast cancer

Abstract A novel peripheral CD4+ T cell immune network associated with response to PD-1 inhibitor in early-stage triple negative breast cancer Background: Immunotherapy has showed benefits in early-stage triple-negative breast cancer (eTNBC). However, there is an urgent need to identify novel biomarkers that can guide stratification for immunotherapy in eTNBC. Anti-tumor immunity is a systemic response that encompasses the mobilization of dendritic cells, lymphocytes, and myeloid cells involving the tumor, blood, and lymph nodes. The activation of anti-tumor immune responses via immunotherapy is expected to reflect in the subset change of circulation. Combined with advantage of dynamic monitoring by liquid biopsy, we detected peripheral blood in the eTNBC patients under immunotherapy to explore potential immune therapeutic predictive subsets. Methods: Single-cell (sc) RNA sequencing was utilized to determine the transcriptomics of immune cells in the peripheral blood. Meanwhile scTCR sequencing was used to trace the dynamic changes of clonetypes under multi-therapy. Nanostring analysis of primary tumor and in vivo models were used to validate the mechanism of immune crosstalk. Prediction index was built based on the proportion of immune subsets at each time point and change of tumor size in each patient. Results: 12 eTNBC patients who participated in neoadjuvant chemotherapy in combination with PD-1 inhibitor (Toripalimab) clinical trial were included in this study. The clinical trial consists of two stages. All eligible patients received four cycles of EC (cyclophosphamide plus epirubicin) regimen and followed four cycles of nab-paclitaxel plus PD-1 inhibitor. Among the 12 patients, 5 patients achieved pCR, while the remaining 7 patients were non-pCR. Peripheral blood samples were collected at baseline, after chemotherapy induction, and on PD-1 inhibitor treatment for scRNA- and scTCR-sequencing. Through prediction index, a novel predictive pattern based on ratio of memory T cells (central memory T and resident memory T) to effective T cells in the peripheral was vividly defined, by which the patients could be classified into C-type (memory T cells dominated) and E-type (effective T cells dominated). The C-type indicated better efficacy of immunotherapy combination therapy, while the E-type suggested better efficacy of chemotherapy alone. Meanwhile, a novel peripheral CD4+Trm (resident-memory-like) subset that possessed both strong differentiation potential and memory function was higher in pCR group at baseline. TCR-tracing analysis revealed that the new clones induced by chemotherapy mainly belong to the CD4+ Trm and CD8+ CD161+ Tcm (central memory) subsets, and the upregulation of CD8+ CD161+ Tcm during therapy was a dynamic predictor for immunotherapy benefits. Besides, most of CD4+Trm transitioned into CD4+Th1-like cells as an activated status, which considered CD4+Trm as a group of reservoirs with polyclonality and differentiation potential for tumor-killing. Meanwhile, the increase in CD5+ cDC2 (type 2 conventional dendritic cell) after chemotherapy was associated with enhanced antigen-presenting function and cell communication and co-stimulation with CD4+ Trm cells which helped the activated transition from CD4+Trm into CD4+Th1-like cells in lymph nodes. Moreover, CD4+Th1-like cells increased secretion of Th1 cytokines thus leading to promote CD8+CD161+ Tcm upregulation and tumor-infiltration after immunotherapy. Conclusions: A novel peripheral pattern based on subsets of T cells as C-type and E-type was established as potential predictors for immunotherapy stratification in eTNBC patients. Meanwhile, a novel peripheral CD4+Trm immune network was identified, in which CD5+cDC2 activated the transition of CD4+Trm into CD4+Th1-like subset leading to activation and tumor-infiltration of CD8+CD161+Tcm. All the above provided potential therapeutic targets for enhancing immunotherapy. Citation Format: Zehao Wang, Zhibo Shao, Bingqiu Xiu, Jiong Wu. A novel peripheral CD4+ T cell immune network associated with response to PD-1 inhibitor 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 PO2-03-11.

Abstract PS16-07: Tumor infiltrating lymphocyte stratification refines AJCC TNM staging based outcomes of early-stage triple negative breast cancer treated with neoadjuvant anthracycline-free, docetaxel and carboplatin chemotherapy

Abstract Background: Stromal tumor-infiltrating lymphocytes (sTILs) quantification is associated with pathological response to neoadjuvant chemotherapy (NAC) and long term outcomes in setting of adjuvant anthracycline based chemotherapy. A previous study in TNBC patients treated with adjuvant anthracycline chemotherapy shows that at a cut point of 30%, sTILs can up and downstage traditional AJCC stage groups. Additive impact of sTILs on refining outcomes beyond pathological response and TNM stage for patients treated with anthracycline-free chemotherapy is not known. This study aimed to investigate impact of sTILs on outcomes in a large cohort of TNBC patients treated with Docetaxel plus carboplatin NAC. Methods: Patients with stage I (T size > 1cm) to III TNBC scheduled to receive 6 cycles of NAC docetaxel (75 mg/m2) plus carboplatin (AUC 6) (TCb) every 3 weeks from two studies (NCT01560663 and NCT02302742) were combined for this analysis. sTILs were evaluated on pre-treatment H&E slide using standard criteria centrally by one of the investigators (RS). Pathological complete response (pCR) was defined as ypT0/is ypN0. Logistic regression analysis was used to examine the effect of multiple variables on Event free survival (EFS) and overall survival (OS). Results: For 474 patients included in this analysis, median age was 52 years, 8% were Black, 13% had germline BRCA1/2 mutation, 44% had clinical Lymph node (LN) positive disease and 13%, 62% and 25% respectively had TNM stage I, II and III disease. Median sTILs were 5% (range 1-95%) and 25% had >30% sTILs. pCR and RCB 0+1 rates were 50.2% and 60.4% respectively. On multivariable analysis, T stage (OR=0.51, p=0.030), nodal status (OR=0.56, p=0.028), Ki67 (OR=2.74, p< 0.001) and sTILs (OR=2.01, p=0.014) were associated with pCR. pCR rate in those with sTILs < 30 vs sTILs >30 was 45.9% and 63.9% respectively (p=0.0014). At median follow-up of 58 months, 5 years EFS was 81.05% in all patients, 93.94% in those with pCR and 68.67% in those without pCR, 5 year OS was 84.83% in all patients, 96.53% in those with pCR and 74.13% in those with residual disease. On multivariate analysis lower T stage, negative LN status and increasing sTILS were associated with better EFS (T stage: HR =1.98, p=0.018; LN status: HR=2.92, p< 0.001; sTILs: HR:0.46, p=0.04) and OS (T stage: HR=1.89, p=0.040; LN status: HR=3.13, p=0.001; sTILs: HR=0.30, p=0.008). At a cut-point of 30%, sTILs up and downstaged anatomic AJCC TNM stage groups (table 1). Conclusions and Relevance: In patients treated with anthracycline-free TCb chemotherapy, sTILs were independent predictors of EFS and OS beyond clinicopathological features. Notably, 30% sTILs cut-point stratified outcomes beyond anatomical TNM staging. These, findings can aid in patient stratification for chemotherapy backbone de-escalation in future trials and have the potential to inform patient selection for adjuvant treatment escalation and de-escalation trials. Tumor infiltrating lymphocyte stratification refines AJCC TNM staging based outcomes of early-stage triple negative breast cancer treated with neoadjuvant anthracycline-free, docetaxel and carboplatin chemotherapy. Table. Citation Format: Miguel Martín, Rachel Yoder, Roberto Salgado, María del Monte-Millán, Enrique Álvarez, Isabel Echavarria, Joshua Staley, Coralia Bueno-Muiño, Yolanda Jerez Gilarranz, Andrew Godwin, María Cebollero, Oscar Bueno, José Ángel García-Sáenz, Fernando Moreno Antón, Uriel Bohn, Henry L Gómez, Tatiana Massarrah, Sara López-Tarruella, Priyanka Sharma. Tumor infiltrating lymphocyte stratification refines AJCC TNM staging based outcomes of early-stage triple negative breast cancer treated with neoadjuvant anthracycline-free, docetaxel and carboplatin chemotherapy [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 PS16-07.

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 RF02-07: Precocious modulation of metabolic and immunological parameters predicts tumor response to fasting-mimicking diet plus chemotherapy in patients with early stage TNBC

Abstract Background: Preclinical studies showed that severely calorie restricted fasting-mimicking diets (FMDs) enhance the antitumor efficacy of chemotherapy (CT) or immunotherapy (IO) in murine triple negative breast cancer (TNBC) models. These effects are mediated by a combination of blood glucose reduction and positive immunomodulatory effects. Moreover, combining fasting and metformin produced synergistic anticancer effects in a broad range of tumor models. The BREAKFAST trial was designed to investigate if FMD, plus/minus metformin, could increase the antitumor activity of neoadjuvant CT in patients with stage I-III TNBC. Methods: BREAKFAST (NCT04248998) is a randomized, non-comparative, phase II, pilot trial that enrolled stage I-III (cT>1 cm) TNBC patients (pts) candidate to receive 4 cycles of neoadjuvant CT with doxorubicin-cyclophosphamide every 3 weeks, followed by 12 cycles of weekly paclitaxel. Pts were randomized 1:1 to receive: CT plus 5-day FMD every 3 weeks, up to 8 cycles (arm A); CT plus FMD plus daily metformin (1700 mg) (arm B). The primary study endpoint was the rate of pCR in either experimental arm. Secondary/exploratory endpoints included safety, compliance, and biomarker analyses based on blood metabolomics and tumor transcriptomics analyses at different timepoints. Results: Between June 2020 and February 2022 we enrolled 30 pts. Then, the study was interrupted after the introduction of chemo-immunotherapy (CT-IO) as a standard neoadjuvant therapy for early stage TNBC pts. Among 30 pts, 13 were treated with CT plus FMD, while 17 pts received CT plus FMD plus metformin. Overall, pCR rate was 56.6%, i.e., significantly higher than pCR rates reported with anthracycline-taxane CT alone in previous phase II/III trials (26-39%), with no significant differences among treatment arms (p=0.49). The FMD acutely reduced blood glucose, insulin and LDH levels, which reflects a reduction in systemic and/or tumor glucose metabolism. Of note, precocious LDH reduction was more pronounced in patients undergoing pCR. RNA-seq analysis of tumor samples revealed a significant downmodulation of glycolysis and TCA cycle pathways after one treatment cycle, paralleled by an increase of intratumor activated T cells, memory T cells and NK cells, as estimated by deconvolution analyses of tumor transcriptomic data. Of note, these changes were observed only in patients achieving pCR. While intratumor metabolic changes were similar in the two treatment arms, the modulation of intratumor immunity was more pronounced in patients not receiving metformin. Conclusion: Preoperative CT plus cyclic FMD (plus/minus metformin) results in excellent pCR rates in localized TNBC patients. Early on-treatment downregulation of systemic and intratumor metabolic parameters related to glucose metabolism predicts pCR, and this is independent of metformin use. Based on results of this study, we recently initiated a large, multicentric trial, namely the BREAKFAST-2 (NCT05763992) study, which will investigate if adding cyclic FMD to neoadjuvant CT-IO increases pCR rates in ~ 145 pts with stage II-III TNBC. Citation Format: Francesca Ligorio, Giovanni Fucà, Andrea Vingiani, Fabio Iannelli, Riccardo Lobefaro, Leonardo Provenzano, Lucrezia Zanenga, Cristina Ferraris, Antonino Belfiore, Silvia Brich, Alessia Bertolotti, Gianfranco Scaperrotta, Catherine Depretto, Antonia Martinetti, Elisa Sottotetti, Paola Antonia Corsetto, Giulia Valeria Bianchi, Giuseppe Capri, Secondo Folli, Saverio Minucci, Marco Foiani, Massimiliano Pagani, Giancarlo Pruneri, Filippo De Braud, Claudio Vernieri. Precocious modulation of metabolic and immunological parameters predicts tumor response to fasting-mimicking diet plus chemotherapy in patients with early stage 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 RF02-07.

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 PO2-13-04: Single cell characterization of senescent CD8+ T cell promotes immunotherapy resistance in early-stage triple-negative breast cancer

Abstract Background: Immune checkpoint blockade (ICB) has been explored in triple-negative breast cancer (TNBC) and has been proven to improve patient survival in advanced TNBCs (IMpassion130) or increase the pathological complete response rate in early TNBCs (KEYNOTE522). However, ICB could only benefit a subset of patients, highlighting the urgent need to optimize patient selection. Unlike in advanced TNBCs, a predictive biomarker for ICB in early TNBCs is still lacking. The main reason might be that previous studies neglected the heterogeneity of tumor ecosystems between early and advanced TNBCs. There is an urgent need to understand the unique ecosystem of early-stage TNBC and develop biomarkers for precision immunotherapy. Objective: This study aims to characterize the micro-loop associated with the immune efficacy of early TNBC, so as to explain the mechanisms behind the differences in early and late efficacy markers, identify efficacy markers in early TNBC immunotherapy, and search for clinical targeting strategies to sensitize TNBC for neoadjuvant therapy. Methods: We conducted an in-depth analysis of 32 single-cell transcriptomes, comprising 26 early-stage TNBC enrolled in prospective clinical trials (NCT04418154 and NCT04613674), receiving neoadjuvant chemotherapy alone (n=8) or combined with anti-PD1 (n=18), and 6 advanced TNBC. We analyzed the microenvironmental differences between early and advanced tumors, and between different treatment response groups in early stages, and identified a subpopulation of cells specific to early stages and associated with immunotherapeutic efficacy. We used mIHC, flow-through, and validated the presence of this cell in clinical samples. We also explored its predictive performance on four independent cohorts of TNBCs with ICB treatment (GSE194040, NCT04129996, GSE169246, GSE124821). Furthermore, to understand the impact of ISG+ T cells on immunotherapy efficacy and explore targeting strategies, we employed a multi-faceted approach to assess their tumor-killing ability, response to Anti-PD1 treatment, and sensitization effect of drugs targeting ISG+ T cells. ISG+ T cells were sorted using flow cytometry for further experiment. In vitro, we established a co-culture model of primary TNBC patients-derived organoid (PDO) and tumor infiltrated CD8+T cells and evaluated the tumor cell viability as well as T cell cytotoxicity. In vivo, we established TS/A tumor cell bearing BalB/c mouse and E0771 tumor cell-bearing C57BL mouse and measured tumor size and tumor microenvironment by flow cytometry. Results: We obtained 236,017 high-quality cells and identified cell subsets across 32 samples with different stages, treatments and responses. We then uncovered an enriched subset of interferon-induced (ISG+) CD8+ T cells specific to early TNBC, serving as a predictive factor for ICB resistance. Mechanistically, the upregulation of the IFN pathway in early-stage TNBC triggers a transition in ISG+ CD8+ T cells, resulting in cellular senescence, diminished cytotoxicity, and impaired response to ICB. Encouragingly, we made a noteworthy discovery that Nicotinamide mononucleotide, an anti-aging drug, effectively restores the functionality of ISG+ CD8+ T cells, amplifying immunotherapy sensitivity. Conclusions: This study provided a comprehensive single-cell transcriptome atlas of early-stage TNBC and depicted stage-related ISG+CD8+ T cell for predicting ICB response in early TNBC. We emphasize the critical role of T cell dysfunction prompted by cellular senescence in driving ICB resistance during the early stages of TNBC and propose an approach for sensitizing immunotherapy with aging drugs. Citation Format: Tong Fu, Yi-Yu Chen, Xi Jin, Yi-Zhou Jiang, Zhi-Ming Shao. Single cell characterization of senescent CD8+ T cell promotes immunotherapy resistance 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 PO2-13-04.

Abstract PO2-15-08: Exploring Essential Immune Genes Linked to Pathological Complete Response and Survival in Early-Stage Triple-Negative Breast Cancer (TNBC) after Chemotherapy Treatment

Abstract Background: De-escalation and escalation of systemic therapy in early-stage TNBC will require the implementation of biomarkers to guide therapy. To date, high expression of a variety of immune genes has been associated with higher pathological complete response (pCR) rates following neoadjuvant chemotherapy or with improved survival, or both, in early-stage TNBC. However, it is currently unknown which are the key genes influencing survival (i.e., the Core Immune Genes [CIG]) and if combinations of these genes can improve their association with both clinical endpoints. Methods: The expression of up to 185 genes was evaluated on pre-treatment tumor biopsies from 3 independent publicly available datasets of early-stage TNBC: CALGB40603 (n=388) (NCT00861705), BrighTNess (n=482) (NCT02032277), and SCAN-B (n=498). Patients in CALGB40603 and BrighTNess were treated with neoadjuvant chemotherapy-based therapy and had response data. Patients in CALGB40603 and SCAN-B had survival outcome data (event-free survival [EFS] or relapse-free interval [RFi]). Each individual gene was associated with each clinical endpoint within each dataset using Cox model and logistic regression analyses, adjusting for treatment arm. Genes found in common across datasets were selected as CIG, except for PDCD1, which was not available in BrighTNess. Using the CIGs, we evaluated whether combinations of 2 genes enhance their association with each clinical endpoint using different methods: adding, subtracting, multiplying, and ratio. Likelihood ratio testing was used to evaluate the added contribution of each gene in 2 combined cohorts evaluating pCR (i.e., CALGB40603 and BrighTNess) and survival (i.e., CALGB40603 and SCAN-B). Results: 10 CIGs related to B-cells and T-cells (i.e., IRF4, LAX1, POU2AF1, CD274, CD79A, TNFRSF17, PIM2, PDCD1, CXCR6, and SLAMF1) were associated with higher pCR rates and improved survival outcome across datasets. Of note, 5 (50%) genes are known components of the 14-gene immunoglobulin/B-cell (IGG) signature. The correlation coefficient among the 10 CIG genes was 0.63 (moderate). In general, the sum of 2 CIGs provided more prognostic information than a single gene (p< 0.001). Specifically, the sum of 2 CIGs provides more prognostic information than a single gene in 30 of 45 (66.6%) cases. Two-gene subtraction, multiplication or ratio decreased the amount of prognostic information (p< 0.001). The top 10 2-gene CIGs associated with prognosis (p< 0.001) were CD274_TNFRSF17, IRF4_CD274, PDCD1_TNFRSF17, CD79A_CD274, CD274_POU2AF1, CXCR6_TNFRSF17, LAX1_TNFRSF17, SLAMF1_TNFRSF17, CD274_LAX1 and CD79A_CXCR6. In general, the sum of 2 CIGs provided more information about pCR than a single gene (p< 0.001). Specifically, the sum of 2 CIGs provided numerically more information about pCR than 1 gene in 17 of 36 (47.2%) cases. Two-gene subtraction, multiplication or ratio decreased the amount of information about pCR (p< 0.001). The top 10 2-gene CIGs associated with pCR were CD274_PIM2, CD274_POU2AF1, CXCR6_PIM2, CD274_CXCR6, IRF4_CD274, CXCR6_POU2AF1, CD274_LAX1, IRF4_CXCR6, CXCR6_LAX1, and POU2AF1_SLAMF1. Conclusion: The expression of CIGs associated with B-cell and T-cell adaptive immune response is closely linked to pCR and survival outcomes following (neo)adjuvant chemotherapy. When combining the expression of 2 specific CIGs through addition, we found that this method provides more informative insights into pCR and survival outcomes compared to other combination methods. This approach enhances the predictive power of CIGs, enabling a better understanding of treatment response and patient prognosis, ultimately contributing to improved clinical decision-making and patient outcomes. Citation Format: Fara Brasó-Maristany, Laia Paré, Benedetta Conte, Laura Angelats, Ana Vivancos, Joel S Parker, Charles M. Perou, Patricia Villagrasa, Aleix Prat. Exploring Essential Immune Genes Linked to Pathological Complete Response and Survival in Early-Stage Triple-Negative Breast Cancer (TNBC) after Chemotherapy Treatment [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 PO2-15-08.

Abstract PO3-03-08: Use of adjuvant Capecitabine after neoadjuvant chemotherapy: A Cohort Study among Elderly Patients with Early-Stage Triple-Negative Breast Cancer

Abstract Background: The use of capecitabine in the adjuvant setting in patients with residual disease after neoadjuvant chemotherapy has been incorporated into practice based on the results of the CREATE-X trial. We evaluate utilization patterns of adjuvant capecitabine use, its association with outcomes, and subsequent hospitalizations and emergency room (ER) visits among elderly patients with early-stage triple-negative breast cancer (TNBC). Methods: We identified patients aged ≥66, diagnosed with early-stage TNBC between 2010 and 2017 in the SEER and Texas Cancer Registry (TCR)-linked Medicare databases. All patients were treated with neoadjuvant chemotherapy for localized or regional-stage disease. All patients had continuous enrollment in Medicare Parts A & B without a Health Maintenance Organization enrollment 12 months before cancer diagnosis and 12 months after cancer diagnosis. Chemotherapy administration was identified using HCPCS codes from outpatient and physician’s carrier claims. We analyzed the patterns of capecitabine use, its association with survival outcomes, and the frequency of ER visits and hospitalizations during treatment (between the first capecitabine claim and 30 days after the last claim for capecitabine). Descriptive statistics were used. Primary analyses included logistic regression, Kaplan-Meier estimates, and Cox regression models with propensity score adjustments. This study adhered to the STROBE guidelines for cohort studies. Results: 1,239 patients with localized or regional TNBC treated with neoadjuvant chemotherapy were included (median 72 years). Of them, 96 (7.7%) were prescribed adjuvant capecitabine. Treatment with capecitabine was associated with recent year of diagnosis, regional disease, and residing in non-metropolitan areas. Specifically, the use of capecitabine increased from 1% in 2010 to 10% in 2016 and 21% in 2017. The median duration of capecitabine treatment was 4 cycles. In multivariable logistic regression analyses, older age was associated with decreased odds of receiving ≥4 cycles of capecitabine (OR=0.25; 95% CI: 0.11–0.60; p =0.002). Among capecitabine users, 3-year OS was 46% and 78% for patients who received 1-3 and ≥4cycles of capecitabine, respectively (p< 0.001). The 3-year estimate of BCSS was 43% and 85% respectively (p< 0.001). After multivariable adjustment for comorbidity score, stage, and propensity score, receiving ≥4 cycles of capecitabine was associated with decreased risk of death (HR=0.29; 95%CI 0.13–0.63, p=0.002) and breast cancer-specific death (HR=0.15; 95%CI: 0.05–0.51, p=0.002) compared to receiving 1-3 cycles. Twenty-seven (28%) patients had ER/hospitalization during capecitabine treatment; median time from initial capecitabine claim to ER/hospitalization was 24 days (IQ 13-39). The median number of capecitabine cycles was 3 (IQR 2-5) and 5 (IQR 3-8) for those with and without ER/hospitalization (p=0.02). The most common diagnosis codes associated with ER/hospitalization included pleural effusion, GI symptoms, pneumonia, and acute kidney failure. A higher comorbidity score at diagnosis was associated with an increased risk of ER/hospitalization (HR=2.76; 95%CI 1.05-7.28, p=0.04). Conclusion: We demonstrate an increasing trend in capecitabine utilization among elderly patients with early-stage TNBC. Although the limited sample size hindered a conclusive analysis, more cycles of capecitabine were associated with improved survival outcomes. Notably, a significant proportion of patients undergoing capecitabine treatment experienced ER/hospitalizations. These findings contribute valuable information on the risks and benefits of capecitabine treatment, aiding evidence-based decision-making to prevent serious complications. Citation Format: Marija Sullivan, Xiudong Lei, Catalina Malinowski, Sharon Giordano, Marianna Chavez. Use of adjuvant Capecitabine after neoadjuvant chemotherapy: A Cohort Study among Elderly 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 PO3-03-08.

Abstract PO4-08-10: Genetic mutations and associated rates of pathologic complete response among a diverse patient population with early stage triple negative breast cancer

Abstract Background: Combination treatment with chemotherapy and immunotherapy remains the standard of care for high risk, early-stage triple negative breast cancer (TNBC). Although the addition of immunotherapy improves rates of pathologic complete response (pCR) and event-free survival, approximately 50% of patients achieve pCR with neoadjuvant chemotherapy alone suggesting that some patients may safely avoid the potential toxicities of immunotherapy without compromising outcomes.1,2 Markers of immune activation including PD-L1 expression and tumor infiltrating lymphocytes have demonstrated prognostic significance; however, identifying a predictive biomarker to aid in selecting those patients most likely to benefit from immunotherapy remains an unmet need.3,4 Genetic mutations are suggestive of DNA susceptibility to damage and the role they may play as a potential marker of immune response is unclear.5,6 This study explores genetic analysis and mutation rates among a diverse cohort of patients with TNBC to identify patterns associated with and without pCR. Methods: We evaluated 105 women diagnosed with Stage I-III TNBC and treated with combination neoadjuvant chemotherapy and immunotherapy at Ochsner Cancer Center between December 2019 through June 2022. Exclusion criteria included ER+, PR+, HER2+, or unknown receptor status, no pembrolizumab in the neoadjuvant setting, no definitive surgery following neoadjuvant treatment, absence of documented race and age less than 18 years of age. Data was collected utilizing Epic Slicer Dicer program, in addition to chart review. Genetic analysis was performed using a variety of DNA-based next generation sequencing analysis platforms. Results: 91 patients met inclusion criteria. 17 patients were found to have pathogenic mutations (BRCA1/2, POLE and ATM), 38 patients had variants of undetermined significance (VUS) and 36 patients had neither. Among patients with pathogenic genetic mutations, 81.25% had a pCR following neoadjuvant treatment compared to 58.33% of those with a VUS and 47.06% of those with no known mutation (p=0.07). Before adjusting for age and stage, patients with a pathogenic mutation were 73% more likely to achieve pCR than those with no known genetic mutations (crude RR: 1.73, 95% CI: 1.13-2.65). After adjusting for age and stage, the relationship was not statistically significant (aRR: 1.15, 95% CI: 0.78-1.34). Among the 47 Black patients, 5 were found to have a pathogenic mutation and 29 had a VUS. 11 of the 39 White patients were found to have a pathogenic mutation while only 6 had a VUS. Across all genetic mutation categories, Black patients experienced lower rates of pCR than White patients. White patients with a known pathogenic mutation had the highest rate of pCR at 90.91%, while Black patients with no identified mutation had the lowest rate of pCR at 38.46%. The generalizability of these results may be limited due to small sample size. Conclusion: Our results demonstrating higher rates of genetic variants among patients achieving pCR regardless of race highlight the importance of better understanding how these variants correlate with tumor mutational burden (TMB) and further, the role this may play in predicting immune-response. Larger studies are needed to assess TMB as a predictive biomarker in early-stage TNBC as this may provide opportunities to further individualize treatment and minimize toxicity among this group of patients. Additionally, given differences in the prevalence of pathogenic mutations and VUS among Black patients, better understanding the relationship between mutation status and immune response is imperative to optimize outcomes in this high-risk population. Table. Citation Format: Caitlin Taylor, Melanie Sheen, Rabia Cattie, Victoria Chung, Melyssa Bratton, Meredith Lakey, Erin Biggs. Genetic mutations and associated rates of pathologic complete response among a diverse patient population 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 PO4-08-10.

Abstract GS01-03: Adding atezolizumab to adjuvant chemotherapy for stage II and III triple-negative breast cancer is unlikely to improve efficacy: interim analysis of the ALEXANDRA/IMpassion030 phase 3 trial

Abstract Background: Early stage triple negative breast cancer (TNBC) is associated with a high risk of distant relapse. ALEXANDRA/IMpassion030 is a global, prospective, randomized, open-label, phase 3 trial that investigated the efficacy, safety and pharmacokinetic profile of adjuvant atezolizumab plus standard anthracycline/taxane chemotherapy (arm A) versus chemotherapy alone (arm B) in early-stage TNBC. Methods: ALEXANDRA/IMpassion030 (NCT03498716) aimed to randomize (1:1) 2300 patients with operable stage II-III TNBC, confirmed by central pathology review. Patients were stratified by type of surgery (breast conserving versus mastectomy), nodal status (0 versus 1-3 versus >=4 nodes), and centrally assessed PD-L1 status (IC 0 vs >=1% ). Adjuvant chemotherapy consisted of weekly paclitaxel 80 mg/m2 for 12 weeks followed by dose dense anthracycline (epirubicin 90 mg/m2 or doxorubicin 60 mg/m2) and cyclophosphamide 600 mg/m2 for 4 doses every 2 weeks given concomitantly with atezolizumab 840 mg every 2 weeks followed by maintenance atezolizumab 1200 mg every 3 weeks until completion of 1 year of atezolizumab (Arm A) or the same chemotherapy regimen (T-EC/AC) alone (Arm B). The primary endpoint was invasive disease-free survival (iDFS); secondary endpoints included, iDFS in the PD-L1 positive and lymph node-positive subpopulations, overall survival, safety, patient functioning and health related quality of life (HRQoL). On the 14th of November 2022, following an IDMC recommendation, the study accrual was temporarily stopped. In February 2023, the protocol was amended in order for the IDMC to perform an early interim analysis of efficacy and futility, at approximately 62% of the planned (390) iDFS events. The futility boundary was set to a Hazard Ratio (HR) > 1. Results: The IDMC recommendations of 15th March 2023 reported that the primary endpoint crossed the futility boundary, accrual to the study was permanently stopped and the experimental treatment was discontinued. Between August 2018 and November 2022, the study enrolled 2199 patients, with 1101 randomised to the atezolizumab arm (A) and 1098 to the control arm (B). At a median follow-up of 25.3 months, 239 (10.9%) iDFS events were observed in the 2199 enrolled patients; 127 versus 112 iDFS events were observed (61.3% of 390) in the A versus B arms respectively, HR 1.12, (95% confidence interval, CI, 0.87, 1.45). In the PD-L1 positive subgroup, (1567/2199 patients, 71.3%), 77 versus 73 iDFS events were observed in the A versus B arms respectively, HR 1.03, (95% CI 0.75, 1.42). Among patients with lymph node positive tumors (1066/2199 patients, 48.5%), 86 versus 66 iDFS events were observed in the A versus B arm respectively, HR 1.41, (95% CI 1.02, 1.96). Incidence of adverse events grade >=3 was 58.01% versus 48.15% in the A versus B arms, including death in 1.01% (11) and 0.55% (6) of patients, respectively. Conclusions: Crossing the pre-specified futility boundary of HR > 1 provides evidence that adjuvant atezolizumab is very unlikely to improve invasive disease-free survival when added to adjuvant anthracycline and taxane based chemotherapy in patients with stage II-III triple-negative breast cancer. With longer treatment exposure in the atezolizumab arm (A), adverse events were more frequent but consistent with the atezolizumab safety profile. No new or unexpected safety issue was identified. Citation Format: Michail Ignatiadis, Andrew Bailey, Heather McArthur, Sarra El-Abed, Evandro de Azambuja, Otto Metzger, Steve Chui, Max Dieterich, Thomas Perretti, Guenther Steger, Jacek Jassem, Soo Chin Lee, Michaela Higgins, José Zarbá, Marcus Schmidt, Henry Gomez, Angel Guerrero-Zotano, Luca Moscetti, Joanne Win Yang Chiu, Carter DuFrane, Vanessa Honvault, Rosa Altarcheh, Luciana Molinero, Andrew Ellingson, Elisabetta Munzone, Noa Efrat Ben-Baruch, Emilio Bajetta, Shinji Ohno, Seock-Ah Im, Gustavo Werutsky, Einav Gal-Yam, Xavier Gonzalez-Farré, Ling-Ming Tseng, William Jacot, Oleg Gluz, Zhimin Shao, Yaroslav Shparyk, Ivan Sinielnikov, Zimina Anastasia, Aleksandr Vasiliev, Esther Shearer-Kang, Eric Winer, Diogo Martins-Branco, Shona Fielding, David Cameron, Giuseppe Viale, Shigehira Saji, Richard Gelber, Martine Piccart. Adding atezolizumab to adjuvant chemotherapy for stage II and III triple-negative breast cancer is unlikely to improve efficacy: interim analysis of the ALEXANDRA/IMpassion030 phase 3 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 GS01-03.

Abstract PO2-13-10: Predicting outcomes in locally advanced breast cancer through profiling post-neoadjuvant tissue-based minimal residual disease

Abstract Background: Neoadjuvant chemotherapy (NAC) for locally advanced breast cancer can down-stage disease prior to surgery, monitor chemo-sensitivity, and provide key prognostic information via pathologic response that guides adjuvant treatment. Greater residual disease as assessed by the residual cancer burden (RCB) index is associated with inferior outcomes but imperfectly predicts recurrence, particularly in triple negative breast cancer (TNBC) where there is heterogeneity of outcomes across RCB scores. As an alternative to RCB and PCR, blood-based minimal residual disease (MRD) from circulating tumor DNA (ctDNA) has been explored. However, poor sensitivity limits ctDNA, which is typically negative post-NAC when treatment decisions are made in patients who later recur. Methods: To address this lack of sensitivity, we developed tissue-based MRD (t-MRD) to assess molecular disease burden in post-NAC breast and lymph node resection tissue. We performed whole exome sequencing on diagnostic tumor and matched germline tissues from five pilot patients with early-stage TNBC with a range of responses to NAC. For each patient, we designed a personalized assay to track tumor-specific SNVs, combined with limited panel of genes recurrently mutated in breast cancer, to enable MRD detection. We then applied this assay to DNA from individual pathology blocks from the tumor resection via ultra-deep targeted hybrid capture. We assessed each sample for the presence of MRD using a Monte Carlo statistical framework to integrate all tumor mutations as previously described (Newman et al, Nature Biotechnology 2016). We aggregated results across all pathology blocks from each case to define each patient’s t-MRD profile and assessed the performance of t-MRD versus gold standard pathologic assessment. Results: We tracked a mean of 136 MRD reporters per case across 119 post-NAC blocks derived from five patients. Twenty-five samples had pathologic residual disease and 28 had detectable t-MRD. There was strong concordance between t-MRD mean allele frequency (AF) and tumor cellularity as assessed by pathology, defined as percent cellularity within the region containing viable tumor (Spearman r = 0.9052, p< 0.0001), and excellent classification of true positive pathology samples by genomic sequencing (AUC = 0.9675, p < 0.0001). Samples (n = 6) where t-MRD but not pathologic residual disease was detected had a lower mean AF than those where there was also histologic residual disease (p=0.0001). Among the five studied cases, we confirmed a molecular complete response with no t-MRD detected in the RCB-0 case (0/44 t-MRD positive blocks). In the two RCB-III cases, we observed more diffuse t-MRD than that assessed by pathology (n = 4 additional blocks with t-MRD but not pathologic disease detected), and in the RCB-II case, we detected minimal t-MRD in only a single block where pathology did not detect residual disease. Significance: By applying blood-based MRD assessment tools to tumor tissue, we developed t-MRD to profile molecular residual disease at the landmark post-NAC timepoint when disease burden is low and adjuvant treatment decisions are made. We demonstrated high concordance with gold standard pathologic assessment, with increased sensitivity and minimal false positive signal. Further studies assessing the additional prognostic value of t-MRD beyond stage-based prognostication and post-NAC RCB scores are ongoing. Citation Format: Julia Ransohoff, Mia Carleton, Alisha Birk, Gregory Bean, Melinda Telli, Ash Alizadeh, James Ford, George Duran, Michael Khodadoust, David Kurtz. Predicting outcomes in locally advanced breast cancer through profiling post-neoadjuvant tissue-based minimal residual disease [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 PO2-13-10.

Abstract PO5-17-01: Pre-treatment tumor infiltrating lymphocytes are associated with higher likelihood of pathologic complete response among black women with TNBC receiving neoadjuvant chemoimmunotherapy

Abstract Background: High risk, early-stage triple negative breast cancer (TNBC) is a heterogenous disease that is associated with early recurrence and high mortality, particularly among black women as compared to their white counterparts. Pathologic complete response (pCR) to neoadjuvant chemotherapy (NACT) is a strong-predictor of long-term disease-free survival in TNBC, and the KEYNOTE-522 trial demonstrated that the addition of immunotherapy (pembrolizumab) to NACT resulted in a higher likelihood of pathologic complete response (pCR) in high-risk early-stage TNBC. Following these findings, the standard of care has been to administer the K522 regimen (K522R) in the neoadjuvant setting for patients with high risk early-stage TNBC. However, our understanding of the clinical and tumor characteristics to prognosticate response to K522 are lacking, and additional real-world data is needed to better understand if these variables differ among race. Methods: We evaluated 76 patients who were treated with the K522R at our institution. There were slides available from 29 patients’ pre-treatment biopsies for pathology review. In the available slides, tumor infiltrating lymphocytes (TIL) were evaluated as the percentage of lymphocytes in the stroma within the tumor area. For the remaining cases that did not have available slides, these variables were retrieved from pathology reports and patients’ charts. Patient characteristics including age, race and body mass index (BMI) were acquired via retrospective chart review. These clinicopathologic variables were correlated with pCR, which was defined by the absence of invasive carcinoma in the breast and axillary lymph nodes at the time of surgery. Binary logistic regression analysis was performed to correlate the above variables with pCR versus residual disease (RD). Results: Seventy-six pre-treatment biopsy specimens treated with the K522R were evaluated. The patient population spanned a broad spectrum of age, body habitus, and race, with mean age 55, mean BMI 28.3, and predominantly black (over 60 percent) population. At the time of analysis, 64 of the 76 patients had completed the K522R and subsequently undergone surgery at our institution. Of the 64 patients who had undergone definitive surgery, 31 (48.4%) achieved pCR. In univariate analysis, pre-treatment TIL was significantly associated with attainment of pCR, with TIL of 28.5% (± 19.1) in patients who achieved pCR versus 9.73% (± 9.40) in those who had RD (95% CI 1.03-1.21, p=0.014*). When TIL was further stratified by race, mean percentage of TIL was significantly higher among black women who achieved pCR (27.5% ± 4.7) compared to black women with RD (12.2% ± 3.05) (95% CI 0.021 – 0.197, p=0.016*). Additionally, mean percentage of TIL was higher overall among black women when compared to the white patients in our cohort, though this finding was not statistically significant (p=0.252). Conclusion: Our real-world data demonstrates high levels of pre-treatment TIL are significantly associated with achievement of pCR in patients with TNBC treated with the K522 regimen. When TIL was further stratified by race, black patients were found to have higher TIL than white patients. Within the black population, a statistically significant difference in TIL percentage was found in those achieving pCR compared to those with RD. It is well understood that black women often have poorer breast cancer outcomes than white women, and our finding of higher TIL percentage among this population, along with the significant association between TIL and attainment of pCR with chemoimmunotherapy, could have important implications for optimization of therapy. Further exploration of this phenomenon in larger, diverse breast cancer populations is warranted. Citation Format: Sarah Wood, Ji-Hoon Lee, Yuan Gao, Xiaoxian Li, Jane Meisel. Pre-treatment tumor infiltrating lymphocytes are associated with higher likelihood of pathologic complete response among black women with TNBC receiving neoadjuvant chemoimmunotherapy [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 PO5-17-01.

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 PO2-20-07: A case report of a severe cutaneous adverse event in triple negative breast cancer treated with chemoimmunotherapy

Abstract Introduction Cutaneous adverse events related to immune checkpoint inhibitors (ICI) are common and most are mild. However, numerous case reports have documented severe ICI-related skin-toxicities such as Stevens-Johnsons Syndrome (SJS) most commonly among patients with melanoma and lung cancer as immunotherapy has now become a mainstay of treatment in these tumors. The use of ICIs in breast cancer treatment has only recently become standard of care for treatment of metastatic and high risk early-stage triple negative breast cancer with the publication of two landmark clinical trials, KEYNOTE-355 and KEYNOTE-522, respectively. While these trials report low rates of severe skin reactions, little is known about ICI-related severe skin toxicities in patients with breast cancer. Case description A 58-year-old female with clinical stage IIB (cT2N0M0) triple negative breast cancer was undergoing neoadjuvant treatment with pembrolizumab, an anti-programmed death (PD-1) monoclonal antibody, coupled with a chemotherapy back-bone of 12 weekly treatments of carboplatin and paclitaxel followed by 4 cycles of doxorubicin and cyclophosphamide. She developed an erythematous and itchy rash on the right breast and axilla approximately 61 days into her treatment course after having received her fourth dose of pembrolizumab. Over the next 10 days, she developed progression of the rash with painful red papules coalescing into reticulated plaques and dusky blistering of the skin involving the right arm, axilla, abdomen, inguinal folds, thigh, and back, totaling < 10% total body surface area. Notably, the rash did not have mucosal involvement. She was hospitalized for close monitoring and treatment. A punch biopsy of the rash revealed interface dermatitis with areas of full thickness skin necrosis consistent with erythema multiforme, SJS, toxic epidermal necrolysis (TEN), or a fixed drug eruption. Her skin continued to slough in the distribution of rash and a diagnosis of SJS was made. The patient had no response to initial treatment with high dose steroids. Cyclosporine was added, resulting in rapid improvement of her rash. The patient’s neoadjuvant treatment was stopped given the grade 3 SJS she experienced. Despite this truncated neoadjuvant treatment, she had excellent clinical response as her tumor was no longer palpable. She proceeded with a partial mastectomy and sentinel lymph node biopsy. Pathology revealed a pathological complete response. She did not receive any further systemic therapy in the adjuvant setting. Three months later, she was evaluated in clinic without evidence of SJS on physical exam. She was rapidly tapered off cyclosporine over one week without recurrence of her rash. Discussion Severe cutaneous adverse events related to ICIs remains an emerging area of study. In SJS, drug-specific CD8+ T lymphocytes utilize granulysin to mediate keratinocyte apoptosis. It is hypothesized that the blocking of the PD-1/PD-L1 interaction by ICIs results in the disruption of T-cell homeostasis leading to self-directed cytotoxic and inflammatory reactions and ultimately epidermal detachment. In contrast, Molina et al 2020 postulate that such ICI-related skin reactions may represent a separate clinical entity from SJS. In their case report of seven patients, they propose the term “progressive immunotherapy-related mucocutaneous eruption” (PIRME), which the authors suggest is characterized by delayed symptom onset, mild initial presentation, rare ocular involvement, benign clinical course, and favorable treatment response. Further characterization of ICI-related cutaneous adverse events is needed to understand the disease course, optimal treatment, and importantly, implications for re-challenging patients with immunotherapy. Clinicians taking care of breast cancer patients treated with ICIs need to be educated to recognize the associated skin toxicities as patients can rapidly worsen without appropriate treatment. Citation Format: Annie Zhang, Mara Beveridge, Bahar Moftakhar. A case report of a severe cutaneous adverse event in triple negative breast cancer treated with chemoimmunotherapy [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 PO2-20-07.