Standard Chemotherapy Research Articles

Impact of Neoadjuvant Chemoimmunotherapy on Surgical Outcomes and Time to Radiation in Triple-Negative Breast Cancer.

We examined the association between immunotherapy-containing and standard chemotherapy regimens with treatment delays and postoperative complications in stage II-III triple-negative breast cancer. The effect of immune-related adverse events (irAEs) was compared. We compared 139 women treated with neoadjuvant pembrolizumab plus chemotherapy (KEYNOTE-522 regimen) from August 2021 to September 2022 with 287 consecutive patients who received neoadjuvant chemotherapy alone prior to July 2021 and underwent surgery. Baseline characteristics, time to treatments, and surgical complications were compared using two-sample non-parametric tests. Linear regression evaluated association of irAEs with time to surgery and radiation. Logistic regression identified factors associated with surgical complications. Age, body mass index, race, American Society of Anesthesiologists (ASA) class, and mastectomy rates were similar among cohorts. No clinically relevant difference in time from end of neoadjuvant treatment to surgery was observed [KEYNOTE-522: median 32 (IQR 27, 43) days; non-KEYNOTE-522: median 31 (IQR 26, 37) days; P = 0.048]. Time to radiation did not differ (P = 0.7). A total of 26 patients (9%; non-KEYNOTE-522) versus 11 (8%; KEYNOTE-522) experienced postoperative complications (P = 0.6). In the KEYNOTE-522 cohort, 59 (43%) of 137 patients experienced 82 irAEs; 40 (68%) required treatment. Older age (P = 0.018) and ASA class 4 (P = 0.007) were associated with delays to surgery after adjusting for clinical factors. Experiencing ≥ 1 irAE was associated with delay to radiation (P = 0.029). IrAEs were not associated with surgical complications (P = 0.4). We observed no clinically meaningful difference between times to surgery/adjuvant radiation or postoperative complications and type of preoperative chemotherapy. IrAEs were associated with delay to adjuvant radiation but not with postoperative complications or delay to surgery.

Correlation between small-cell lung cancer serum protein/peptides determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and chemotherapy efficacy

BackgroundCurrently, no effective measures are available to predict the curative efficacy of small-cell lung cancer (SCLC) chemotherapy. We expect to develop a method for effectively predicting the SCLC chemotherapy efficacy and prognosis in clinical practice in order to offer more pertinent therapeutic protocols for individual patients.MethodsWe adopted matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and ClinPro Tools system to detect serum samples from 154 SCLC patients with different curative efficacy of standard chemotherapy and analyze the different peptides/proteins of SCLC patients to discover predictive tumor markers related to chemotherapy efficacy. Ten peptide/protein peaks were significantly different in the two groups.ResultsA genetic algorithm model consisting of four peptides/proteins was developed from the training group to separate patients with different chemotherapy efficacies. Among them, three peptides/proteins (m/z 3323.35, 6649.03 and 6451.08) showed high expression in the disease progression group, whereas the peptide/protein at m/z 4283.18 was highly expressed in the disease response group. The classifier exhibited an accuracy of 91.4% (53/58) in the validation group. The survival analysis showed that the median progression-free survival (PFS) of 30 SCLC patients in disease response group was 9.0 months; in 28 cases in disease progression group, the median PFS was 3.0 months, a statistically significant difference (χ2 = 46.98, P < 0.001). The median overall survival (OS) of the two groups was 13.0 months and 7.0 months, a statistically significant difference (χ2 = 40.64, P < 0.001).ConclusionsThese peptides/proteins may be used as potential biological markers for prediction of the curative efficacy and prognosis for SCLC patients treated with standard regimen chemotherapy.

Pathological complete response with FOLFIRINOX therapy for recurrence of pancreatic acinar cell carcinoma.

Pancreatic acinar cell carcinoma (PACC) is a very rare subtype of pancreatic cancer. Due to small number of patients, no standard chemotherapy protocol has been established. We experienced an extremely rare case of PACC with liver metastasis that showed a pathological complete response after modified FOLFIRINOX (mFFX) therapy. A 42-year-old man who underwent distal pancreatectomy for an 80mm tumor at the pancreatic tail 3years ago was referred to our hospital in September 2017 for the treatment of a recurrent liver tumor. Percutaneous biopsy revealed an acinar-neuroendocrine carcinoma, similar to the surgical specimen. He received eight cycles of irinotecan plus cisplatin chemotherapy. However, the tumor increased in size, and treatment was switched to mFFX therapy. The tumor in the liver shrank remarkably after nine cycles of mFFX therapy. Conversion surgery was selected, and the patient underwent hepatic left and caudate lobectomy 8months after administration of mFFX. The resected specimen showed no viable tumor cells, indicating a pathological complete response. The histological diagnosis was reconsidered, and PACC was finally diagnosed via an additional immunohistological review. The patient has remained well with no recurrence for 6years after surgery. This study is the first to report a case of pathological complete response with mFFX therapy for the recurrence of PACC.

Strategies to address recruitment to a randomised trial of surgical and non-surgical treatment for cancer: results from a complex recruitment intervention within the Mesothelioma and Radical Surgery 2 (MARS 2) study.

Recruiting to randomised trials is often challenging particularly when the intervention arms are markedly different. The Mesothelioma and Radical Surgery 2 randomised controlled trial (RCT) compared standard chemotherapy with or without (extended) pleurectomy decortication surgery for malignant pleural mesothelioma. Anticipating recruitment difficulties, a QuinteT Recruitment Intervention was embedded in the main trial phase to unearth and address barriers. The trial achieved recruitment to target with a 4-month COVID-19 pandemic-related extension. This paper presents the key recruitment challenges, and the strategies delivered to optimise recruitment and informed consent. A multifaceted, flexible, mixed-method approach to investigate recruitment obstacles drawing on data from staff/patient interviews, audio recorded study recruitment consultations and screening logs. Key findings were translated into strategies targeting identified issues. Data collection, analysis, feedback and strategy implementation continued cyclically throughout the recruitment period. Secondary thoracic cancer care. Respiratory physicians, oncologists, surgeons and nursing specialists supported the trial, but recruitment challenges were evident. The study had to fit within a framework of a thoracic cancer service considered overstretched where patients encountered multiple healthcare professionals and treatment views, all of which challenged recruitment. Clinician treatment biases, shaped in part by the wider clinical and research context alongside experience, adversely impacted several aspects of the recruitment process by restricting referrals for study consideration, impacting eligibility decisions, affecting the neutrality in which the study and treatment was presented and shaping patient treatment expectations and preferences. Individual and group recruiter feedback and training raised awareness of key equipoise issues, offered support and shared good practice to safeguard informed consent and optimise recruitment. With bespoke support to overcome identified issues, recruitment to a challenging RCT of surgery versus no surgery in a thoracic cancer setting with a complex recruitment pathway and multiple health professional involvement is possible. ISRCTN ISRCTN44351742, Clinical Trials.gov NCT02040272.

Survival Outcomes in Stage IV Gastric Cancer Patients with Krukenberg Tumors: A Systematic Review and Meta Analysis.

Stage IV gastric cancer patients with Krukenberg tumors typically exhibit poor survival outcomes, often less than 2years. The management of this tumor subgroup remains non-standardized, and the impact of oophorectomy on survival remains uncertain. In this study, we systematically analyzed survival outcomes among gastric cancer patients with ovarian metastases who underwent standard chemotherapy, surgical resection of ovarian metastases, or combined chemotherapy and surgery. We conducted a systematic reviewand meta-analysis of randomized controlled trials and observational studies retrieved from MEDLINE (PubMed), Embase, and the Cochrane Library until January 25, 2024,applying the Boolean logic. Participants included individuals with pathologically and radiologically confirmed ovarian metastasis or clinically symptomatic cases with imaging evidence. Statistical analyses were performed using R (v.4.3.2., Vienna). The study was registered with PROSPERO(ID-CRD42023488373). A total of 1502 patients from 17 retrospective studies were pooled for analysis of overall survival (OS) outcomes. The OS in the standard chemotherapy cohort, as determined by the random effects model, was 6.708months (95% CI 3.867 to 9.548; P<0.0001), with non-significant heterogeneity (I2 = 5.5%). In the surgical resection cohort, OS was 12.786months (95% CI 6.9 to 18.671; P<0.0001), with low heterogeneity (I2 = 0%). In the combined chemotherapy and surgical resection cohort, OS was 16.228months (95% CI 12.254 to 20.202), with insignificant heterogeneity (I2 = 0%). This meta-analysis offerskey insights into survival outcomes associated with different therapeutic modalities in gastric cancer with Krukenberg metastases. It provides valuable evidence for clinical decision-making and future research directions. While the combined approach of chemotherapy and surgery demonstrates the highest effect size for OS, careful consideration of patient-centric approaches is essential in the oncological care landscape.

PICALM::MLLT10 may indicate a new subgroup of acute leukemias with miscellaneous immunophenotype and poor initial treatment response but showing sensitivity to venetoclax

AbstractThe PICALM::MLLT10 fusion gene is a rare but recurrent event in acute leukemia (AL) associated with poor prognosis. It is still confused whether PICALM::MLLT10 can solely correspond to acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) or acute leukemias of ambiguous lineage (ALAL). Here, we reported a series of PICALM::MLLT10 positive AL patients with miscellaneous immunophenotype including T‐ALL, ALAL, AML, and B‐ALL, complex karyotype, half of extramedullary disease (EMD), frequently concomitant PHF6 mutation, and poor initial treatment response to standard chemotherapy aiming to different immunophenotype, but showing sensitivity to combining chemotherapy especially integrated with venetoclax, suggesting this fusion gene may indicate a new subgroup of AL. Eighteen PICALM::MLLT10 positive patients of 533 AL patients (18/533, 3.4%) were identified by RNA sequencing in our center. We found PICALM::MLLT10 positive AL showing miscellaneous immunophenotype, higher expression of leukemic stemness genes and lower expression of biomarkers of venetoclax resistance, more extramedullary involvement, and especially poor response to conventional induction chemotherapy, but may benefit from venetoclax as well as low‐dose Ara‐C, granulocyte colony‐stimulating factor (G‐CSF), and anthracyclines combination chemotherapy. Sequential hematopoietic stem cell transplantation (HSCT) after chemotherapy combined with venetoclax may further improve long‐term survival in AL patients with complete remission (CR) even measurable residual disease (MRD) positive.

PLAG1 interacts with GPX4 to conquer vulnerability to sorafenib induced ferroptosis through a PVT1/miR-195-5p axis-dependent manner in hepatocellular carcinoma

BackgroundSorafenib is a standard first-line treatment for advanced hepatocellular carcinoma (HCC), yet its effectiveness is often constrained. Emerging studies reveal that sorafenib triggers ferroptosis, an iron-dependent regulated cell death (RCD) mechanism characterized by lipid peroxidation. Our findings isolate the principal target responsible for ferroptosis in HCC cells and outline an approach to potentially augment sorafenib's therapeutic impact on HCC.MethodsWe investigated the gene expression alterations following sgRNA-mediated knockdown induced by erastin and sorafenib in HCC cells using CRISPR screening-based bioinformatics analysis. Gene set enrichment analysis (GSEA) and the "GDCRNATools" package facilitated the correlation studies. We employed tissue microarrays and cDNA microarrays for validation. Ubiquitination assay, Chromatin immunoprecipitation (ChIP) assay, RNA immunoprecipitation (RIP) assay, and dual-luciferase reporter assay were utilized to delineate the specific mechanisms underlying ferroptosis in HCC cells.ResultsOur study has revealed that pleiomorphic adenoma gene 1 (PLAG1), a gene implicated in pleomorphic adenoma, confers resistance to ferroptosis in HCC cells treated with sorafenib. Sorafenib leads to the opposite trend of protein and mRNA levels of PLAG1, which is not caused by affecting the stability or ubiquitination of PLAG1 protein, but by the regulation of PLAG1 at the transcriptional level by its upstream competitive endogenous long non-coding RNA (lncRNA) plasmacytoma variant translocation 1 (PVT1). Data from 139 HCC patients showed a significant positive correlation between PLAG1 and GPX4 levels in tumor samples, and PLAG1 is instrumental in redox homeostasis by driving the expression of glutathione peroxidase 4 (GPX4), the enzyme that reduces lipid peroxides (LPOs), which further leads to ferroptosis inhibition.ConclusionsFerroptosis is a promising target for cancer therapy, especially for patients resistant to standard chemotherapy or immunotherapy. Our findings indicate that PLAG1 holds therapeutic promise and may enhance the efficacy of sorafenib in treating HCC.

Familial and hereditary pancreatic cancer in Japan.

As in Western countries, familial pancreatic cancer accounts for 5-7% of pancreatic cancer (PC) in Japan. Opportunities for diagnosing hereditary pancreatic cancer (HPC) are increasing owing to the coverage of companion diagnostics and cancer genomic profiling by national health insurance in patients with unresectable or recurrent PC refractory to standard chemotherapies. HPC is recognized in 7% of PCs and 15% of familial pancreatic cancer, including germline variants of BRCA1/2, ATM, PALB2, APC, and mismatch repair genes. Individuals with 5-fold or greater inherited risks of PC are recommended to undergo pancreatic surveillance according to Japanese guidelines. The imaging modalities for this surveillance include endoscopic ultrasound, magnetic resonance cholangiopancreatography, abdominal ultrasound, and enhanced computed tomography. Currently, a nationwide prospective surveillance study is ongoing in Japan. Platinum-based chemotherapy is an effective pancreatic cancer treatment in patients with variants of homologous recombination repair genes (BRCA1/2 and PALB2); however, the use of platinum regimens solely based on familial/personal cancer history remains controversial. The efficacy of olaparib maintenance therapy, as confirmed by the POLO study, has significantly impacted the clinical treatment of advanced PC patients in Japan. Since the initiation of precision cancer medicine in 2019, genetic medicine for PC patients has expanded in Japan.

Mitomycin C in the treatment of early triple-negative locally advanced BRCA-associated breast cancer

Rationale. BRCA1 associated triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer. At the same time, carcinomas that develop in carriers of BRCA1 mutations are characterized by extremely high sensitivity to DNA-damaging chemotherapy. Mitomycin C alone or in combination with platinum agents has already demonstrated promising results in the treatment of BRCA-associated ovarian cancer (OC) and metastatic breast cancer. In this article, we present the results of a retrospective study aimed at comparing standard neoadjuvant chemotherapy regimens (NACT) with mitomycin-based regimens for primary locally advanced BRCA1-associated TNBC.The aim of the study is to determine the effectiveness of the combination of mitomycin and platinum compounds during neoadjuvant therapy in patients with primary locally advanced BRCA1 – associated TNBC.Materials and methods. The study included 89 patients diagnosed with primary locally advanced BRCA1-associated TNBC. Patients were divided into three groups depending on the therapy: 1) 4 cycles of anthracycline and cyclophosphamide followed by 12 weekly injections of paclitaxel (n = 48) (AC + T), 2) 4 cycles of anthracycline and cyclophosphamide followed by 12 weekly injections of paclitaxel and carboplatin (n = 27) (AC + TCbP), 3) mitomycin C plus platinum followed by 12 weekly injections of paclitaxel (n = 14) (MR + T). Pathological complete response (pCR) rates were compared.Results. The pCR rate in the MP+T group was 10/14 (71%). In patients with BRCA1-associated breast cancer who received AC + T and AC + TCbP regimens as NACT, the pCR rate was 17/48 (35%) and 19/27 (70%), respectively. The difference in pCR rate between mitomycin-containing therapy and the standard AC + T regimen was statistically significant (p = 0.03); the frequency of regressions was comparable to the frequency in the AC + TCbP group. During the 20-month follow-up period, no relapses were observed in the MR + T group. Relapses were more frequent in the AC + T group compared with the AC + TCbP group (16/48 (33%) vs 1/27 (4%), p = 0.003, Fisher’s exact test). The toxicity profile of the mitomycin-containing regimen included hematologic adverse events, the most common of which were anemia and leukopenia. Compared to standard regimens, nausea was significantly less pronounced. No patients reported alopecia with this regimen.Conclusions. The addition of mitomycin C to neoadjuvant therapy for BRCA1-associated TNBC may be a promising treatment option for this category of patients and merits further study.

Modulators of the Nrf2 Signaling Pathway Enhance the Cytotoxic Effect of Standard Chemotherapeutic Drugs on Organoids of Metastatic Colorectal Cancer.

The activity of known modulators of the Nrf2 signaling pathway (bardoxolone and brusatol) was studied on cultures of tumor organoids of metastatic colorectal cancer previously obtained from three patients. The effect of modulators was studied both as monotherapy and in combination with standard chemotherapy drugs used to treat colorectal cancer. The Nrf2 inhibitor brusatol and the Nrf2 activator bardoxolone have antitumor activity. Moreover, bardoxolone and brusatol also significantly enhance the effect of the chemotherapy drugs 5-fluorouracil, oxaliplatin, and irinotecan metabolite SN-38. Thus, bardoxolone and brusatol can be considered promising candidates for further preclinical and clinical studies in the treatment of colorectal cancer.

Paraneoplastic Hyperthyroidism in advanced testicular non-seminomatous germ cell tumors: Prevalence and clinical Management.

Introduction Paraneoplastic hyperthyroidism (PH) has been reported in patients with testicular germ cell tumors (GCTs), sporadically. This disorder is caused by extremely elevated serum levels of beta-human chorionic gonadotropin (bHCG). To date, little is known about the prevalence of PH, and its clinical features are poorly understood. The aim of the present study was to analyze the relative frequency and clinical features of PH in GCTs and evaluate their effects on therapeutic outcomes. Methods A cohort of 438 patients treated for testicular GCT from to 2017-2023 was retrospectively analyzed for histology, age, clinical stage, and presence of PH. The clinical features of the patients with PH were evaluated descriptively. The relative frequency of PH was compared among the subgroups using descriptive statistical methods. Results Three patients with PH were identified; all had clinical symptoms of hyperthyroidism, suppressed serum levels of thyroid-stimulating hormone (TSH), and increased levels of triiodothyronin (fT3). All the patients had advanced, metastasized, and non-seminomatous (GCTs). Serum bHCG levels ranged from 225,00 U/l to 1,520,000 U/l. The prevalence of PH was 0.7% in the entire GCT population and 60% in those with very high bHCG serum levels. All the patients received standard cisplatin-based chemotherapy along with thyrostatic treatment. The clinical symptoms of the hyperthyroidism rapidly disappeared. Thyroid-stimulating hormone (TSH) levels normalized with decreasing bHCG levels. The PH treatment did not affect the therapeutic outcomes of the patients. Conclusion PH may occur in 0,7% of all patients with GCT, but may be present in up to 60% of patients with very high levels of bHCG. Measuring serum levels of TSH and fT3 should be performed in addition to routine diagnostic measures in all patients with poor prognosis GCTs. Thyrostatic medication is recommended for patients with the clinical symptoms of hyperthyroidism. Early recognition of hyperthyroidism and prompt intervention will reduce comorbidity and help optimize therapeutic outcomes.

Abstract PO3-13-01: ONTARGET: Phase 3 randomized, double-blind, placebo-controlled trial evaluating crofelemer for the prophylaxis of diarrhea in adult patients with solid tumors receiving targeted therapies with or without standard chemotherapy

Abstract Background: Cancer therapy-related diarrhea (CTD) can result in fluid and electrolyte losses, malnutrition, unexpected hospitalization, and poor quality of life (QoL) of patients with cancer. CTD can also limit response to cancer therapy due to treatment interruption, discontinuations, or dose modifications. CTD is a common side effect of targeted therapies (TTx) (e.g., inhibitors of tyrosine kinases, EGFR, CDK4/6, VEGFR) with or without concomitant chemotherapy (ChemoRx) for treating various solid tumors, including breast cancer (BRCA). TTx induce CTD by increasing intracellular cAMP or Ca++ leading to activation of two intestinal Cl- channels, CFTR and CaCC, increasing luminal secretion of Cl- and accompanying loss of Na+ and fluids. For most patients with cancer, CTD management with dietary modifications and antimotility agents is suboptimal. New drugs are needed to prevent or mitigate CTD, a huge unmet medical need. Since the mechanism of CTD is mostly secretory, we hypothesized that crofelemer (CRO) an oral botanical drug purified from the latex of the Croton lechleri tree that modulates both intestinal Cl- ion channels, CFTR and CaCC, may benefit preventing CTD. CRO is negligibly absorbed orally and is FDA-approved for symptomatic relief of noninfectious diarrhea in adults with HIV/AIDS on antiretroviral therapy. In a phase 2 study in 51 women with BRCA receiving THP/TCHP (HALT-D), CRO given daily, compared to standard of care (SOC), for 2 cycles resulted in grade ≥2 diarrhea in significantly fewer subjects (9.0% vs. 33.3%, p=0.0361) in cycle 2 and was 1.8 times more likely to resolve diarrhea (p=0.0425) (Pohlmann et al. 2022; NCT02910219) Methods: ONTARGET (NCT04538625) is a randomized, multicenter, international, double-blind, placebo-controlled pivotal trial evaluating CRO for the prophylaxis of diarrhea in adults with solid tumors receiving 1 of 24 diarrheagenic TTx known to cause any grade diarrhea in ≥50% of patients. This study is designed to show a 40% reduction in loose/watery (LW) stools in patients randomized 1:1 CRO to placebo (1-sided α=0.025) and stratified by tumor type (lung, breast, other) and TTx type (CDK4/6i, TKIs, or other). Eligible patients require a new TTx, ECOG 0-2, lack baseline diarrhea and can complete patient-reported outcome (PRO) diary using a mobile device. Key exclusions include immunotherapy, neratinib or irinotecan (due to required SOC antimotility prophylaxis), colitis/ostomy/abdominal surgery ≤3 months, or antidiarrheal/laxative/antibiotic use ≤7 days. Oral CRO 125 mg or a matching placebo is administered twice daily concomitant with TTx initiation and continued for 12 weeks, with the option to continue blinded treatment through 24 weeks. Rescue antidiarrheal medication is permitted when participants have ≥4 LW stools and can continue thereafter. PRO diaries capture clinical and QoL outcomes. The primary endpoint is the mean weekly number of LW stools over 12 weeks based on PRO diary using the Bristol Stool Form Scale. Key secondary endpoints include time to TTx/ChemoRx dose reduction or discontinuation, time to ≥4 LW stools for 2 consecutive days, fecal incontinence episodes, and time to durable responder status (≤7 LW stools/week). PRO diaries capture: 1) LW stool frequency daily; 2) TTx/ChemoRx dose reduction/discontinuation, use of antimotility drugs, fecal incontinence daily; and 3) CTD’s impact on QoL weekly. Results: Enrollment is complete with 287 patients from 46 sites in 5 countries from 8/2020 through 5/2023. Primary cancer diagnoses were breast (183; 64%), lung (37; 13%), renal (36; 12.5%), liver (12; 4%) and other (19; 6.5%). Most frequent TTx were CDK 4/6 and EGFR inhibitors. To our knowledge this trial evaluating CRO is the first prospective, randomized double blind study for prevention of targeted therapy CTD. Topline results for the study are expected in Q4 2023 and will be reported at the meeting. Funded by Napo Pharmaceuticals (a Jaguar Health Co.) Citation Format: Lee Schwartzberg, Pablo Okhuysen, Eric Roeland, Gregory Vidal, Kathleen Harnden, Richard Zuniga, Snezana Bosnjak, Sreedevi Daggubati, Daliborka Bursac. ONTARGET: Phase 3 randomized, double-blind, placebo-controlled trial evaluating crofelemer for the prophylaxis of diarrhea in adult patients with solid tumors receiving targeted therapies with or without standard 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 PO3-13-01.

Abstract PO1-05-12: Pooled clinical trial data analyses comparing the biology of HER2-low vs HER2-0 breast cancer in patients with metastatic breast cancer following treatment with standard single agent chemotherapy

Abstract Background: Prior analyses of observational data suggest that for patients with metastatic breast cancer (MBC), tumor biology does not vary by HER2-low vs. HER2-0 expression given similar overall survival (OS) times after accounting for patients’ clinicopathologic features including hormone receptor (HR) status. We sought to evaluate potential differential biology by HER2-low status by (1) studying data pertaining to patients treated in historic clinical trials (i.e., data collected to measure associations between protocol defined treatments and outcomes) and (2) evaluating the endpoint of progression-free survival (PFS) in addition to OS following treatment with standard single agent chemotherapy for MBC. Methods: Pooling anonymized clinical trial data from studies within the Medidata Enterprise Data Store, we identified 142 women with HER2-negative MBC who received treatment with an NCCN recommended single agent chemotherapy in the context of a clinical trial. Using patient-level immunohistochemistry (IHC) results, we categorized patients as either HER2-low (IHC 1+/2+ and not amplified by in situ hybridization) or HER2-0 (IHC 0). We compared patients’ baseline demographic and clinicopathologic features according to HER2-low vs HER2-0 status. We used Cox proportional-hazard models stratified by HR status to estimate OS and PFS according to HER2-low vs HER2-0 classification while adjusting for patients' baseline demographic and clinicopathologic attributes. Results: Patients with HER2-low disease represented 20% (28/142) of the HER2-negative cohort. Twenty-five percent (7/28) of HER2-low patients had tumors that expressed hormone receptors compared with 17% (19/114) of HER2-0 patients (p=0.31). In this cohort, the maximum follow up time was 38.4 months. For HER2-low patients vs HER2-0 patients, the median OS was 10.7 vs. 12.7 months (p=0.37), and the median PFS was 3.5 vs. 2.9 months (log rank test, p=0.53) respectively. In Cox proportional-hazard models that adjusted for patient demographic and clinicopathologic features and were stratified by HR status, patients with HER2-low tumors had an 16% elevated (non-significant) hazard of death compared with patients with HER2-0 tumors (HR 1.16, 95% CI: 0.69-1.95) and a 22% reduced (non-significant) hazard of progression or death (HR 0.78, 95% CI: 0.45-1.35). Conclusions: Analyses of pooled historic clinical trial data pertaining to women with HER2-negative MBC who were treated with single agent chemotherapy revealed no meaningful clinical differences in either OS or PFS endpoints according to HER2-negative subtypes (i.e., HER2-low vs. HER2-0) after accounting for patient demographic and clinicopathologic features. These results support prior findings from observational research suggesting that there are no biological differences associated with HER2-negative subtypes. Table. Multivariable Cox Proportional Hazards Models for OS and PFS Stratified by Hormone Receptor Status, (N=134) Variable OS PFS HR* 95% CI HR* 95% CI Age (decade) 0.84 0.70-1.01 0.86 0.72-1.01 Race White 1.00 (referent) 1.00 (referent) Black 1.75 0.84-3.63 1.57 0.66-3.73 Asian 0.93 0.47-1.80 1.33 0.71-2.51 Other 1.69 0.45-6.38 2.10 0.62-7.15 Ethnicity Non-Hispanic or Latino 1.00 (referent) 1.00 (referent) Hispanic or Latino 2.10 0.95-4.64 1.02 0.44-2.35 HER2 Characterization HER2-0 1.00 (referent) 1.00 (referent) HER2-1+/2+ 1.16 0.69-1.95 0.78 0.45-1.35 Prior Lines of Chemotherapy for Metastatic Disease 0 1.00 (referent) 1.00 (referent) 1 0.82 0.46-1.46 1.13 0.65-1.95 2 0.69 0.35-1.36 1.00 0.52-1.93 3 0.59 0.10-3.42 2.18 0.45-10.50 ECOG Performance Status 0 1.00 (referent) 1.00 (referent) 1 1.65 1.07-2.54 1.57 1.02-2.43 Legend: OS=overall survival; PFS=progression-free survival; HR=hazard ratio; HER2=human epidermal group factor receptor 2; ECOG=Eastern Cooperative Oncology Group. *Analyses adjusted for clinical trial membership (coefficients not reported) Citation Format: Elizabeth Lamont, Emily Stein, Paolo Tarantino, Sara Tolaney, Corinne Ahlberg, Krishna Chinnathambu, Jiezhi Qi, Kala Tummagunta, Jackie Bilan, Ruthanna Davi, Lisa Ensign. Pooled clinical trial data analyses comparing the biology of HER2-low vs HER2-0 breast cancer in patients with metastatic breast cancer following treatment with standard single agent 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 PO1-05-12.

Abstract PO5-21-06: Pathway profiling for prediction of response to neoadjuvant Letrozole therapy in ER positive postmenopausal breast cancer: gaining new insights for targeted treatment

Abstract Introduction: The NEOLBC (NCT03283384) study included postmenopausal patients with hormone receptor positive (ER≥50%, PR any), HER2 negative, stage II/III breast cancer. A baseline biopsy was taken prior to start letrozole treatment and after two weeks of treatment. Based on the two week Ki67-IHC, patients were randomized (Ki67 ≥1%) to receive either Letrozole + Ribociclib or standard chemotherapy until surgery, or continued (Ki67 &amp;lt; 1%) Letrozole mono therapy. Here we describe the signal transduction pathway profiles to better understand the molecular mechanisms of response to neoadjuvant letrozole. Methods: Signal transduction pathway activities for the ER, AR, MAPK, PI3K, HH, TGFβ and Notch pathways were measured on baseline and two weeks samples using the OncoSIGNal qPCR test (InnoSIGN). High pathway activity in a tumor sample was defined as pathway activity value above the 95th percentile of reference normal epithelial breast tissue. The pathway activity patterns of the Ki67 &amp;lt; 1% (n=30) and Ki67 &amp;gt; 1% (n=63) groups were compared between baseline and two weeks of treatment. Results: Although all measured baseline samples (n=93) were ER IHC staining positive (≥50%), there is a large range in baseline ER signal transduction pathway activity (32 to 78 on a scale from 0 – 100) and 20% of the samples show an ER-activity range (32 - 45) that normally falls in the range of ER IHC stained negative breast tissue. The group with Ki67 &amp;gt; 1% after 2 weeks Letrozole treatment showed non elevated ER pathway activity at baseline more often (25%) compared to the Ki67 &amp;lt; 1% group (10%). 92% of the patients showed a decrease in ER pathway (11.6 ± 8.6) activity after 2 week letrozole treatment compared to baseline (p=8.5e-13). Interestingly, baseline AR pathway activity has a good differentiating predictive value for the two week response to letrozole treatment and the overall AR pathway activity score was higher in the low Ki67 group (51.4 ± 7.4) than in the Ki67 ≥ 1% group (46.7 ± 6.4; p=0.0053) and more often classified as high in 30% of the low Ki67 group vs. 13% of the Ki67 ≥ 1% group. The Ki67 &amp;gt; 1% group showed activation of non-hormonal pathways (PI3K, MAPK and/or HH) more frequent (38%) at baseline compared to the &amp;lt; 1% Ki67 group (19%). Conclusion: Positive ER staining does not always relate to a high ER pathway activity, possibly explaining that not all patients respond equally well to ER inhibition therapy. Activation of hormonal pathways (ER, but also AR) appear to be predictive for early (2 weeks) response towards Letrozole as assessed by Ki67 staining. Involvement of non-hormonal pathways is associated with less effective response towards Letrozole alone. Pathway activity patterns could improve insight to underlying hormonal treatment escape mechanisms which could lead to alternative treatment options in patients with ER-positive breast cancer. Citation Format: Nadia de Gruil, Anne Florine de Groot, Yvonne Wesseling-Rozendaal, Diederick Keizer, Sigi Neerken, Judith Kroep. Pathway profiling for prediction of response to neoadjuvant Letrozole therapy in ER positive postmenopausal breast cancer: gaining new insights for targeted 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 PO5-21-06.

Abstract PO2-01-05: Neoadjuvant pyrotinib plus trastuzumab, and chemoterapy in patients with HER2-positive early breast cancer: a real-world study

Abstract Background Pyrotinib is a new oral, irreversible pan-ErbB receptor tyrosine kinase inhibitor that targets human epidermal growth factor receptor 1 (HER1), HER2, and HER4. Previous studies have confirmed it combined with capecitabine is safe and well-tolerated in advanced breast cancer. And also PHEDRA trial had demonstrated the efficacy and safety of pyrotinib combined with trastuzumab and docetaxel neoadjuvant therapy early HER2-positive breast cancer. However, the efficacy of pyrotinib plus trastuzumab-based in real-world neoadjuvant therapy for early breast cancer is unknown. Purpose The present study aimed to explore the efficacy of pyrotinib-based in neoadjuvant therapy for early breast cancer in real-world. Method This is investigator-initiated phase 2 real-world study recruited eligible patients, aged 18–70 years with invasive carcinoma, cT2-3N0-3M0 stage, HER2-positive breast cancer. The patients received 400 mg pyrotinib orally once per day for 21 days and trastuzumab (8 mg/kg loading dose, 6 mg/kg maintenance dose) plus different standard chemotherapy, including six 21-day cycles of docetaxel (75 mg/m2) plus carboplatin (6 mg/mL/min), or four cycles of epirubicin (90 mg/m2) plus cyclophosphamide (600 mg/m2) and four cycles paclitaxel (80 mg/m2). The primary endpoint was to calculate the number of patients who achieved a pathological complete response (pCR, ypT0/is, ypN0). (ChiCTR2100052892). Result The results of the 23 patients were reported, The pCR of 12 (52.2%) patients, who reached the threshold for the design, was noted. The study is ongoing. The most frequent grade 3 to 4 adverse events were diarrhea (35.6%), which all the patients received primary prevention of diarrhea, leukopenia (44.8%), and anaemia (23.7%). However, no treatment-related deaths were recorded. Conclusion Previous studies have shown the efficacy and safety of pyrotinib plus trastuzumab and docetaxel in neoadjuvant therapy of HER2-positive early breast cancer. The current trial suggests that pyrotinib plus trastuzumab-based standard chemotherapy in real-world has promising efficacy and manageable toxicity in patients with HER2-positive early breast cancer in a neoadjuvant setting, the trial is ongoing, we will enroll more patients. Citation Format: Jun Zhou, Rui Wang. Neoadjuvant pyrotinib plus trastuzumab, and chemoterapy in patients with HER2-positive early breast cancer: a real-world study [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 PO2-01-05.

Abstract PO2-06-04: Prospective study on eribulin efficacy in advanced and metastatic breast cancer: changes in TGF-β compared to other standard chemotherapy agents (KBCSG-TR 2018, POTENTIAL)

Abstract Introduction Eribulin (E) has been demonstrated to improve overall survival (OS) compared to standard chemotherapies in pivotal phase III clinical trials (studies 301 and 305), although there was no difference in progression-free survival. These findings suggest that E might have a mechanism for OS improvement different from the common anti-tumor effect. Several studies reported that E inhibits epithelial-mesenchymal transition and the suppression of TGF-β plays a central role. Data on the relationship between the E-induced serial change in TGF-β and the improvement in OS remains insufficient. Therefore, we conducted this prospective observational study of patients treated with E while undergoing sequential TGF-β testing. This study also enrolled patients who received chemotherapy other than E as a control. Methods Patients with HER2-negative recurrent/metastatic breast cancer (MBC) were prospectively enrolled from 23 breast cancer centers in Japan, if they had not previously used E, had received two or fewer prior chemotherapy regimens, and were scheduled to start either E, capecitabine, S-1 or paclitaxel (± bevacizumab) between September 2020 and February 2022. The target sample sizes were 150 and 50 patients scheduled to receive E (Cohort E) and other drugs (Cohort Others), respectively. We collected blood samples for TGF-β testing at baseline, at two or three weeks (week 2/3), and at four or five weeks (week 4/5) from the beginning. The observation period was until February 2023. The primary endpoint was to evaluate the relationship between changes in TGF-β and clinical response, including OS and time to treatment failure (TTF). Results A total of 202 of the 203 enrolled patients were included in the analysis (1 patient declined consent). The median age was 60.0 (interquartile range, 52.0-69.0) years and ECOG performance status was 0 or 1 in all patients. Among 152 patients in Cohort E and 50 patients in Cohort Others, 37 patients (24.3%) and 12 patients (24.0%) had hormonal receptor-negative breast cancer, and 29 patients (19.1%) and 30 patients (60.0%) had no prior chemotherapy for MBC, respectively. Visceral metastasis totaled 115 (75.7%) in Cohort E and 46 (92.0%) in Cohort Others. In OS analysis of 199 patients, the median OS was 24.5 months (95% CI, 17.3-NA) for no prior chemotherapy, and 17.7 months for one or two prior chemotherapy (median follow-up 14.5 months). In Cohort E and Cohort Others, 139 and 45 patients, respectively, had paired samples for TGF-β testing at baseline and week 2/3. The proportion of patients with a percent change at week 2/3 from baseline in TGF-β (ΔTGF-β) of less than zero (decreased TGF-β) was 46.8% in Cohort E and 33.3% in Cohort Others, indicating a 13.4% (-2.6% – 29.5%) higher trend in Cohort E. Based on the time-dependent receiver operating characteristic (ROC) curves at 6 months for TTF, the threshold of ΔTGF-β was determined to be 27%. For the low ΔTGF-β group (&amp;lt; 27%) and the high ΔTGF-β group (≥27%), OS rates at median follow-up (14.5 months) were 70.6% and 54.3% (p=0.085) in Cohort E and 68.9% and 58.2% (p=0.585) in Cohort Others, respectively, suggesting a relationship between low ΔTGF-β and a favorable prognosis only in Cohort E. Conclusions The current study showed the trend in the higher frequency of decreased TGF-β, as well as the important relationship between decreased TGF-β and a favorable prognosis in patients treated with E compared with those receiving other chemotherapies. As the next step, further biomarker analyses including cytokines and chemokines, and immunological analyses are planned. Citation Format: Takahiro Nakayama, Tersuhiro Yoshinami, Fumie Fujisawa, Minako Nishio, Takashi Yamanaka, Toshinari Yamashita, Chiya Oshiro, Ayaka Izui, Nobumoto Tomioka, Hideki Maeda, Masafumi Shimoda, Kenzo Shimazu, Michiko Tsuneizumi, Ryoichi Matsunuma, Hiroko Bando, Aya Ueda, Hiroyuki Yasojima, Kumiko Okada, Kenichi Inoue, Yuichiro Kai, Katsuhide Yoshidome, Hidetoshi Kawaguchi, Masayuki Nagahashi, Kazuteru Oshima, Shinichiro Kashiwagi, Tsutomu Iwasa, Kanae Taruno, Shigeru Tsuyuki, Fumine Tsukamoto, Takashi Morimoto, Nobuyoshi Kittaka, Toru Higuchi, Yoichi Naito, Ryotaro Saita, Hiroyoshi Nishikawa, Daisuke Sugiyama, Yasuo Miyoshi, Yohei Uchida, Tomomi Yamada, Norikazu Masuda. Prospective study on eribulin efficacy in advanced and metastatic breast cancer: changes in TGF-β compared to other standard chemotherapy agents (KBCSG-TR 2018, POTENTIAL) [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 PO2-06-04.

Abstract PO4-19-08: Randomized phase II study of talazoparib vs talazoparib plus atezolizumab for patients with premenopausal HR+/HER2- metastatic breast cancer harboring homologous recombination deficiency scar (Young-PALETTA, KCSG BR21-09)

Abstract Background Cyclin D kinase-4/6(CDK4/6) inhibitor combined with endocrine treatment have significantly increased progression free survival(PFS) and overall survival(OS) of patients with hormone receptor(HR)-positive/HER2-negative metastatic breast cancer, and currently is a standard 1st line endocrine treatment option. Homologous recombination deficiency(HRD) including germline(g) BRCA1/2 pathogenic mutation is known to be prevalent among young premenopausal patients. Recently several retrospective data suggested that patients with germline BRCA1/2 pathogenic mutation or HRD have poorer outcome with CDK4/6 inhibitor treatment, however there is no prospective evidence. Poly ADP-ribose polymerase(PARP) inhibitors have shown significant benefit over standard chemotherapy in patients with HER2-neg metastatic breast cancer and gBRCA1/2 pathogenic mutation in two Phase 3 trials. Since preclinical data suggested that PARP inhibitors play a role in anti-tumor immune modulation, immunotherapy combined with PARP inhibitors were explored and showed promising antitumor efficacy in several single arm trials. In this trial, we investigate talazoparib and atezolizumab combination compared with talazoparib monotherapy in premenopausal women with HR+/HER2- metastatic breast cancer with HRD-scar after failure with 1st line palbociclib and endocrine treatment combination. Methods This study is a multicenter, randomized, open-label phase II trial comparing talazoparib versus talazoparib with atezolizumab in premenopausal women with HR+/HER2- metastatic breast cancer harboring HRD scar whose disease have progressed with endocrine and palbociclib combination as the 1st-line endocrine treatment. Prior one line of cytotoxic chemotherapy other than platinum for metastatic setting is allowed, but prior palliative endocrine treatment is not allowed. Eligible patients will be pre-screened with tumor tissue biopsy and peripheral blood sampling before endocrine and palbociclib treatment commencement. HRD status is determined through targeted sequencing(SOLIDaccuTestTM by NGeneBio) of tumor tissue and germline HRD genes including BRCA1/2 variant test. Whole genome sequencing and RNA sequencing are performed for biomarker analyses. Patients harboring HRD scar will receive first line endocrine treatment with palbociclib plus aromatase inhibitor with ovarian suppression. After progression with 1L endocrine treatment, patients will be randomized to either talazoparib alone or talazoparib plus atezolizumab combination. Germline BRCA1/2 pathogenic mutation is a stratification factor. Primary endpoint is a progression free survival after randomization(PFS2). Secondary objectives are a composite of PFS1 and PFS2, PFS1, overall survival, patient reported outcome, and biomarkers for treatment response. A total of 178 subjects are required to detect hazard ratio of 0.62 (median PFS2 of at least 10.5 months with talazoparib and atezolizumab combination vs 6.5 months with talazoparib alone), to achieve 80% power at a two-sided a significance level at 10%, considering drop-out rate of 5%. The study period is expected to be 72 months overall(36 months for accrual and randomization and 24 months of follow-up for primary endpoint PFS2). Citation Format: Hee Kyung Ahn, Jieun Lee, Jee Hung Kim, Kyung-Hun Lee, Jee Hyun Kim, Min Hwan Kim, Minsuk Kwon, Han Jo Kim, Kyung Hae Jung, Yeon Hee Park. Randomized phase II study of talazoparib vs talazoparib plus atezolizumab for patients with premenopausal HR+/HER2- metastatic breast cancer harboring homologous recombination deficiency scar (Young-PALETTA, KCSG BR21-09) [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 PO4-19-08.

Abstract PO5-26-01: Assessing the effect of multimodal therapy in massive fungating breast cancers without distant metastasis

Abstract Background: Massive fungating breast cancers (MFBCs), which comprise exudative, foul-smelling tumors, the size of a child’s head or involve extensive ulceration are classified as locally advanced breast cancers. The National Comprehensive Cancer Network guidelines recommend preoperative neoadjuvant chemotherapy in patients with locally advanced breast cancer without distant metastases. However, limited evidence is available regarding the successful treatment of fungating breast cancers. In clinical practice, many fungating breast cancer cases are treated as stage IV tumors. This study aimed to investigate whether multimodal therapy, including surgery for giant breast cancers, can improve survival rates and whether the survival rates are comparable to those of other stage III breast cancers. Subjects and methods: Out of 1480 cases of primary breast cancer diagnosed at our hospital between June 2012 and March 2020, 123 patients with clinical stages IIIA–IIIC were chosen for analysis. Furthermore, 29 of these patients with MFBC were selected. During multimodal therapy for selected patients with fungating breast cancer, difficulties were encountered in some patients with single-stage skin suturing and closure after standard neoadjuvant chemotherapy. These patients underwent surgery with an additional skin flap or skin grafting. Furthermore, radiation therapy was added as needed. We compared the survival rates of these patients with those of patients who received drug therapy only according to the therapeutic protocol for Stage IV. Survival rates of patients with MFBC and other stage III breast cancers were also compared. Statistical analyses were conducted using the Kaplan–Meier curve and the log-rank test. Results: Of the 29 patients with MFBC, 22 (75.9%) and seven (24.1%) were treated with multimodal and palliative therapies, respectively. The median age and follow-up period of the multimodal therapy group were 62 (range: 43–94) years and 67 (range, 32–131) months, respectively. The corresponding values for the palliative therapy group were 79 (range: 42–88) years and 31 (range: 2–96) months. All patients in the palliative treatment group were hormone receptor positive and HER2 negative, and treatment with hormone therapy was initiated. The 7-year survival rate was significantly higher in the multimodal therapy group than in the palliative treatment group (92.3% vs. 68.6%, p = 0.0317). Furthermore, the 5-year distant recurrence-free rate was higher in the multimodal treatment group (79.3% vs. 63.5%). Local recurrence did not occur in any patient in the multimodal treatment group. There was no significant difference in the 7-year survival rates between patients with MFBC and those with other stage III breast cancers (86.8% vs. 75.3%; p = 0.239). Triple-negative breast cancer accounted for 20.8% (20 96) of the other stage III breast cancers, but none of these were MFBCs. Conclusions: Clinically, MFBCs are often palliatively treated as stage IV tumors, even in the absence of distant metastasis. However, the survival rate was significantly higher in the multimodal therapy group than in the palliative treatment group. Furthermore, the survival and distant recurrence-free rates for MFBC were higher than those for other stage III breast cancers. Therefore, patients with MFBCs should be actively treated using curative treatments. Citation Format: Tamaki Tamanuki, Maki Namura, Tomoyoshi Aoyagi, Haruhito Sakata, Mika Iwai, Shinichirou Shimizu, Hiroshi Matsuzaki. Assessing the effect of multimodal therapy in massive fungating breast cancers without distant metastasis [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 PO5-26-01.

Abstract PO4-03-13: High B7-H3 expression with low PD-L1 expression identifies armored-cold tumors suggesting potential anti-B7-H3 therapy in triple-negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) is generally regarded as the most aggressive subtype among breast cancer. B7 homolog 3 protein (B7-H3), also known as CD276, is an emerging immune checkpoint molecule, which plays a dual role in the immune system. Multiple anti-B7-H3 therapies has been raised, such as DS-7300, MGA271, MGD009, and B7-H3 chimeric antigen receptor T-cell immunotherapy (CAR-T). However, the expression of B7-H3 in TNBC and its value as a biomarker identifying therapeutic options has not been elucidated Methods: A total of 165 samples (83 non-TNBC and 82 TNBC) were included in this study, and 6 samples included paired para-tumor samples. In addition, 30 TNBC patients receiving standardized neoadjuvant chemotherapy (NAT) were recruited. After 8 cycles of NAT, the response to NAT was assessed by RECIST1.1 criterion before surgical operation. Moreover, multiple public cohorts of breast cancer and TNBC were obtained, including the TCGA dataset, the METABRIC dataset, the GSE176307 (durvalumab-based therapy) dataset, the PRJNA558949 (durvalumab-based therapy) dataset, the GSE194040 (paclitaxel-based therapy) dataset, and the GSE34138 (anthracycline-based therapy) dataset. Based on multiple in-house and public cohorts, we investigated the expression features of B7-H3 in breast cancer and checked the anti-tumor effect of the B7-H3 monoclonal antibody in mouse model. We also developed a novel classifier combined B7-H3 and PD-L1 expression in TNBC. Results: B7-H3 was highly expressed in tumor tissues in the in-house and the TCGA cohorts. B7-H3 expression did not differ significantly between non-TNBC and TNBC samples in the in-house and the TCGA cohorts, excepting for the METABIRC cohort. There was no notable difference in CD8+ cells infiltration between B7-H3 low and high expressed non-TNBC samples, but CD8+ cells was notably higher in the B7-H3 low expressed TNBC samples. The similar findings were also observed in the TCGA and the METABIRC cohorts. In addition, enrichment analysis of transcriptome data and analysis of in-house samples showed that B7-H3 was positively related to most collagens. Moreover, anti-B7-H3 therapy significantly inhibited tumor growth in mouse TNBC model, notably increased immune cells infiltration, and also reduced collagen deposition within the tumor. Given the notable value of PD-L1 in predicting immunotherapy responses, we also combined B7-H3 and PD-L1 expression to establish a novel subtyping strategy. TNBC patients with B7-H3highPDL1low feature exhibited the lowest anti-tumor immune infiltration and higher collagen deposition level. In the durvalumab-dependent cohort, paclitaxel-dependent cohort, anthracycline-dependent cohort, and our recruited NAT cohort, the B7-H3highPDL1low subgroup exhibited the lowest therapeutic response. Conclusions: Overall, this research provides a novel subtyping strategy based on the combination of B7-H3/PD-L1 expression that could potentially be applied to predict the therapeutic responses in TNBC, and suggests a potential biomarker-guided anti-B7-H3 therapy. Based on the classifier, we can select potential beneficiaries to deliver personalized medical services. Citation Format: Jie Mei, Yun Cai, Ziyi Fu, Yongmei Yin. High B7-H3 expression with low PD-L1 expression identifies armored-cold tumors suggesting potential anti-B7-H3 therapy in 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 PO4-03-13.

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&amp;lt; 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&amp;lt; 0.001). Cohorts A/A2 experienced an absolute sTIL increase of 7.4% (P&amp;lt; 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&amp;lt; 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.