Standard Chemotherapy Research Articles

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 < 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 < 1% (n=30) and Ki67 > 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 > 1% after 2 weeks Letrozole treatment showed non elevated ER pathway activity at baseline more often (25%) compared to the Ki67 < 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 > 1% group showed activation of non-hormonal pathways (PI3K, MAPK and/or HH) more frequent (38%) at baseline compared to the < 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 (< 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< 0.01) in monocytic MDSCs compared to baseline; decrease in granulocytic MDSCs was not statistically significant. 37 patients had paired biopsies adequate for sTIL evaluation with a mean change from 23.4% to 30.3% (absolute change 6.9%, P< 0.001). Cohorts A/A2 experienced an absolute sTIL increase of 7.4% (P< 0.01); Cohort B experienced absolute sTIL increase of 6.1% (P=0.01). PD-L1 expression in tumors (H-score using MoAb 22C3 clone) increased by 43% (P< 0.01) across all cohorts. 16 of the 39 patients (41.0%) who proceeded to resection achieved pCR (n=12 of 27 [44.4%] in Cohorts A/A2 and n=4 of 13 [30.8%] in Cohort B). The most frequently reported irAEs were adrenal insufficiency (n=5, 10.9%), maculopapular rash (n=3, 6.5%), and hypothyroidism (n=3, 6.5%). Conclusions: Treatment in the pre-neoadjuvant window with decitabine and pembro could potentially sensitize breast cancers to standard NCT by recruitment of TILs to the tumor tissue. The treatment was well -tolerated at the tested doses. Funding: financial support and drug (pembrolizumab) were provided by Merck Citation Format: Harry Bear, Xiaoyan Deng, Dipankar Bandyopadhyay, Michael Idowu, Maciej Kmieciak, Monique Williams, Giovanni Archer, Lindsey Gwaltney, Patrick Dillon, Daniel Flora, Daniel Stover, Andrew Poklepovic, Mary Hackney, Masey Ross, Hetal Vachhani, Raphael Louie, Kandace McGuire, Amelia Grover, Tasnim Rahman, Amber Hendrix. Neoadjuvant pembrolizumab + decitabine followed by standard neoadjuvant chemotherapy for locally advanced HER2- breast cancer (NCT02957968) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-18-04.

Abstract PS09-09: Multiomics profiling and molecular classification refine precision treatment strategies for HER2-positive breast cancer

Abstract Background: Anti-HER2 targeted therapy has achieved a series of breakthroughs. However, the current treatment strategy regarding HER2-positive breast cancer remains indiscriminate and lacks specificity, which limits the further improvement of overall treatment response and may lead to overtreatment and extra cost for some patients. Our study aims to reveal the molecular heterogeneity of HER2-positive breast cancer to guide a more precise treatment. Patients and methods: We selected HER2-positive breast cancer patients treated at Fudan University Shanghai Cancer Center between 2013 and 2014 and conducted genomic, transcriptomic, proteomic and metabolomic profiling. We then applied a non-negative matrix factorization algorithm on transcriptomic data to obtain an unsupervised classification. And we further studied the correlation between subtypes and corresponding treatment strategies in multiple cohorts of adjuvant and neoadjuvant therapy. For clinical accessibility, we developed convolutional neural network models through deep learning algorithm based on digital pathology to identify different subtypes. Additionally, we explored novel treatment strategies using the patient-derived organoids (PDOs) models. Results: We established a novel multiomics cohort of 180 HER2- breast cancer patients and classified them into four clinically significant molecular subtypes: (1) A classical HER2-enriched (HER2-CLA, N=51) subtype characterized by strong ERBB2 signaling and remarkable sensitivity to anti-HER2-targeted therapy (pathologic complete response with dual-targeted therapy: 93%). (2) an immunomodulatory (HER2-IM, N=36) subtype characterized by an immune-activated microenvironment and excellent prognosis with current treatment (no relapse in 97% of patients with a median follow-up of 86 months). Tumors of this subtype were therefore candidates for de-escalatory treatment. (3) A luminal-like (HER2-LUM, N=55) subtype distinguished by activated estrogen receptor signaling and (4) a basal/mesenchymal-like (HER2-BM, N=38) subtype enriched in activated receptor tyrosine kinase pathways. HER2-LUM and HER2- BM showed limited benefit from anti-HER2 therapy, and thus, add-on therapies might be needed. The overall area under the curve (AUC) of the convolutional neural network model based on digital pathology for identifying different subtypes is 0.77. In the exploration of novel treatment strategies, we found in the PDO model that the HER2-LUM subtype is more sensitive to a treatment regimen combining standard (chemotherapy and targeted therapy) with subsequent endocrine therapy and CDK4/6 inhibitors compared to other subtypes. Additionally, the HER2-BM subtype demonstrated greater sensitivity to treatment with a combination of EGFR inhibitors, PDGFR inhibitors or VEGFR inhibitors. Conclusion: We uncovered a high degree of molecular heterogeneity in HER2-positive breast cancer and illustrated its impact on treatment response. More precise treatment can be given according to the characteristics of different subtypes, which may achieve good efficacy and simultaneously reduce overtreatment and extra cost. The comprehensive profiling of HER2-positive breast cancers could also serve as an important resource for further exploration. Key Words: HER2-positive breast cancer cohort; molecular classification; targeted therapy; precision treatment; de-escalatory treatment. Citation Format: Yu-Wei Li, Ding Ma, Xiang-Rong Wu, Lei-Jie Dai, Shen Zhao, Yu-Zheng Xu, Xi Jin, Xiao Yi, Ying Wang, Cai-Jin Lin, Yi-Fan Zhou, Tong Fu, Wen-Tao Yang, Ming Li, Hong Lv, Yi-Zhou Jiang, Zhi-Ming Shao. Multiomics profiling and molecular classification refine precision treatment strategies for HER2-positive 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 PS09-09.

Abstract PO5-13-07: Prediction of recurrence in triple negative breast cancer patients after receiving neoadjuvanttreatment using plasma metabolomics

Abstract Background Early-stage triple-negative breast cancer (TNBC) is usually treated with neoadjuvant chemotherapy (NADC), but prognosis remains poor compared with other BC subtypes. Unfortunately, less than 30% of BC patients achieve pathological complete response (pCR) to NADC and the overall survival of TNBC when cancer spreads is estimated at 10-13 months. Complete response is associated with improved progression-free and overall survival rates, but more accurate prognostic markers are needed. In this study, we assessed the prognostic value of blood circulating metabolites by using targeted-based metabolomics. Methods Patients received standard neoadjuvant chemotherapy with epirubicin plus cyclophosphamide followed by paclitaxel. Blood samples were obtained upon completion of chemotherapy and before surgery. Pathological response to treatment was recorded according to the Miller & Payne system, and categorized as partial (MP 1, 2, & 3) or complete response (MP 4 & 5). Blood samples were collected in EDTA tubes, centrifuged and plasma was stored at -80°C. After QC standard addition and methanol extraction of proteins, four fractions of the resulting extract were analysed: two by reverse-phase/UPLC-MS/MS methods with positive ion mode electrospray ionization (ESI), one by reverse phase/UPLC-MS/MS with negative ion mode ESI, and one by hydrophilic interaction liquid chromatography/UPLC-MS/MS) by Metabolon using a Thermo Scientific Q-Exactive mass spectrometer with a heated electrospray ionization source and an Orbitrap mass analyser. Using Metabolon's hardware and software, raw data were extracted, identified, QC processed and quantified using the area under the curve (AUC). Identified compounds were compared with library entries of purified standards or recurrent unknown entities. The prognostic capacity of each metabolite was assessed using BRB ArrayTools. Selected metabolites were validated using a targeted approach using compound standards as follows. Plasma samples were re-analysed by UPLC/MS using a Vanquish LC coupled to an Orbitrap Exploris 240 MS (Thermo Fisher Scientific) with positive and negative ionization mode ESI under polarity switching. Identification of compounds were performed by comparison of retention times (against in-house authentic standards), accurate mass (with an accepted deviation of 3ppm), and MS/MS spectra. These analyses were carried out by MS-Omics (Denmark). Results Twenty patients treated in the Medical Oncology Unit of the University Hospital of Jaén were recruited. Median age was 50 (31-76). Twelve patients obtained a pathological complete response. Median follow-up after surgery was 25 months. Seven patients eventually had distant metastases (2 in the lungs, 1 in the brain, 1 in the bones and 3 multi-site). Metabolon untargeted analysis identified and quantified 985 metabolites, 789 after xenobiotics exclusion. Survival analysis identified 16 metabolites related with distant relapse (p< 0.05). The ten metabolites with lower p-value were selected for targeted validation. Ms-Omics pipeline allowed absolute quantification of 5 metabolites, 3 of them showing high correlation (R >0.7) between both measurements (targeted and untargeted). Validation of the prognostic value of the candidate metabolites is ongoing in a larger TNBC cohort. Conclusions Metabolomics is a useful tool for the detection of simply assessable and cost-effective prognostic biomarkers in TNBC. Easily monitoring the presence of minimal residual disease is worth to be settled up in the clinical practice for the most aggressive molecular subtype of breast cancer. In this work we have defined a set of metabolites that could predict distant relapse events in TNBC patients treated with neoadjuvant chemotherapy. Further analyses are being carried out to validate the prognostic value of the proposed candidate metabolites. Citation Format: Pedro Sánchez-Rovira, Rocio Urbano-Cubero, Angelo Gamez Pozo, Carmen González-Olmedo, Alicia Cano-Jimenez, Andrea Zapater- Moros, Leticia Díaz-Beltrán, Lucia Trilla-Fuertes, Mariana Díaz-Almirón, Enrique Espinosa, Pilar Zamora, Juan Angel Fresno Vara. Prediction of recurrence in triple negative breast cancer patients after receiving neoadjuvanttreatment using plasma metabolomics [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-13-07.

Abstract PO5-16-07: Unveiling the Landscape of PD-L1 Expression and Tumor-Infiltrating Lymphocyte Subtypes in Advanced Triple-Negative Breast Cancer

Abstract Background: Triple-negative breast cancer (TNBC) is known for its aggressive behavior with poor survival outcomes. Influenced by different expression levels of Programmed Death-Ligand 1 (PD-L1) and several subtypes of tumor-infiltrating lymphocytes (TILs), tumor microenvironment (TME) plays a crucial role in TNBC response to treatment and progression. Objective: To assess the prevalence and prognostic role of PD-L1 expression in advanced TNBC, defined as unresectable stage III or stage IV disease, in patients treated with a standard cytotoxic chemotherapy regimen. TILs composition was also evaluated as an exploratory objective. Methods: The internal database of the Brazilian National Cancer Institute was queried out for women diagnosed and treated with advanced TNBC from January 2018 to December 2022. Formalin-fixed paraffin-embedded samples of a maximum of four years old were analyzed. PD-L1 expression using 22C3 pharmDX assay was estimated through combined positive score (CPS) dichotomization (CPS < 10 vs. CPS≥10). Tissue microarrays comprising the samples of biopsies were subjected to immunohistochemistry, targeting specific markers including CD3, CD4, CD8, CD56, CD68, CD117, FOXP3, PD-1, the immune cell profiles were carefully examined and their correlation with the PD-L1 CPS was determined. Results: A total of 150 patients were included. The expression of PD-L1 was undetermined in 2 cases. The median age was 51.5 years (IQR 41.8-60.2) and 20.9% of the cases had CPS≥10. Most patients were < 65 years (73.0%), were postmenopausal (56.8%) and belonged to non-white ethnicity (70.3%). Postmenopausal women predominated in the CPS≥10 subgroup (74.2%) (Table 1). No significant differences in demographic characteristics and clinicopathological variables were observed based on PD-L1 subgroups, 117 patients (79.1%) had CPS < 10, with 91 (77.8%) being de novo stage IV metastatic disease. CD3+ (p=0.037), CD4+ (p=0.005) and CD8+ (p=0.001) TILs had higher expression in tumors with PD-L1 CPS≥10 (Table 2). According to the treatment received, almost half of the patients only received first-line chemotherapy (47%), as the following second line was applied to 28.8% of the total group. The third and fourth lines were administered in 12.9% and 9.1% of patients, respectively. Only 2 patients went through five palliative chemotherapy lines, and only one received up to 6 treatment lines. Between the subgroups CPS≥10 versus CPS < 10 no statistically significant differences were observed in the median progression-free survival (PFS) (5.1 vs. 5.0 months, p=0.89) and overall survival (OS) (8.7 vs. 8.8 months, p=0.6). Conclusion: This study offers insights into the expression patterns of PD-L1 and TILs subtypes in advanced TNBC cases in Brazil. PD-L1 CPS did not influence survival outcomes for this cohort of patients treated with cytotoxic chemotherapy only. The composition of TILs subtypes within the TME appears to vary based on PD-L1 CPS. Table 1. Advanced TNBC population characteristic by CPS (Nf148). Table 2. Tumor Infiltrating Lymphocytes characterization (CD3, CD4, CD8, CD56, CD68, CD 117, FOXP3 and PD-1) and its correlation with CPS status. Citation Format: Alexssandra Lima Siqueira dos Santos, Jesse Lopes da Silva, Lucas Zanetti de Albuquerque, Antônio Lucas Araújo Neto, Cecília Ferreira da Silva, Luana Aguiar Mesquita Cerva, Isabele Ávila Small, Cicera Pimenta Marcelino, Paula de Mendonça Batista, Maria Aparecida do Carmo Rego, Maria Amélia Carlos Souto Maior Borba, Andreia Cristina de Melo. Unveiling the Landscape of PD-L1 Expression and Tumor-Infiltrating Lymphocyte Subtypes in Advanced Triple-Negative Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-16-07.

Abstract RF01-06: Efficacy and safety of toripalimab plus metronomic chemotherapy in HER2 negative metastatic breast cancer: a multicenter phase II trial based on a Bayesian adaptive randomized design

Abstract Background: Combining Immune checkpoint blockade (ICB) with chemotherapy may significantly improve efficacy in patients with breast cancer. Metronomic chemotherapy is based on more frequent and low-dose drug administrations compared with conventional chemotherapy. Some clinical studies with small samples have tried the combination of metronomic chemotherapy and ICB in patients with advanced tumors. However, whether metronomic chemotherapy is more suitable for ICB than conventional chemotherapy is still unclear. Thus, we performed the first clinical trial, to our knowledge, of metronomic chemotherapy combined with PD-1 blockade comparing with the efficacy of combined conventional chemotherapy and ICB. Methods: This study is a multicenter randomized phase 2 trial using a multi-arm design with Bayesian adaptive randomization and efficacy monitoring. Eligible patients have advanced HER2 negative breast cancer, with no more than one prior line of standard chemotherapy. Patients were randomized to 5 groups: ① metronomic vinorelbine (NVB, 40 mg/day, TIW) monotherapy (the control cohort); ② NVB + Toripalimab (anti-PD1 antibody, 240 mg Q3W); ③Bevacizumab (5 mg/kg Q3W) + NVB+ Toripalimab (the BEV cohort); ④ Cisplatin (50mg/m Q3W) + NVB + Toripalimab (the DDP cohort), ⑤Cyclophosphamide (50mg/day, QD) + Capecitabine (500 mg, TID) + NVB+ Toripalimab (the VEX cohort). The primary endpoint is disease control rate (DCR), and secondary endpoints are objective response rate (ORR), progression free survival (PFS), and overall survival (OS). The safety profile has also been assessed. Mass cytometry time-of-flight (CyTOF) analyses of paired blood samples were performed to demonstrate dynamic changes in systemic immune profile. Results: A total of 103 patients were randomized. Characteristics were as expected for advanced breast cancer and balanced between cohorts. Adverse events of any grade occurred in 64 patients, with 5.2% grade >3. The rate of nausea was significantly higher in the cisplatin cohort than in the others (P< 0.001). Toripalimab was not associated with any previously unreported toxicity. Among the five treatment cohorts, the VEX cohort and the cisplatin cohort had the highest DCR, 69.7% (95% CI 51.7–85.9%) and 73.7% (95% CI 56.1–88.7%), respectively. Followed by the bevacizumab cohort, DCR is 55.7% (95% CI 37.4%–73.6%). Most objective responses were observed in the VEX cohort (ORR: 18.5%; 95% CI 5.6–34.1%), followed by cisplatin (ORR 14.5%; 95% CI 3.3–29.0%). It is worth noting that the PFS of patients in the VEX cohort was the longest, reaching 6.6 months (95% CI 4.0-5.9), followed by 4.0 months (95% CI 2.4-10.4) in patients of the bevacizumab cohort. The PFS of patients receiving the cisplatin regimen was relatively short, only 3.5 months (95% CI 2.2-5.3). Similarly, patients in the cisplatin cohort had shorter OS than those in the VEX and bevacizumab cohorts. In the TNBC subgroup, again, patients in the VEX cohort had the highest DCR (74.1%, 95%CI 47.9%-95.4%) and longest PFS (9.8 months, 95%CI 3.8-21.9). We obtained over 63 million cells in total and clustered CD45+ immune cells into 32 clusters. The systemic immune profile of patients changed dramatically over 2 cycles of PD-1 blockade. However, only the change of cluster 30 differed between responders and non-responders. This is a group of intermediate monocytes with a high expression of CD38, which decreased in responders but significantly increased in non-responders. CD38-NAD+ axis regulates the PD1+ exhausted T cell function. Meanwhile, the overall expression of CD38 in monocytes was significantly increased by DDP and BEV treatment compared with baseline, but not in the VEX groups. DDP significantly increased the expression level of CD38 on NK cells, while BEV or VEX treatment did not affect it. Conclusions: These data suggest promising clinical efficacy and evidence of cooperativity between metronomic VEX chemotherapy and PD-1 blockade. Citation Format: Hongnan Mo, Xiaoying Sun, Jingtong Zhai, Jiashu Han, Hewei Ge, Yuhan Wei, Xiuwen Guan, Haili Qian, Fei Ma. Efficacy and safety of toripalimab plus metronomic chemotherapy in HER2 negative metastatic breast cancer: a multicenter phase II trial based on a Bayesian adaptive randomized design [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 RF01-06.

Abstract PO2-05-14: Prognosis and clinicopathological characteristics of HER2-negative metastatic breast cancers with low expression of hormone receptors: real world evidence from the French ESME cohort

Abstract Background: HER2-negative breast cancers expressing low (1-9 %) immunohistochemistry levels of hormone receptors (HR, estrogen and progesterone receptors), remain an uncertain category, being considered either as triple negative breast cancers (TNBC) or HR-positive (HR+) tumors across guidelines or approvals. The issues regarding this clinical subgroup are both prognostic, with the need of a better definition of their clinical outcome, as well as predictive. Methods: The ESME database is a French National cohort of all consecutive patients who initiated a first-line treatment for metastatic breast cancer (MBC) from 2008 on, in one of the 18 French Comprehensive Cancer Centers. Patients with HER2-negative (0 to 2+, ISH negative) MBC and known estrogen receptor (ER) and progesterone receptors (PR) expression levels were selected. Primary objective was to evaluate crude overall survival (OS) in HER2-/HR-low (ER and PR 0-9 and not TNBC) MBC pts compared with those with TNBC and HR+ disease defined by ER and PR < 1%, and ER ± PR ≥ 10%, respectively. In these 3 populations, predefined secondary objectives were to evaluate PFS under first line chemotherapy (CT), to describe clinical characteristics and the distribution of genetic abnormalities identified at the time of MBC diagnosis. Results: Out of 30,459 patients in the ESME database initiating their MBC treatment between 01/2008 and 01/2021, 19109 patients (2113 TNBC; 228 HR-low; 16768 HR+) were eligible for this analysis. Median follow-up was 58.0 months (95%CI [56.6; 59.0]). Median OS were 15.7 months [15.0-16.8], 19.1 months [15.5-22.4] and 44.6 months [43.8-45.5] in the TNBC, HR-low and HR+ subgroups, respectively. The multivariable analysis adjusted on age at MBC diagnosis, pathological grade and subtype, metastatic-free interval, number and sites of metastases and HER2 status (0 vs. 1-2+), identified no significant OS difference between HR-low and TNBC subgroups (HR=0.95, 95%CI 0.79-1.14), while HR+ patients had a better OS than TNBC patients (reference) (HR=0.50, 95%CI 0.47-0.53). Of these 19109 pts, 8910 received first-line CT regimen (1960 TNBC; 195 HR-low; 6755 HR+): taxanes-based: 66.7%, anthracyclines-based: 32.9%, capecitabine: 18%. Median PFS under first line CT were 5.3 (5.1-5.6), 5.1 (4.1-6.2) and 10.2 months (9.9-10.6) for TNBC, HR-low and HR+ subgroups, respectively. In the multivariable analysis adjusted on the same variables, the HR-low subgroup had a statistically poorer PFS compared to TNBC (HR=1.24, 95% CI 1.04-1.49). On the other hand, the HR+ subgroup had a better PFS than the TNBC (HR=0.74, 95%CI [0.70; 0.78]). Baseline germline BRCA1 mutations (at MBC diagnosis) were present in 4.5% of the TNBC cases, 2.6% of the HR-low cases, and 0.4% of the HR+ cases. The distribution of germline BRCA2 mutations was more homogeneous between the three groups (0.9% of TNBC cases, 1.3% of HR-low cases and 1.1 % of HR+ cases). Conclusions: In this large cohort, patients with HER2-negative, HR-low MBC seem to share similar general prognosis, oncogenetic features and PFS under standard chemotherapy treatment with TNBC patients. Citation Format: Marie Alexandre, Ludovic Gauthier, Audrey Mailliez, Thibault DE LA MOTTE ROUGE, Thomas Bachelot, Monica Arnedos, Florence Dalenc, Etienne Brain, Jean-Marc Ferrero, Vincent Massard, Isabelle Desmoulins, Marie-Ange Mouret-Reynier, Christelle Levy, Anthony Gonçalves, Marianne Leheurteur, Thierry Petit, Jean-Sébastien Frenel, Lise Bosquet, Suzette Delaloge, William Jacot. Prognosis and clinicopathological characteristics of HER2-negative metastatic breast cancers with low expression of hormone receptors: real world evidence from the French ESME cohort [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 PO2-05-14.

Abstract PO3-18-10: Impact of age and ovarian function suppression (OFS) on endocrine response to short preoperative endocrine therapy (ET): Results from the multicenter WSG-ADAPTcycle trial (n=5,290)

Abstract Background In HR+/HER2- early breast cancer (EBC), short preoperative endocrine therapy (ET) offers a promising tool for assessment of ET-efficacy based on Ki67-decrease after 2-4 weeks of treatment. Low post-endocrine Ki67 (Ki67post) is associated with good prognosis in several large prospective trials. WSG-ADAPT demonstrated that Ki67post is a promising tool for decision making in cases with uncertain adjuvant chemotherapy indication, e.g., in premenopausal patients (pts.) with N0 and Recurrence Score (RS, Oncotype DX®) RS 16-25 or N1 and RS ≤25. Preliminary results from the phase III ADAPTcycle trial indicated higher efficacy of preoperative ET in premenopausal pts. if ovarian function suppression (OFS) was used together with tamoxifen (TAM) or aromatase inhibitors (AI). In the ADAPTcycle screening population, we are now able to validate these results and investigate the influence of age subgroups, Recurrence Score, and individual biological markers, as well as OFS on ET-response. Methods In ADAPTcycle (n=5,290 screened until 06/23 at 84 sites in Germany), N0-1 pts. with RS >25 or N2-3 pts with RS ≤25 and ET-response (Ki67post ≤10%) were randomized to (neo)adjuvant standard chemotherapy (CT) or ribociclib + AI +/- GnRH-analog (n=1,670 randomized). Participation of premenopausal pts. with N1-disease and RS ≤25 or N0 and RS 16-25 was allowed irrespective of ET-response, but randomization recommended only for ET-responders. Use of OFS + TAM or AI for ET response assessment in the preoperative phase was protocol-recommended. This analysis includes all patients with baseline RS and data on ET-response. Ki67-response is defined as Ki67post ≤10% (central pathology assessment) after 2-4 weeks of therapy (OFS-use recommended for 4 weeks). ER-, PR-, and HER2-levels are analyzed by IHC and mRNA. Results Results on ET-response according to age and clinicopathological as well as tumor biological characteristics will be presented at the meeting. So far, ADAPTcycle with >5,000 pts. screened is the largest trial worldwide to look at ET response assessment in pre- and postmenopausal pts. with HR+/HER2- EBC. The results thus have the potential to impact clinical practice. Contact Information oleg.gluz@wsg-online.com Citation Format: Oleg Gluz, Matthias Christgen, Ulrike Nitz, Sherko Küemmel, Michael Braun, Marc Thill, Rachel Wuerstlein, Pauline Wimberger, Andreas Hartkopf, Christian Schem, Matthias Zaiss, Vesna Bjelic-Radisic, Marianne Just, Kristina Veselinovic, Myriam Vincent, Monika Graeser, Katja Krauss, Oliver Hoffmann, Kerstin Lüdtke-Heckenkamp, Ronald Kates, Christine zu Eulenburg, Peter Schmid, Rick Baehner, Hans-Heinrich Kreipe, Nadia Harbeck. Impact of age and ovarian function suppression (OFS) on endocrine response to short preoperative endocrine therapy (ET): Results from the multicenter WSG-ADAPTcycle trial (n=5,290) [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 PO3-18-10.

Abstract PO4-01-12: Efficacy of neoadjuvant dose-dense versus standard chemotherapy regimens in ER+ HER2-negative breast cancer: a single-center matched-cohort study. Exploratory analysis of immune markers

Abstract Introduction: Dose-dense adjuvant CT improves long-term outcomes, which has been proved in clinical trials and meta-analysis. However, the efficiency of thе modern dose dence (dd) anthracycline-taxane (A-T) sequential regimens in the neoadjuvant (NA) setting of ER+HER2- breast cancer (BC) has not been assessed. Tumour-infiltrating lymphocytes (TILs) play a key role in the formation of anti-tumor immunity and can be one of the markers of treatment efficacy and prognosis. Studies evaluating TILs in ER+ BC have mixed results. Materials and methods. The aim of the study was to assess the rate of RCB 0-I of 4xddAC (doxorubicine/cyclophosphamide)–T (4xdocetaxel once every 3 weeks or 12xpaclitaxel weekly) NA chemo compared to standart regimen and to study the subpopulation composition of the lymphoid infiltrate and its effect on achieving RCB 0-I. RCB 0-I as a primary end point was chosen due comparable long-term results in ER+HER2- BC as per meta-analisys. Results: The study included pts with stage II-III ER+(ER≥10%) HER2- BC who received NA A-T chemo in a single center from Jan 2017 to Aug 2022. The majority of patients (85,2%) had stage III disease. Statistical hypothesis: NA ddAC–T chemo would increase the rate of RCB 0-1 to 32% from 22% with ACq3w (once every 3 weeks)-T, with a study power of 80%, ά = 0.05, 138 patients should be included in the study. A total of 315 patients were included, 147 received ddAC-T and 168 - ACq3w-T. After propensity matching analysis 138 patients in each group were included in the final analysis. TILs were studied in core-biopsy samples before NA chemo in 79 patients by flow cytometry. The following 8 subpopulations of lymphocytes were assessed as percentage in the cell pool: CD3+, CD3+CD4+, CD3+CD8+, CD4+CD127+CD25+, CD3-CD19+, CD3-CD16+CD56+, CD3+CD16+CD5+, CD8+CD279+(PD-1). The results are presented in medians (Me) due to abnormal distribution. The RCB 0 rate was 18.8% in the ddAC-T group vs 14.5% in the ACq3w-T group (p=0.379), RCB 0-1 - 33.3% vs 21.7% respectively (p=0.04). According to subgroup analysis, significant benefit of ddAC regimen found in patients ≤ 50 y.o., cN0, with PR ≥20%. For the following populations of TILs significant differences in Me for RCB0-I vs RCB II-III were observed: CD3+CD8+, CD3–CD19+, CD3–CD19+, CD8+CD279+. In multivariative analisys CD8+CD279+(PD-1)≤Me proved to be an independent predictive factor for RCB 0-I (p=0,048). Immunological signature CD8+CD279+ ≤ Me, CD3+CD8+ ≤ Me, CD4+CD25+ > Me, CD3-CD19+ > Me was associated with the rate of 66,7% of RCB 0-I vs 0% with the signature with the opposite values. Conclusion: ddAC-T NA chemo compared to standart regimen in ER+HER2- BC increases RCB0-1 rate. CD8+CD279+(PD-1)≤Me is an independent predictive factor for RCB 0-I. Citation Format: Elena Kovalenko, Elena Artamonova, Yaroslav Zhulikov, Maxim Khoroshilov, Alexander Petrovskiy, Igor Vorotnikov, Tatiana Zabotina, Zaira Kadagidze. Efficacy of neoadjuvant dose-dense versus standard chemotherapy regimens in ER+ HER2-negative breast cancer: a single-center matched-cohort study. Exploratory analysis of immune markers [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 PO4-01-12.