Neoadjuvant Chemotherapy Response Research Articles

Abstract PO5-01-04: HER2 Amplification Level and Focal/Broad Region Size as Predictors of Treatment Response in Neoadjuvant Chemotherapy and Anti-HER2 Therapy for HER2-Positive Breast Cancer

Abstract Background: Neoadjuvant chemotherapy combined with anti-HER2 therapy has become the standard treatment approach for HER2-positive breast cancer. However, not all HER2-positive patients can achieve pathological complete response after neoadjuvant therapy. This raises the question of which subset of HER2+ patients derive the greatest benefit from pre-operative HER2-targeted treatment. Therefore, this study aims to determine whether the level and amplification region size of HER2 amplification are associated with the efficacy of neoadjuvant chemotherapy combined with anti-HER2 therapy. Methods: A total of 523 breast cancer samples were collected from 2017 to 2018, among which 202 cases were HER2-positive patients. Among these, 55 HER2-positive patients received neoadjuvant chemotherapy combined with anti-HER2 targeted therapy. The amplification status of HER2 was assessed using immunohistochemistry/fluorescence in situ hybridization (IHC/FISH) and next-generation sequencing (NGS). The HER2/CEP17 ratio, determined by FISH, was used to represent the amplification level of HER2. The size of the amplification region was calculated using NGS and neighboring genes located in chr17q. Amplification regions smaller than 1 Mb were classified as focal amplification, while those larger than 1 Mb were classified as broad amplification. Results: We compared the HER2/ERBB2 status of 523 breast cancer patients using different detection methods and found a high concordance between ERBB2 amplification detected by NGS and HER2-positivity detected by IHC and FISH, with a sensitivity of 96.0%, specificity of 97.8%, and overall concordance of 97.1%. Based on the HER2/CEP17 ratio determined by FISH, we observed that using a threshold of 6 for classification, the high amplification group had a significantly higher pCR rate compared to the low amplification group (86.7% vs. 41.7%; p=0.037, odds ratio [OR]=0.121, 95% confidence interval [CI]: 0.009-0.919). Moreover, the focal amplification group showed a higher pCR rate compared to the broad amplification group (65.9% vs. 30.8%, p=0.051, OR=0.237, 95% CI: 0.045-1.035). Additionally, within the low amplification group (HER2/CEP17 < 6), the pCR rate was 66.7% for focal amplification and 20% for broad amplification, suggesting that focal amplification of ERBB2 may further guide clinical benefit in the low HER2/CEP17 ratio group. Conclusion: This study demonstrates a high concordance between ERBB2 amplification determined by NGS and HER2-positivity determined by IHC/FISH. High HER2/CEP17 ratio and focal amplification of ERBB2 are associated with a higher pCR rate in neoadjuvant chemotherapy combined with anti-HER2 targeted therapy. Citation Format: Ning Liao, Guochun Zhang, Xinze Lv, Kai Li, Ting Hou, Zhou Zhang. HER2 Amplification Level and Focal/Broad Region Size as Predictors of Treatment Response in Neoadjuvant Chemotherapy and Anti-HER2 Therapy 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 PO5-01-04.

Abstract PO1-27-06: HER2 Amplification Level and Focal/Broad Region Size as Predictors of Treatment Response in Neoadjuvant Chemotherapy and Anti-HER2 Therapy for HER2-Positive Breast Cancer

Abstract Background: Neoadjuvant chemotherapy combined with anti-HER2 therapy has become the standard treatment approach for HER2-positive breast cancer. However, not all HER2-positive patients can achieve pathological complete response after neoadjuvant therapy. This raises the question of which subset of HER2+ patients derive the greatest benefit from pre-operative HER2-targeted treatment. Therefore, this study aims to determine whether the level and amplification region size of HER2 amplification are associated with the efficacy of neoadjuvant chemotherapy combined with anti-HER2 therapy. Methods: A total of 523 breast cancer samples were collected from 2017 to 2018, among which 202 cases were HER2-positive patients. Among these, 55 HER2-positive patients received neoadjuvant chemotherapy combined with anti-HER2 targeted therapy. The amplification status of HER2 was assessed using immunohistochemistry/fluorescence in situ hybridization (IHC/FISH) and next-generation sequencing (NGS). The HER2/CEP17 ratio, determined by FISH, was used to represent the amplification level of HER2. The size of the amplification region was calculated using NGS and neighboring genes located in chr17q. Amplification regions smaller than 1 Mb were classified as focal amplification, while those larger than 1 Mb were classified as broad amplification.> Results: We compared the HER2/ERBB2 status of 523 breast cancer patients using different detection methods and found a high concordance between ERBB2 amplification detected by NGS and HER2-positivity detected by IHC and FISH, with a sensitivity of 96.0%, specificity of 97.8%, and overall concordance of 97.1%. Based on the HER2/CEP17 ratio determined by FISH, we observed that using a threshold of 6 for classification, the high amplification group had a significantly higher pCR rate compared to the low amplification group (86.7% vs. 41.7%; p=0.037, odds ratio [OR]=0.121, 95% confidence interval [CI]: 0.009-0.919). Moreover, the focal amplification group showed a higher pCR rate compared to the broad amplification group (65.9% vs. 30.8%, p=0.051, OR=0.237, 95% CI: 0.045-1.035). Additionally, within the low amplification group (HER2/CEP17 < 6), the pCR rate was 66.7% for focal amplification and 20% for broad amplification, suggesting that focal amplification of ERBB2 may further guide clinical benefit in the low HER2/CEP17 ratio group. Conclusion: This study demonstrates a high concordance between ERBB2 amplification determined by NGS and HER2-positivity determined by IHC/FISH. High HER2/CEP17 ratio and focal amplification of ERBB2 are associated with a higher pCR rate in neoadjuvant chemotherapy combined with anti-HER2 targeted therapy. Citation Format: Ning Liao, Guochun Zhang, Xinze Lv, Kai Li, Ting Hou, Zhou Zhang. HER2 Amplification Level and Focal/Broad Region Size as Predictors of Treatment Response in Neoadjuvant Chemotherapy and Anti-HER2 Therapy 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 PO1-27-06.

Abstract PO4-25-03: Comprehensive immune profiling reveals factors associated with neoadjuvant chemotherapy response in triple negative breast cancer

Abstract Background: KEYNOTE-522 has resulted in FDA approval of the immune checkpoint blocker pembrolizumab with neoadjuvant chemotherapy for patients with high-risk triple negative breast cancer (TNBC), given the remarkable improvement in pCR rate to 65% along with improvement in event free survival, while with chemotherapy alone, the pCR rate is 40-50%. Unfortunately, use of pembrolizumab is associated with several immune related adverse events (irAE), some of which can be life-threatening and debilitating, including cardiomyositis, encephalitis, and adrenal insufficiency, among others. Hence, there is an unmet need to identify biomarkers in the tumor microenvironment which could predict patients who may attain pCR with chemotherapy alone and be spared the side effects from the added PD-1 inhibition. Methods: Comprehensive immune profiling, including PD-L1 IHC and the expression of 395 immune genes by RNA-seq, was performed on 1:2 matched FFPE tumor samples from 23 stage 1-3 TNBC patients (2 stage 1, 6 stage 2, 15 stage 3). All patients were female with an average age of 48 years (range: 25-79 years). 14 patients were treated with neoadjuvant chemotherapy alone (NAC) and 9 were treated with neoadjuvant chemotherapy combined with the checkpoint inhibitor pembrolizumab (NAC+I). mRNA expression signatures of tumor inflammation (TIGS, weak/moderate/strong), cell proliferation (CP, poor/moderate/high), and cancer testis antigen expression burden (CTAB) were determined by RNA-sequencing. Statistical comparisons of quantitative biomarkers between groups were calculated using the Wilcoxon Rank-Sum test, overrepresentation analysis of categorical variables between groups was calculated by proportions test, and survival differences were quantified by Cox proportional hazards analysis. Pathological responses were documented as pathological complete response (pCR) vs. non-pCR. Results: Across the entire cohort, patients with a BMI < 30 had significantly higher PD-L1 expression (assessed by RNA) than those with a BMI ³ 30 [p=0.047]. While not a statistically significant association, the NAC+I group tended to have a higher pCR rate compared to the NAC group [44.4% vs. 28.6%, p=0.66]. Across the entire cohort, tumors with high CTA expression, designated as CTAB high, had a higher pCR rate than CTAB low tumors [54.5% vs 16.7%, p=0.089]. No significant difference in pCR rate between TIGS or CP groups was detected for the NAC group, but in the NAC+I group, highly proliferative tumors had a lower pCR rate than moderately proliferative tumors [0% vs. 80%, p=0.048]. The pCR and non-pCR groups for each treatment type also exhibited distinct gene expression profiles. Among the NAC group, underexpression of FOXP3 and overexpression of MAPK14 and CD44 were associated with pCR [p≤0.031], while underexpression of IFNB1, MAPK14, and CD44 was associated with non-pCR [p≤0.029]. Among the NAC+I group, overexpression of CXCR4, TNFR and CCL20 was associated with non-pCR [p≤0.046]. Interestingly, SDHA was significantly overexpressed in the non-pCR subset of patients in the NAC group and significantly underexpressed in the non-pCR subset of patients in the NAC+I group [p≤0.031]. Conclusions: The development of biomarkers of treatment response is essential to the integration of immunotherapy with chemotherapy as a combined cancer treatment. Our study profiled the immune context of both NAC and NAC+I and identified several key microenvironmental differences underlying divergent treatment response in both groups. A comprehensive understanding of these factors could potentially predict pCR to chemotherapy alone, enabling the avoidance of the unnecessary treatment of these tumors with immunotherapy. Citation Format: Robert Seager, Heidi Ko, Sarabjot Pabla, Maria-Fernanda Senosain, Pawel Kalinski, Erik Van Roey, Shuang Gao, Kyle Strickland, Rebecca Previs, Mary Nesline, Stephanie Hastings, Shengle Zhang, Jeffrey Conroy, Taylor Jensen, Marcia Eisenberg, Brian Caveney, Eric Severson, Shakti Ramkissoon, Shipra Gandhi. Comprehensive immune profiling reveals factors associated with neoadjuvant chemotherapy response 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 PO4-25-03.

Abstract PO1-02-07: HER2 Low Non-Metastatic Breast Cancer in Qatar: A Nationwide Retrospective Cohort Study to Evaluate the Response to Neoadjuvant Chemotherapy: A Real-World Analysis

Abstract Background: Breast Cancer is the most diagnosed cancer type worldwide and the second leading cause of cancer-related death among women. HER2-low breast cancer is a newly defined molecular subtype of breast cancer in which tumors exhibit a minimal overexpression of HER2 or no gene amplification. To illustrate, HER2-low tumors typically have an IHC score of 1+ or a score of 2+ with negative amplification. However, emerging evidence suggests that even a minimal amplification of HER2 may significantly impact the response to therapy and prognosis. Our study aims to unveil the impact of HER2-low expression on the response to anthracycline and taxane-based neoadjuvant chemotherapy (NACT) in comparison to the HER2-negative group in non-metastatic breast cancer. The primary objective was evaluating the response to NACT comparing the favorable response (complete and partial response) in each of the two groups of HER2-low and HER2-negative patients. Methods: This is a retrospective cohort study. All patients’ profiles with non-metastatic, HER2-Low, and HER2-negative breast cancers who received neo-adjuvant chemotherapy and underwent surgery between the 1st of January 2018 and the 30th of August 2022 were included. Patients' response was evaluated using surgical pathology reports to compare the two study groups (HER2-low and HER2-negative). Results: The total number of patients included was 262 patients, the majority were HER2-low 89% (233/262) vs. 11% (29/262) HER2-negative. A favorable response to NACT was shown in 71% (185/262) of all patients. The favorable response rate was similar in both groups, 70% (164/233) in the HER2-low group vs. 72% (21/29) in the HER2-negative group, OR: 1 (95% CI: 0.8-1), p-value 0.8. Similarly, the pathological complete response (pCR) rate was the same in both study groups at 14%, OR: 0.7 (95% CI: 0.2-3), p-value: 0.6. Interestingly, patients with hormone-positive tumors across both study groups had a higher response rate as compared to hormone-negative patients. However, statistical significance was shown in the HER2-low group only. In the HER2-low cohort, 73% of the patients (119/164) with hormone-positive tumors showed a favorable response OR: 0.8 (95% CI: 0.8- 1), p-value: 0.001. Comparatively, in the HER2-negative cohort, 52% of the patients (11/21) with hormone-positive tumors had a favorable response OR: 2 (95% CI: 1– 5), p-value: 0.05. Conclusion: Our results did not show any significant impact of HER2-low expression on neoadjuvant chemotherapy response. Nonetheless, a statistically significant difference in response was observed in the hormone-positive HER2-low breast cancer patients. Further studies are needed to evaluate the influence of hormonal expression on the response rate to NACT in the HER2-low patient population. Citation Format: Ahmed Kardousha, Wafaa Shehada, Ahmed Basha, Sahar Nasser, Mufid el Mistiri, Anas Hamad, Salha Al-Bader, Shereen Elazzazy. HER2 Low Non-Metastatic Breast Cancer in Qatar: A Nationwide Retrospective Cohort Study to Evaluate the Response to Neoadjuvant Chemotherapy: A Real-World Analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-02-07.

Abstract PS04-03: Survival benefit of regional nodal irradiation in clinically node-positive breast cancer following neoadjuvant chemotherapy and breast-conserving surgery

Abstract Introduction: In recent years, there has been increasing use of neoadjuvant chemotherapy (NAC) and pathologic complete response (pCR) rates for certain breast cancer phenotypes (40-70%). Although encouraging, this has resulted in uncertainties in traditional axillary management. Meanwhile, clinically node-positive (cN+) patients who have a low burden of disease downstaged to node-negative (ypN0) after NAC and get breast-conserving surgery (BCS) may avoid an axillary lymph node dissection (cALND) but still have regional nodal irradiation (RNI) recommended regardless of axillary surgery. Those who remain node-positive (ypN+) undergo cALND and RNI with an increased risk of lymphedema. In this study, we evaluated the survival benefit of RNI in cN+ patients after NAC and BCS. Methods: We reviewed (cN+) stage I-III non-inflammatory female breast cancer patients who underwent NAC followed by BCS between 2010 and 2020 in the National Cancer Database (NCDB). Patients having a history of another malignancy who received hormone therapy or radiotherapy before surgery or whose pathologic nodal status (ypN) was unknown were excluded. Overall survival (OS) from surgery was compared between those who did and did not receive RNI. Patient and tumor characteristics were compared across subgroups using chi-square and Wilcoxon rank sum tests. Weighted Kaplan-Meier curves and log-rank tests were used to assess the effect of RNI on OS. As a sensitivity analysis, analyses were stratified based on yPN status. Finally, multivariable logistic regression was used to determine predictors of receiving RNI. Results: The 8,250 cN+ patients had a mean age of 54.6±11.1 years. In total, 69.1% of patients were White, 23.9% were Black, and 10.2% were Hispanic. The mean number of removed and positive nodes were 10.0 ±7.8 and 2.3±3.8. The most common histology and phenotype were invasive ductal carcinoma (IDC) in 94.3% and hormone-positive (HR+) in 41.0%. Breast and nodal pCR rates were 25.9% and 34.7%, with nodal pCR achieved in 20.7%, 46.0%, and 44.4% of HR+, HER2+, and triple-negative tumors. RNI was performed in 52.1% of the patients (45.3% of the yPN0 and 55.9% of the yPN+). The mean number of nodes removed was 10.4±7.8 in the RNI+ and 9.6±7.7 in the RNI- groups (P < 0.01). The mean number of positive nodes was 2.6±4.0 in the RNI+ and 1.9±3.6 in the RNI- groups (P < 0.01). On multivariable analysis, the predictors of RNI administration included the number of positive nodes (p < 0.01), cN stage (p < 0.01), cT3 (p < 0.01), and tumor phenotype (p < 0.01). Grade I tumors (p=0.04) and Medicare beneficiaries (p=0.01) were less likely to get RNI. The survival rates were 79.9% and 81.9% in the RNI+ and RNI– groups, with a median follow-up of 62.1±31.4 and 62.8±32.2 in the RNI+ and RNI- groups. In the entire cohort, ypN0 patients had improved OS when compared with ypN+ patients (p < 0.001), but in adjusted analyses, there was no difference in OS between those who did and did not receive RNI (p=0.6). There was also no difference in OS comparing those who did and did not receive RNI in the ypN0 (p=0.96) or ypN+ (p=0.76) groups. Conclusion: For breast cancer patients having a modest nodal burden of disease and BCS after NAC, traditional prognostic factors such as stage and nodal status, as well as phenotype, grade, and the presence or absence of pCR, impact overall survival. Although some such factors appear to bias practitioners into giving RNI for patients undergoing NAC and BCS, RNI after NAC and BCS does not improve OS, regardless of pCR status, even at a mean follow-up time of 5.5 years. Further studies evaluating the impact on local control and longer-term outcomes should be pursued to enable the creation of specific guidelines surrounding indications for RNI based on the initial burden of disease and the final response from NAC administration. Citation Format: Mahtab Vasigh, Richard Bleicher, Austin Williams, Allison Aggon, Mary Pronovost, Andrea Porpiglia, Matthew Pierotti, Christian Cruz Pico. Survival benefit of regional nodal irradiation in clinically node-positive breast cancer following neoadjuvant chemotherapy and breast-conserving surgery [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 PS04-03.

Abstract PO3-16-01: Personalized circulating tumor DNA assay precisely predicts the response of neoadjuvant chemotherapy in breast cancer patients

Abstract Introduction Circulating tumor DNA (ctDNA), which is detected in the blood as cell free DNA fragment from tumor cells, could indicates genomic landscape, tumor burden and treatment response during chemotherapy as a non-invasive method. Especially, personized ctDNA assay by next-generation sequencing(NGS) is able to detect a trace amount of ctDNA and precisely figure out the change of the amount of ctDNA during NAC and follow up period after curative surgery. Here, we performed serial ctDNA evaluations in EBC patients who diagnosed as TNBC or HER2-positive BC and received NAC followed by curative surgery. We aimed to predict NAC response and detect minimal residual disease (MRD) using personalized ctDNA assay. Methods CtDNA was detected by AlphaLiquid®Detect, a tumor-informed personalized MRD detection assay exploring most of the mutations in tumor. Whole exome sequencing (WES) of tumor tissue and peripheral blood mononuclear cells (PBMCs) was performed. Patient-specific somatic mutations were selected using a proprietary algorithm. In brief, clonal variants were prioritized using integrated information including variant allele frequency, population allele frequency databases, somatic variant databases, variant pathogenicity, and genomic context. Up to 100 variants were selected for patient monitoring. A hybridization capture panel consisting of a pool of 4 patients’ selected variants was synthesized. These bespoke panels (BSPs) were used for ctDNA detection. Patients with more than 2 tumor-derived mutations detected in plasma were considered as ctDNA positive. Inclusion criteria included patient who diagnosed as stage IIA-IIIC BC planned to NAC followed by curative surgery. Among BC subtypes, TNBC and HER2-positive BC were allowed. Collection of specimens and associated clinical data used in this study was approved by the Institutional Review Board of Samsung Medical Center (IRB File No.2021-02-033), and we received informed consents for this study. Results From May 2021 to Sep 2022, 158 patients has been enrolled. Archival tissues were not available in 47 patients and tissue WES had failed in six patients. Therefore, 105 patients were enrolled and analyzed their ctDNA at diagnosis based on tissue WES data. Of 105 patients, Median age of BC patients was 49.3 years of age (range: 26.1, 67.8). Thirty-six patients (34.3%) were post-menopausal status and others (65.7%) were pre-menopausal status. In BC pathology at diagnosis, 56 (53.3%) were TNBC and other 49 (46.7%) were HER2-positive BC. Among HER2-positive BC, hormone receptor (HR)-positive were in 21 (20.0%). In clinical stage at diagnosis, stage II were 46 (43.8%) and stage III in 59 (56.2%). In 105 patients, median number of somatic mutations was 60 (interquartile range [IQR]: 38.5, 91). CtDNA detection rate at BC diagnosis was 90.5% and all of BC which not be detected ctDNA was HER2-positive BC with clinical stage II. Median amount of ctDNA at diagnosis was 20 (IQR: 6, 44). In the number of somatic mutations, there was no difference according to BC subtypes (P=0.121) and clinical stage (P=0.700) but the amounts of ctDNA at diagnosis was different. CtDNA was much more detected in TNBC compared to HER2-positive BC (Median: 34.5 vs. 15.9; P< 0.001) and clinical stage III compared to clinical stage II (Median 33.2 vs. 19.5; P=0.002). After NAC, ctDNA at curative surgery was tested in 70 patients. In 70 patients, pathologic complete response(pCR) was observed in 44 patients. CtDNA was detected in ten patients (14.3%) and eight did not achieve pCR and two with pCR (Specificity of assay: 95.5%, positive predictive value: 0.80, P=0.032). Conclusions Personalized ctDNA assay can precisely detected ctDNA at diagnosis and their detection rate was associated with BC subtypes and clinical stage. In addition, ctDNA at curative surgery also can predict NAC response in EBC patients. Long term ctDNA follow up of MRD would be warranted. Citation Format: Ji-Yeon Kim, Hae Hyun Jung, Jeong Eon Lee, Seok Won Kim, Hwang-Phill Kim, Sunghoon Heo, Jongseong Ahn, Tae-You Kim, Young-Hyuck Im. Personalized circulating tumor DNA assay precisely predicts the response of neoadjuvant chemotherapy in breast cancer patients [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 PO3-16-01.

Abstract PO3-15-11: Soluble sFas, sFasL, sPD1, and sPD-L1 analyses in the blood peripheral of locally advanced breast cancer women before and after neoadjuvant chemotherapy

Abstract Assess soluble sFAS, sFASL, sPD1, and sPD-L1 levels in patients with HER2 or triple-negative (TN) breast cancer submitted to neoadjuvant chemotherapy. A prospective cohort study was performed with TN and HER2+ breast cancer patients between 2015 and 2018. Soluble levels of sFasL, sFas, sPD-L1, and sPD1 were collected before and after neoadjuvant chemotherapy (NAC). NAC regimens included a dense dose of Adriablastin and cyclophosphamide during four cycles, followed by Paclitaxel for 12 weeks. No clinical evidence of tumor in the breast and axillary lymph nodes was defined as a pathological complete response (pCR). Twenty-one women with TN (56,7%) and 16 (43,3%) HER2+ breast cancer were included. Twenty-one women (56.7%) presented complete pathological response (pCR) after neoadjuvant chemotherapy (NAC), defined as the absence of invasive disease in the breast and lymph nodes. High sPD1 and sFas levels in the TN and HER2+ patients compared to the control group (P< 0.05). In paired analysis, statistical differences of sFas and sFasL levels in TN and HER2+ patients before and after NAC (P< 0.05). Low levels of sPDL1 in HER2+ patients with pCR compared to non-pCR (P< 0.05). High sFasL levels in TN patients with pCR compared to the non-pCR group (P< 0.05). Conclusion: soluble sFas, sFas-L, sPD1, and sPD-L1 levels were apoptosis-related markers with potential predictive value of neoadjuvant chemotherapy response in TN and HER2+ breast cancer. Keywords: breast cancer; FAS receptor; Programmed death 1, HER2+, Triple negative Citation Format: Carolina Vasconcelos, Marcelo Salgado, Carlos Eduardo Anunciação, Denise Viana, Leuridan Torres, Nathália Valois Montarroyos de Moraes. Soluble sFas, sFasL, sPD1, and sPD-L1 analyses in the blood peripheral of locally advanced breast cancer women before and after neoadjuvant 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 PO3-15-11.

Abstract PO2-01-10: 21-Gene Recurrence Score Index (ONCOTYPE DX) as a predictive biomarker for neoadjuvant chemotherapy response and outcome in patients with HR+HER2- breast cancer

Abstract Background: Hormone receptor positive (HR+), HER2- early stage breast cancer (EBC) has shown lower response to neoadjuvant chemotherapy (NCT) compared with other clinicopathologic subtypes. ONCOTYPE DX may help inform systemic treatment decisions for EBC and predicting likelihood of pathological complete response (pCR) or chemosensitivity. We analyze the pathologic response according ONCOTYPE RS and their prognostic value. Methods: We included a serie of 139 consecutive patients with high clinical risk factor with criteria to received NCT than have performed an ONCOTYPE DX test previous to start NCT. The median age was 51 years with 65 patients (47%) less than 50 years. Median initial tumoral size was 25 mm (9-97), T1: 35%, T2: 51% and T3: 14%. 70 patients (50%) have initial axillary node involvement. Median ONCOTYPE DX score was 29 (12 – 76) , RS < 25 in 36% and RS < 30 in 54%. Complete pathologic response (pCR) was found in 35 patients (25%), and by RCB was: RCB:0 23%, RCB-1 18%, RCB-2 24% and RCB-3 34%. Results: pCR score was correlated with ONCOTYPE DX (pearson : p:0,001) , patients with ONCOTYPE RS score superior to 30 has a total of 37% of pCR in contrast to a 14% in patients with ONCOTYPE RS score less than 30. Median follow-up was 32 months (5 -100). The rate of recurrence was similar independently the ONCOTYPE RS score (12% < 30 ; 15% >30) , but patients with ONCOTYPE RS < 30 with achieve pCR had better prognostic compared to patients that not achieve pCR (0% vs 14%). Patients with ONCOTYPE RS > 30 tumors that had a pCR the recurrence rate was 8% compared to 20% in patients with non pCR. Conclusions: These data suggest ONCOTYPE DX predicts pCR in HR+HER2- BC patients, especially in patients with a RS superior to 30 with an high rate of pCR of 37%. Patients with ONCOTYPE DX less than 30 that achieved pCR had the better outcomes and patients with ONCOTYPE DX superior to 30 that not achieved pCR had the worst outcomes with a total of 20% of recurrence. ONCOTYPE DX predicts the possibility of achieve a pCR and patients with a high ONCOTYPE DX RS score with residual disease have a high recurrence despite receiving treatment with chemotherapy, which requires a better adjuvant treatment, possibly with CDK 4/6 cyclin inhibitors. Citation Format: Ariadna Gasol Cudós, Serafin Morales Murillo, Noemí Tuset Der-Abrain, Felip Vilardell Villellas, Laura Arbones Cid, Jordi Melé Olivé, Carles Canosa Morales. 21-Gene Recurrence Score Index (ONCOTYPE DX) as a predictive biomarker for neoadjuvant chemotherapy response and outcome in patients with HR+HER2- breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-01-10.

Abstract PO5-07-03: Integrating mechanism-based and data-driven modeling to predict the response of triple negative breast cancer to therapy

Abstract Introduction Neoadjuvant chemotherapy (NAC) is the standard-of-care (SOC) for patients with locally advanced triple-negative breast cancer (TNBC) [1]. Unfortunately, only about half of TNBC patients achieve a pathological complete response (pCR) at the completion of NAC [2]. With the recent FDA approval of immunotherapy, the response rate improved by about 8% [3]. To try to further improve NAC response rates, we build upon methods that predict treatment response to optimize interventions and outcomes. Our previous studies have demonstrated that excellent predictive accuracy of TNBC response to NAC was achieved through calibrating mechanism-based models to both pre- and on- treatment imaging data [4]. However, by requiring on-treatment imaging data, therapy optimization can only occur after a patient begins NAC. Here, our goal is to relax the requirement of on-treatment imaging data such that we can predict, and potentially optimize, a patient’s response to NAC before initiating it. We will accomplish this through combining data-driven approaches with mechanism-based modeling to obtain spatiotemporal predictions of tumor response prior to NAC. More specifically, we integrate a reaction-diffusion equation based mathematical model with a U-Net based convolutional neural network (CNN). Methods The reaction-diffusion equation models the development of tumor cellularity over time as the sum of tumor cell diffusion, controlled by a fixed diffusivity, and tumor cell proliferation, controlled by a calibrated net proliferation rate. The net proliferation rate implicitly accounts for both proliferative and drug induced death effects. We calibrated the net proliferation rates in this model on a patient-specific basis for 128 patients from the ARTEMIS trial (NCT02276443) using three imaging timepoints – pre- (V1), post two cycles (V2), and post four cycles (V3) of A/C. We then employed a CNN to characterize the relationship between the calibrated net proliferation rates and the pre-treatment imaging data. The CNN takes pretreatment imaging inputs of the apparent diffusion coefficient map, percent enhancement maps from the dynamic contrast enhanced MRI timecourse, and precontrast T1 map. The CNN outputs an estimate of the calibrated net proliferation rate which can be used to run the mathematical model forward in time to predict cellularity maps at V2/3. In training the CNN, our loss considers both the concordance correlation coefficient (CCC) and the normalized root mean square error (NRMSE). We calculated loss on the net proliferation rate predictions as NRMSE with a CCC penalty to aid in characterizing the non-Gaussian distribution of the net proliferation rate. We calculated loss on the cellularity predictions as the CCC between predicted and measured voxel-wise cellularity. The CNN was trained using the Adam optimizer and a fivefold cross validation with a withheld test set of 26 patients. Results Using the CNN predictions to forward run the mechanism-based model in time to V3 we calculated change in total tumor cellularity and volume from V1 to V3. In the test cohort, we obtained CCC values between the predicted and measured changes of 0.95 and 0.91 for cellularity and volume, respectively. Discussion and summary Through integrating mechanistic modeling and deep learning, we can accurately predict the spatiotemporal development of TNBC response to NAC using only pretreatment imaging data. We will build upon these results by expanding our model to include separate proliferation and drug induced death terms to allow for therapy intervention and optimization. Additionally, we will incorporate other pretreatment data types including genetic data. [1] Liedtke et al., J of Clin Oncol, 2008. [2] Spring et al., Clin Cancer Res, 2020. [3] Schmid et al., NEJM, 2020. [4] Wu et al., Cancer Res, 2022. Citation Format: Casey Stowers, Chengyue Wu, Sidharth Kumar, Zhan Xu, Clinton Yam, Jong Bum Son, Jingfei Ma, Jonathan Tamir, Gaiane Rauch, Thomas Yankeelov. Integrating mechanism-based and data-driven modeling to predict the response of triple negative breast cancer to therapy [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 PO5-07-03.

Abstract PO3-25-06: Expression of CD28, Fas, PD1, and CTLA4 molecules on cellular immune response in the blood peripheral of patients with locally advanced triple-negative breast cancer

Abstract Background: Locally advanced triple-negative breast cancer (TNBC) represents a public health problem in Brazil; its standard treatment consists of neoadjuvant chemotherapy followed by surgical and radiotherapy, with highly variable success rates are depended on access to appropriate cancer treatment, and the type of pathological response. In the last decade, the immune system's role in breast cancer has gained space by demonstrating the favorable impact of lymphocyte tumor infiltrate (TILs) and gene expression of the immune response, especially in tumors with high proliferation rates and negative estrogen receptors. The cellular immune response is regulated by co-stimulatory and co-inhibitory proteins such as CD28, Fas, PD1, and CTLA4 molecules. Methods: This was a longitudinal study with follow-up performed between 2015 and 2017. The study was conducted at the Hospital de Cancer de Pernambuco and Translational Research Laboratory of the Instituto de Medicina Integral Prof. Fernando Figueira (IMIP). Thirty women (18 to 60 years) diagnosed with locally advanced TNBC submitted to neoadjuvant chemotherapy (NAC), and 30 healthy women as a control group were included. The co-stimulatory and co-inhibitory proteins analyses were performed in the peripheral blood of TNBC women before (Pre-NAC) and after NAC (Post-NAC) Results: High levels of CD28+CD3+ T, CD28+CD4+ T, PD1+CD3+ T, and CTLA4+CD3+ T cells in the pathological complete response (pCR) and non-pCR groups compared to the control group (p < 0.05). High levels of Fas+CD4+T cells and PD1+CD8+T cells in the non-pCR compared to the pCR group (p < 0.05). In the paired analysis, significant differences were observed in CD3+T and CD4+T levels with CD28, Fas, and PD1 expression between pre- and post-NAC. Conclusion: Fas+CD4+T and PD1+CD8+T levels in peripheral blood in TNBC are associated with pCR, suggesting potential predictive biomarkers of NAC response. Preliminary results allow us to infer that neoadjuvant chemotherapy modulates the cellular immune response in TNBC women. Citation Format: Marcelo Salgado, Fernando Soares, Denise Viana, Amanda Salgado, Carolina Vasconcelos, Carlos Eduardo Anunciação, Eduardo Salgado, Leuridan Torres. Expression of CD28, Fas, PD1, and CTLA4 molecules on cellular immune response in the blood peripheral of patients with locally advanced triple-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-25-06.

Clinicopathologic and molecular correlates to neoadjuvant chemotherapy-induced pathologic response in breast angiosarcoma.

Both primary and secondary breast angiosarcoma (AS) are characterized by multifocal presentation and aggressive behavior. Despite multimodality therapy, local and distant relapse rates remain high. Therefore, neoadjuvant chemotherapy (NACT) is employed to improve the R0 resection rates and survival, but its benefits remain controversial. Herein, we investigate pathologic and molecular correlates to NACT-induced histologic response in a group of 29 breast AS, 4 primary and 25 radiation-associated (RA). The two NACT regimens applied were anthracycline- and non-anthracycline-based. The pathologic response grade was defined as: I: ≤ 50%, II: 51%-90%, III: 91%-99%, and IV: 100%. An additional 45 primary AS and 102 RA-AS treated by surgery alone were included for survival comparison. The genomic landscape was analyzed in a subset of cases and compared to a cohort of AS without NACT on a paired tumor-normal targeted DNA NGS platform. All patients were females, with a median age of 31 years in primary AS and 68 years in RA-AS. All surgical margins were negative in NACT group. The NACT response was evenly divided between poor (Grades I-II; n = 15) and good responders (Grades III-IV; n = 14). Mitotic count >10/mm2 was the only factor inversely associated with pathologic response. By targeted NGS, all 10 post-NACT RA-AS demonstrated MYC amplification, while both primary AS harbored KDR mutations. TMB or other genomic alterations did not correlate with pathologic response. All four patients with Grade IV response remained free of disease. The good responders had a significantly better disease-specific survival (p = 0.04). There was no survival difference with NACT status or the NACT regimens applied. However, NACT patients with MYC-amplified tumors showed better disease-free survival (p = 0.04) compared to MYC-amplified patients without NACT. The overall survival of NACT group correlated with size >10 cm (p = 0.02), pathologic response (p = 0.04), and multifocality (p = 0.01) by univariate, while only size >10 cm (p = 0.03) remained significant by multivariate analysis.

Implementing Standard Diagnosis and Treatment for Locally Advanced Breast Cancer Through Global Research in Latin America: Results From a Multicountry Pragmatic Trial.

Breast cancer mortality rates in Latin America (LA) are higher than those in the United States, possibly because of advanced disease presentation, health care disparities, or unfavorable molecular subtypes. The Latin American Cancer Research Network was established to address these challenges and to promote collaborative clinical research. The Molecular Profiling of Breast Cancer Study (MPBCS) aimed to evaluate the clinical characteristics and treatment outcomes of LA participants with locally advanced breast cancer (LABC). The MPBCS enrolled 1,449 participants from Argentina, Brazil, Chile, Mexico, and Uruguay. Through harmonized procedures and quality assurance measures, this study evaluated clinicopathologic characteristics, neoadjuvant chemotherapy response, and survival outcomes according to residual cancer burden (RCB) and the type of surgery. Overall, 711 and 480 participants in the primary surgery and neoadjuvant arms, respectively, completed the 5-year follow-up period. Overall survival was independently associated with RCB (worse survival for RCBIII-adjusted hazard ratio, 8.19, P < .001, and RCBII [adjusted hazard ratio, 3.69, P < .008] compared with RCB0 [pathologic complete response or pCR]) and type of surgery (worse survival in mastectomy than in breast-conserving surgery [BCS], adjusted hazard ratio, 2.97, P = .001). The hormone receptor-negative-human epidermal growth factor receptor 2-positive group had the highest proportion of pCR (48.9%). The analysis of the ASCO Quality Oncology Practice Initiative breast module revealed high compliance with pathologic standards but lower adherence to treatment administration standards. Notably, compliance with trastuzumab administration varied widely among countries (33.3%-88.7%). In LABC, we demonstrated the survival benefit of BCS and the prognostic effect of the response to available neoadjuvant treatments despite an important variability in access to key treatments. The MPBCS represents a significant step forward in understanding the real-world implementation of oncologic procedures in LA.

Predictive Factors of Neoadjuvant Chemotherapy Response in Breast Cancer Validated by Three Anatomopathological Scores: Residual Cancer Burden, Chevallier System, and Tumor-Infiltrating Lymphocytes

Predictive Factors of Neoadjuvant Chemotherapy Response in Breast Cancer Validated by Three Anatomopathological Scores: Residual Cancer Burden, Chevallier System, and Tumor-Infiltrating Lymphocytes

Abstract LB061: Aurora kinases inhibition enhances neoadjuvant chemotherapy response in triple negative breast cancer

Abstract Triple-Negative Breast Cancer (TNBC) is a type of breast cancer without expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor (HER2). TNBC accounts for around 15-20% of all breast cancers, and it remains the most challenging subtype to treat because of its aggressive phenotype and limited treatment strategies. Since TNBC does not respond to endocrine and HER2-targeted therapy, chemotherapy and anti-PD-L1 immunotherapy remain the major treatment strategies so far. However, not all TNBC patients respond to chemotherapy, suggesting that TNBC is a complicated disease. Identifying biomarkers to further predict and subdivide TNBC patients with distinct chemotherapy responses and outcomes is very important. To profile the protein expression and phosphorylation alterations, comprehensive proteogenomics was deployed to probe the molecular basis for differential response to neoadjuvant chemotherapy for TNBC. From a Reverse Phase Protein Array (RPPA) on TNBC cell lines MDA-MB-468 cells and MDA-MB-231 cells treated with Docetaxel, Paclitaxel, Epirubicin, and Doxorubicin, we found only a short list of protein changes after chemotherapy. Among them, the most significant changes in protein are phosphor-AURKA/B/C, AURKA, AURKB, and PLK1, which fall into the mitotic kinase group and are confirmed by western blot analysis. In addition, no significant change in the mRNA level was found after chemotherapy treatment, suggesting a post-transcription level molecular mechanism regulates the upregulation of AURKA and AURKB protein. In fact, the protein level of AURKB decreased more significantly with Cycloheximide (CHX) treatment alone compared with the co-treatment of CHX and Paclitaxel, indicating Paclitaxel extended the lifetime of Aurora Kinases protein and increased the protein stability. Moreover, AURKB or AURKA overexpression in TNBC cells renders them resistant to Paclitaxel treatment and attenuates the apoptosis effect triggered by chemotherapy treatment, suggesting Aurora Kinases could mediate the chemo-resistance in TNBC. To overcome the resistance to chemotherapy, we treated resistant TNBC cells with the combination of Aurora kinase inhibitors and anthracycline/taxane chemotherapy and found that Aurora kinase inhibition significantly enhanced the chemotherapy effect. In summary, we found that Aurora Kinases upregulation by treatment with Taxanes-type and Anthracyclines-type chemotherapy could render chemotherapy resistance to TNBC cells. Citation Format: Jia Xu, Chang Liu, Bohan Ning, Ali Cem Kucukdagli, Yunjia Chen. Aurora kinases inhibition enhances neoadjuvant chemotherapy response in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB061.

Integrative analysis identifies molecular features of fibroblast and the significance of fibrosis on neoadjuvant chemotherapy response in breast cancer.

The molecular features of fibroblasts and the role of fibrosis in neoadjuvant chemotherapy (NAC) response and breast cancer (BRCA) prognosis remain unclear. Therefore, this study aimed to investigate the impact of interstitial fibrosis on the response and prognosis of patients with BRCA undergoing NAC treatment. The molecular characteristics of pathologic complete response (pCR) and non-pCR (npCR) in patients with BRCA were analyzed using multi-omics analysis. A clinical cohort was collected to investigate the predictive value of fibrosis in patients with BRCA. Fibrosis-related signaling pathways were significantly upregulated in patients with npCR. npCR may be associated with distinct and highly active fibroblast subtypes. Patients with high fibrosis had lower pCR rates. The fibrosis-dependent nomogram for pCR showed efficient predictive ability (training set: area under the curve [AUC]=0.871, validation set: AUC=0.792). Patients with low fibrosis had a significantly better prognosis than those with high fibrosis, and those with a high fibrotic focus index had significantly shorter overall and recurrence-free survival. Therefore, fibrosis can be used to predict pCR. Our findings provide a basis for decision-making in the treatment of BRCA. npCR is associated with a distinct and highly active fibroblast subtype. Furthermore, patients with high fibrosis have lower pCR rates and shorter long-term survival. Therefore, fibrosis can predict pCR. A nomogram that includes fibrosis can provide a basis for decision-making in the treatment of BRCA.

Metabolic tumor burden as a prognostic indicator after neoadjuvant chemotherapy in pancreatic cancer.

There is no standardized assessment for evaluating response although neoadjuvant chemotherapy (NAT) is widely accepted for borderline resectable or locally advanced pancreatic cancer (BRPC or LAPC). This study was aimed to evaluate NAT response using positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG-PET/CT) parameters alongside carbohydrate antigen (CA) 19-9 levels. Patients who underwent surgery after NAT for BRPC and LAPC between 2017 and 2021 were identified. The study assessed the prognostic value of PET-derived parameters after NAT, determining cutoff values using the K-adaptive partitioning method. It created four groups based on the elevation or normalization of PET parameters and CA19-9 levels, comparing survival between these groups. Of 200 eligible patients, FOLFIRINOX and gemcitabine-based NAT were administered in 167 and 34 patients, respectively (mean NAT cycles, 8.3). In a multivariate analysis, metabolic tumor volume (MTV) demonstrated the most robust performance in assessing response (HR 3.11, 95% CI 1.73-5.58, P<0.001) based on cut-off value of 2.4. Patients with decreased MTV had significantly better survival than those with elevated MTV among individuals with CA19-9 levels <37IU/L (median survival; 35.5 vs. 20.9mo, P<0.001) and CA19-9 levels ≥37IU/L (median survival; 34.3 vs. 17.8mo, P=0.03). In patients suspected to be Lewis antigen negative, predictive performance of MTV was found to be limited (P=0.84). Elevated MTV is an influential prognostic factor for worse survival, regardless of post-NAT CA19-9 levels. These results could be helpful in identifying patients with a poor prognosis despite normalization of CA19-9 levels after NAT.

Effect of tumor-infiltrating immune cells (mast cells, neutrophils and lymphocytes) on neoadjuvant chemotherapy response in breast carcinomas

IntroductionDespite screening, the incidence of breast cancer is increasing worldwide. Neoadjuvant chemotherapy (NAC) response is one of the most important parameters taken into consideration in surgery, optimal adjuvant chemotherapy planning and prognosis prediction. Research on predictive markers for the response to NAC is still ongoing. In our study, we investigated the relationship between tumor-infiltrating neutrophils/mast cells/lymphocytes and NAC response in breast carcinomas. Material and methodStudy included 117 patients who were diagnosed with invasive breast carcinoma using core needle biopsy. In these biopsies tumor-infiltrating neutrophils/mast cells/lymphocytes were evaluated and Miller Payne Score was used for NAC response. Result53 patients exhibited high TILs, 36 had high TINs, and 46 showed high TIMs. While pathological complete response was 27 % in all patients, it was 38 % in high TINs patients, 35 % in high TILs patients, and 28 % in high TIMs patients. High TIMs were observed to be statistically associated with survival.TILs, TINs, nuclear grade, ER, PR and HER2 expression, Ki-67 proliferation index were found to be associated with the Miller - Payne score. In multivariate analysis, TINs, nuclear grade, pathological stage, and molecular subtype were found to be independent risk factors for treatment response. ConclusionTINs have better prognostic value to predict neoadjuvant treatment than TILs. High TIMs are associated with increased overall survival. The inclusion of TINs in NAC response and TIMs in overall survival in pathology reports and treatment planning is promising in breast carcinomas as they are simple to use and reproducible markers.

Sentinel Lymph Node Biopsy After Neoadjuvant Chemotherapy in cN0 Breast Cancer: Impact of HER2-Positive Status on Survival.

High rates of negative sentinel lymph node biopsy (SLNB) in clinically node-negative (cN0) breast cancer (BC) after neoadjuvant chemotherapy (NAC) have been described. These results are associated with triple-negative (TNBC) and human epidermal growth factor receptor 2 (HER2+) subtypes achieving pathologic complete response (pCR). This study evaluates predictive variables and survival in order to assess the possible omission of SLNB after NAC. Prospective study of women with cN0 BC treated with NAC and subsequent surgery, between April 2010 and May 2021. SLNB technique included, performing axillary lymphadenectomy in the absence of detection or SLNB-positivity. Multivariable logistic regression was used for analysis of NAC-response and SLNB-results in molecular subtypes: HR-/HER2+, TNBC, HR+/HER2- and HR+/HER2+. Kaplan-Meyer and log-rank were used for survival analysis. A total of 179 patients (50.5±10.1 years) were included. Of these, 39.7% achieved pCR (ypT0/Tis). HR-negative subtypes had higher pCR rates (HR-/HER2+: 59.4%; TNBC: 53.4%), with no cases of SLNB-positive. With residual disease, HR-/HER2+ and TNBC showed low rates of SLNB-positivity (6.7% and 10.3%) versus HR+ (HR+/HER2+: 20%; HR+/HER2-: 44%; p<0.001). Multivariable analysis identified independent predictors of SLNB-negativity (p<0.0001) to be: HR- [odds ratio (OR)=0.15; 95% confidence interval (CI): 0.06-0.37; p = 0.0001], HER2+ (OR=0.34; 95% CI: 0.14-0.81; p = 0.015) and high-grade Nottingham (OR=0.42; 95% CI: 0.18-0.99; p = 0.048). Disease-free survival showed worse outcomes with SLNB-positivity (p<0.0001), HR+/HER2- (p = 0.0277), larger tumor size (p = 0.002) and residual disease after NAC (p<0.0001). Patient selection based on NAC response, molecular subtype, and survival outcomes is a priority for establishing individualized therapeutic strategies after NAC. Molecular subtypes with higher pCR rates and lower rates of SLNB-positivity could benefit from non-invasive strategies that include omission of SLNB.

Abstract 2523: Predictive biomarkers for neoadjuvant FLOT4 chemotherapy response in gastroesophageal cancer: Results of multi-omics approach

Abstract Background: The FLOT4 chemotherapy regimen is a standard preoperative treatment for gastroesophageal junction (GEJ) and gastric cancer (GC), yet the response to this treatment is variable. Identification of predictive biomarkers is crucial for optimizing therapeutic strategies. This study aims to identify predictive biomarkers for FLOT4 treatment efficacy using a multi-omics approach. Methods: We conducted a preliminary differential gene expression analysis in diagnostic tissue pre-treatment and surgical resection post-treatment in six patients (two GEJ and four GC) who all exhibited a partial pathological response (G2) to neoadjuvant FLOT4 chemotherapy. Utilizing DESeq2 for differential gene expression and David pathway analysis for functional insights, we have begun to unravel the complex molecular response to treatment. Upcoming assays include blood gDNA and tumor tissue whole exome sequencing (WES), comprehensive methylation profiling, miRNA characterization, and proteomics via LC-MSMS. Results: Our preliminary data suggest alterations in gene expression associated with cell adhesion, extracellular matrix interaction, and immune response pathways. Three common genes (CXCL2, CXCL3, CXCL1) were identified among upregulated pathways in GEJ patients, while one common gene (IL1A) was observed in GC patients. These findings suggest a complex network of biological processes influenced by FLOT4. In-depth results, including whole-exome sequencing, methylation patterns, and miRNA profiles, will be completed and presented at the conference. Conclusion: These initial findings propose that changes in gene expression related to cellular architecture and immune response are indicative of a partial response to FLOT4 in both GEJ and GC patients. The identified genes and pathways may serve as potential biomarkers for predicting treatment outcomes. Future Directions: By the time of the conference, we anticipate including a more extensive patient cohort with complete response or no response to FLOT4, and comparative analyses with a FOLFOX treatment group. The integration of forthcoming WES, methylation, miRNA, and proteomics data will provide a more comprehensive molecular predictive model. Keywords: FLOT4 chemotherapy, gastroesophageal junction cancer, gastric cancer, predictive biomarkers, differential gene expression. Citation Format: Amira Al-Fahdi, Shoaib Al Zadjali, Ibrahim Al Haddabi, Anoopa Pullanhi, Muna Al Jabri, Aida Al Yayahee, Nada Al Shuaili, Nahad Al Mahrouqi, Mansour Al Moundhri. Predictive biomarkers for neoadjuvant FLOT4 chemotherapy response in gastroesophageal cancer: Results of multi-omics approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2523.

Abstract 6433: Anti-CD36 monoclonal antibody can sensitize the neoadjuvant chemotherapy response in PDAC by eliminating the senescent tertiary lymphatic structure

Abstract Objective: Pancreatic ductal adenocarcinoma (PDAC) is deadly and aggressive. Neoadjuvant chemotherapy (NAC) may reduce tumor volume and alter the resectability of the tumor. The efficacy of neoadjuvant chemotherapy in patients is still limited. Tertiary lymphoid structures (TLSs) develop in peripheral non-lymphoid tissues and are essential for the immune response and correlate with chemotherapy in various tumor types. However, more research is needed to determine how TLSs affect neoadjuvant chemotherapy in PDAC. We aim to determine how neoadjuvant chemotherapy affects tumor-infiltrating lymphocytes (TLSs) in PDAC patients. We also want to find a biomarker to boost PDAC neoadjuvant chemotherapy response. Methods: We retrospectively collected formalin-fixed paraffin embedded (FFPE) tissues from 115 PDAC patients without preoperative treatment and 72 patients pretreated with neoadjuvant chemotherapy. Multispectral images were processed using AI-powered image analysis software (Tissue Gnostics; Zeiss, Germany). The 10X Genomics platform was used to sequence single cells in tissue samples from five patients who received neoadjuvant chemotherapy (NAC) and five patients who had not received any treatment before analysis (pretreatment naïve, PN). TLS was separated using Laser Microdissection. The mouse model was created by orthotopically injecting tumor cells into the pancreas. Results: Patients who received NAC have a senescent microenvironment. High-throughput single-cell sequencing showed that the senescent gene signature score was enriched in the NAC group, especially in immune cells. The percentage of p16+ CD20+ B cells and P16+ CD3+ T cells in TLSs also increased in the NAC group. Spatial transcriptomics analysis exhibited that CD36 is highly expressed in senescent TLSs, which suggested that CD36 may be a marker for senescent TLSs. Moreover, CD36+ TLSs induced the infiltration of MDSCs and regulatory T cells. CD36+ TLSs were an independent prognostic factor for poor overall survival (OS) (HR=0.67, p=0.002) and progression-free survival (PFS) (HR=0.71, p=0.003). A mice orthotopic xenograft model showed that an anti-CD36 monoclonal antibody eliminated senescent TLSs in pancreatic tissue. MDSCs and Tregs in the surrounding tissue also decreased. Additionally, in vivo KPC mice model showed that the combination of an anti-CD36 and chemotherapy reduced tumor volume and increased survival compared to chemotherapy alone. Conclusion: NAC has the potential to induce the senescence of tumor-associated TLSs, a phenomenon that has been linked to unfavorable prognosis in PDAC. CD36 serves as a viable marker for senescent TLSs that can be targeted. The administration of an anti-CD36 monoclonal antibody can potentially enhance the efficacy of chemotherapy in PDAC by selectively eliminating CD36+ senescent TLSs in mouse models. Citation Format: Jingrui Yan, Tianxing Zhou, Chao Yang, Yongjie Xie, Jun Yu, Jihui Hao. Anti-CD36 monoclonal antibody can sensitize the neoadjuvant chemotherapy response in PDAC by eliminating the senescent tertiary lymphatic structure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6433.