Breast Cancer Outcomes Research Articles

The Impact of the Coexpression of MET and ESR Genes on Prognosticators and Clinical Outcomes of Breast Cancer: An Analysis for the METABRIC Dataset

Purpose. Breast cancer is a heterogeneous disease. Exploring new prognostic and therapeutic targets in patients with breast cancer is essential. This study investigated the expression of MET, ESR1, and ESR2 genes and their association with clinicopathologic characteristics and clinical outcomes in patients with breast cancer. Methods. The METABRIC dataset for breast cancer was obtained from the cBioPortal public domain. Gene expression data for MET, ESR1, and ESR2, as well as the putative copy number alterations (CNAs) for MET were retrieved. Results. The MET mRNA expression levels correlated inversely with the expression levels of ESR1 and positively with the expression levels of ESR2 (r = −0.379, p<0.001 and r = 0.066, and p=0.004, respectively). The ESR1 mRNA expression was significantly different among MET CNAs groups p<0.001. Patients with high MET/ESR1 coexpression had favorable clinicopathologic tumor characteristics and prognosticators compared to low MET/ESR1 coexpression in terms of greater age at diagnosis, reduced Nottingham Prognostic Index, lower tumor grade, hormone receptor positivity, HER2-negative status, and luminal subtype p<0.001. In contrast, patients with high MET/ESR2 coexpression had unfavorable tumor features and advanced prognosticators compared to patients with low MET/ESR2 coexpression p<0.001. No significant difference in overall survival was observed based on the MET/ESR coexpression status. However, when data were stratified based on the treatment type (chemotherapy and hormonal therapy), survival was significantly different based on the coexpression status of MET/ESR. Conclusions. Findings from our study add to the growing evidence on the potential crosstalk between MET and estrogen receptors in breast cancer. The expression of the MET/ESR genes could be a novel prognosticator and calls for future studies to evaluate the impact of combinational treatment approaches with MET inhibitors and endocrine drugs in breast cancer.

CD163+ macrophages in the triple-negative breast tumor microenvironment are associated with improved survival in the Women’s Circle of Health Study and the Women’s Circle of Health Follow-Up Study

BackgroundTumor-associated macrophages (TAMs) are a prominent immune subpopulation in the tumor microenvironment that could potentially serve as therapeutic targets for breast cancer. Thus, it is important to characterize this cell population across different tumor subtypes including patterns of association with demographic and prognostic factors, and breast cancer outcomes.MethodsWe investigated CD163+ macrophages in relation to clinicopathologic variables and breast cancer outcomes in the Women’s Circle of Health Study and Women’s Circle of Health Follow-up Study populations of predominantly Black women with breast cancer. We evaluated 611 invasive breast tumor samples (507 from Black women, 104 from White women) with immunohistochemical staining of tissue microarray slides followed by digital image analysis. Multivariable Cox proportional hazards models were used to estimate hazard ratios for overall survival (OS) and breast cancer-specific survival (BCSS) for 546 cases with available survival data (median follow-up time 9.68 years (IQR: 7.43–12.33).ResultsWomen with triple-negative breast cancer showed significantly improved OS in relation to increased levels of tumor-infiltrating CD163+ macrophages in age-adjusted (Q3 vs. Q1: HR = 0.36; 95% CI 0.16–0.83) and fully adjusted models (Q3 vs. Q1: HR = 0.30; 95% CI 0.12–0.73). A similar, but non-statistically significant, association was observed for BCSS. Macrophage infiltration in luminal and HER2+ tumors was not associated with OS or BCSS. In a multivariate regression model that adjusted for age, subtype, grade, and tumor size, there was no significant difference in CD163+ macrophage density between Black and White women (RR = 0.88; 95% CI 0.71–1.10).ConclusionsIn contrast to previous studies, we observed that higher densities of CD163+ macrophages are independently associated with improved OS and BCSS in women with invasive triple-negative breast cancer.Trial registrationNot applicable.

Effect of young age (below 40 years) on oncologic outcomes in Lebanese patients with breast cancer: a matched cohort study

BackgroundDeveloping countries have a significantly higher incidence of breast cancer in patients younger than 40 years as compared to developed countries. This study aimed to examine if young age at diagnosis is an independent prognostic factor for worse survival outcomes in breast cancer as well as the effect of age on Disease-free survival (DFS) and local recurrence free survival (LRFS) after adjusting for various tumor characteristics, local and systemic treatments.MethodsThis is a secondary analysis of prospective cohort of patients from two existing databases. We identified patients with breast cancer aged 40 years or less and we matched them to those older than 40 years. We also matched based on stage and molecular subtypes. In cohort 1, we matched at a ratio of 1:1, while in cohort 2 we matched at a ratio of 1:3.ResultsIn cohort 1, Disease-free survival (DFS) at 5 years was significantly shorter for those younger than 40 years (75.6% and 92.7% respectively; p < 0.03). On multivariate analysis, only chemotherapy was found to be significant, while age was not found to be an independent predictor of prognosis. Local recurrence free survival at 5 years was similar between both age categories. Only hormonal therapy is a significant predictor for LRFS at 5 years. In the second cohort, DFS and LRFS at 3 years were similar between those younger and those older than 40 years. On multivariate analysis, no factor including age was found to be an independent predictor of prognosis.ConclusionData in the literature is controversial on the effect of young age on breast cancer prognosis. Our findings could not demonstrate that age is an independent prognostic factor in our population. There is a need for outcomes from larger, prospective series that have longer follow-ups and more data from our region.

Impact of the COVID-19 pandemic on breast cancer patient pathways and outcomes in the United Kingdom and the Republic of Ireland - a scoping review.

The COVID-19 pandemic brought unplanned service disruption for breast cancer diagnostic, treatment and support services. This scoping review describes these changes and their impact in the UK and the Republic of Ireland based on studies published between January 2020 and August 2023. Thirty-four of 569 papers were included. Data were extracted and results thematically organized. Findings include fewer new cases; stage shift (fewer early- and more late-stage disease); and changes to healthcare organization, breast screening and treatment. Examples are accepting fewer referrals, applying stricter referral criteria and relying more on virtual consultations and multi-disciplinary meetings. Screening service programs paused during the pandemic before enacting risk-based phased restarts with longer appointment times to accommodate reduced staffing numbers and enhanced infection-control regimes. Treatments shifted from predominantly conventional to hypofractionated radiotherapy, fewer surgical procedures and increased use of bridging endocrine therapy. The long-term impact of such changes are unknown so definitive guidelines for future emergencies are not yet available. Cancer registries, with their large sample sizes and population coverage, are well placed to monitor changes to stage and survival despite difficulties obtaining definitive staging during diagnosis because surgery and pathological assessments are delayed. Multisite longitudinal studies can also provide guidance for future disaster preparedness.

Abstract ED03-03: Impact of exercise on breast cancer outcomes

Abstract Background: Exercise may improve breast cancer outcomes; however, current research is limited in its ability to inform clinical exercise trials and clinical oncology practice. The purpose of this presentation is to summarize the current research on exercise and breast cancer outcomes using a framework proposed to improve the clinical utility of this research. The Exercise as Cancer Treatment (EXACT) Framework organizes and characterizes the critical aspects of a clinical oncology setting to allow for a more systematic and clinically informative approach to the study of exercise as a cancer treatment. The EXACT Framework proposes that two key clinical oncology variables—tumor/disease status (i.e., primary tumor present, primary tumor removed, metastatic disease present) and treatment status (i.e., treatment naïve, actively being treated, previously treated)—are critical for understanding the effects of exercise on cancer outcomes, but few studies have addressed these variables. Application of the EXACT Framework to existing studies may improve their interpretation and identify directions for future research. Results: Presently, there are no adequately powered randomized controlled trials that have examined the effects of exercise on breast cancer outcomes in any clinical oncology scenario, although secondary analysis of smaller phase II trials have been reported. Preclinical research using rodent models has generally shown that exercise slows the growth and spread of treatment naïve breast tumors through various mechanisms including immune response, tumor metabolism, apoptosis, and DNA synthesis and repair. More recently, these preclinical studies have enhanced their clinical utility by including an existing cancer treatment in their design and have generally shown that exercise enhances the delivery and/or efficacy of concurrent cancer treatments through mechanisms related to improved tumor vasculature and perfusion. Most human evidence on exercise and breast cancer outcomes has been gleaned from secondary analysis of observational studies involving healthy cohorts or breast cancer survivor cohorts. These studies have generally included early-stage breast cancer patients who received heterogeneous cancer treatments. Physical activity data was typically collected either well before diagnosis and/or well after treatments. Overall, these studies have generally shown that higher prediagnosis and postdiagnosis physical activity are associated with a lower risk of breast cancer recurrence and mortality. Discussion: There is a disconnect between the clinical oncology scenarios addressed by animal and human studies of exercise and breast cancer outcomes. Moreover, most studies do not adequately address treatment combinations and sequencing. Future observational studies of exercise and breast cancer outcomes may improve their clinical utility by: (a) recruiting breast cancer patients with the same tumor/disease status receiving the same or similar first-line treatment protocols, (b) collecting detailed data on all planned and unplanned cancer treatments, (c) assessing exercise in relation to those cancer treatments (i.e., before, during, between, after) rather than in relation to the cancer diagnosis (i.e., various time periods before and after diagnosis), (d) collecting data on cancer-specific outcomes (e.g., disease response, progression, recurrence) in addition to mortality, and (e) conducting subgroup analyses based on cancer treatments received. Conclusions: Preclinical and observational studies may contribute important knowledge regarding the role of exercise as a cancer treatment; however, modifications to study design and analysis are necessary if they are to inform clinical research and practice. The ultimate goal of precision exercise oncology is to provide the right exercise prescription to the right breast cancer patient at the right time postdiagnosis. Citation Format: K. Courneya. Impact of exercise on breast cancer outcomes [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 ED03-03.

Abstract PO3-10-03: Nationwide Impact of Neighborhood Poverty Hotspots on Breast Cancer Mortality

Abstract Title: Nationwide Impact of Neighborhood Poverty Hotspots on Breast Cancer Mortality Background: Poverty is known to lead to the worst breast cancer (BC) outcomes, at the individual and county level. However, we believe that the relationship between poverty and breast cancer mortality is more complex and can be influenced by the economic status and available resources of the surrounding neighborhoods. Our goal is to understand to what extent poverty in the surrounding neighborhood may contribute to breast cancer mortality on a national scale and the county areas at the highest risk. Methods: This study examines the association between neighborhood effects of poverty on overall and BC mortality among women diagnosed between 2005 and 2019 from NCI SEER. We also obtained county-level five-year poverty estimates from the American Community Survey. Counties with poverty estimates above or below the national mean were high-poverty (H) or low-poverty (L) counties, respectively. We then used local indicators of spatial autocorrelation (LISA) analysis with Local Moran’s I of the poverty estimates and their H- and L-county categorization to define four neighborhood poverty environments for US counties. Specifically, H-counties among other H-counties were classified as poverty hotspots (HH) counties, L-counties among other L-counties were classified as poverty cold spots (LL), H-counties among LL-counties were HL-counties, and L-counties among HH-counties were LH-counties. Non-Hispanic White (NHW), Non-Hispanic Black, and Hispanic women at least 20 years of age diagnosed with local, regional, or distal stage BC between 2005-2009 and 2010-2014 that survived more than one year after diagnosis were aggregated by county of residence at diagnosis to determine their neighborhood poverty environment at BC diagnosis. Women included in the study had a Local Moran's I p-value less than or equal to 0.3 for their county of residence. A Poisson regression model that adjusts for age at diagnosis, race/ethnicity (NHW vs. not-NHW), BC stage, year of diagnosis (2005-2009 vs. 2010-2014), both local and systemic treatment except for hormone therapy, and Estrogen Receptor (ER) status (negative vs. positive) was used to assess the effects of county-level poverty cluster types on BC mortality. Results: Our analysis includes 24,070 women diagnosed with BC, of which 6,919 women died, and 2,262 of these deaths were specific to BC. In total, 4,528 women were in HH counties from CA, GA, KY, LA, NM, UT, and HI; 14,112 women were in LL counties; 4,338 women were in HL counties; 1,092 women were in LH counties. Women in HH, LH, and HL counties had a 1.28 (95%CI:1.15,1.42), 1.23 [95%CI:1.01-1.48], and 1.05 [CI: 0.93,1.17] relative risk of cause-specific BC death respectively when compared to deaths in LL counties after adjustment for year of diagnosis, age at diagnosis, race/ethnicity, stage at diagnosis, treatment, and estrogen receptor status. When stratified by ER status or BC stage at diagnosis, the relative risk of BC mortality for women in HH counties diagnosed with ER-positive, local or regional stage had a 1.35 (95% CI: 1.19,1.52), 1.32 (95%CI: 1.13,1.54), and a 1.21 (95%CI:1.02,1.43) when compared to women in LL counties, respectively. Our analysis also showed that total death trends were similar to the trends observed in cause-specific deaths. In addition, we observed similar total and cause-specific BC death trends when using a p-value of 0.05 for the LISA analysis. Conclusion: We use LISA spatial clustering to demonstrate the impact national poverty neighborhood environments have on BC mortality, thus identifying counties of worst BC outcomes through neighborhood poverty environments. Our findings suggest that prioritization of resource allocations to HH counties would significantly improve BC outcomes. Citation Format: Ifeoma Nwigwe, Michael Desjardins, Kala Visvanathan. Nationwide Impact of Neighborhood Poverty Hotspots on Breast Cancer Mortality [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 PO3-10-03.

Abstract PO4-09-09: Deep Immunoprofiling Demonstrates Racial Differences in the Peripheral Immune System in Women at Risk for Breast Cancer

Abstract Background: Disparities in breast cancer outcomes between Non-Hispanic Black (NHB) and Non-Hispanic White (NHW) women have been attributed to NHB women presenting with more aggressive subtypes and later stage disease, differences in treatment receipt and adherence, access to care and tumor biology. However, previous work has shown that these known factors do not fully account for the observed disparities in outcomes. Systemic immune fitness is a factor not previously studied that may play a role in dictating disease progression and therapeutic responses. Numerous factors, including age and race, impact immune system function and understanding these changes is critical to address disparities in breast cancer outcomes. Here, we developed a pipeline for deep immunoprofiling of peripheral blood mononuclear cells (PBMC) at single cell resolution by full-spectrum flow cytometry. Using this pipeline, we sought to investigate whether there are differences in immune fitness between NHB and NHW women at high risk for developing breast cancer. Methods: PBMC were collected and processed from age-matched NHB and NHW women (n=20/cohort) identified as being at high risk for developing breast cancer through our institution’s B-PREP (Breast Cancer Personalized Risk Assessment Education and Prevention) clinic. Two custom antibody panels and protocols for comprehensive immunoprofiling of T and B cell subsets (T/B Panel), as well as monocytic, NK, and dendritic cell subsets (M/N/D Panel), along with functional and exhaustion markers were designed, optimized, and implemented. Traditional gating strategies were used to quantify proportions of canonical cell populations, and unbiased high dimensionality reduction analysis was performed using the OMIQ analysis platform to assess phenotypes and functional status of various immune cell subsets. Results: Significant differences between cohorts in abundance as well as phenotype of various cell populations were observed. Specifically, CD4+ follicular helper T cells, TEMRA CD8, and CD45RA Terminal Effector CD8+ cells were enriched in NHB women while PD-1+/CD3+ cells and PD-1+/CD8+ cells were enriched in the NHW women (Table). Additionally, several immunosuppressive and systemic inflammatory immune cell types were enriched in NHB women (Table). Conclusions: Deep immunoprofiling using single-cell spectral flow cytometry revealed differences in peripheral immune cells between NHB and NHW women at high risk for breast cancer. The significant enrichment of immunosuppressive monocytes and several activated NK cell populations in PBMC samples from NHB women relative to those from NHW women indicate an altered immune environment that may influence breast cancer development. Additional analysis, including a larger sample size and patients with invasive cancer, are ongoing to further understand if differences in immune fitness between NHB and NHW women are associated with disparities in breast cancer outcomes. Table: PBMC populations (% of CD45+) that are significantly enriched in NHB relative to NHW patients Citation Format: Esther Ogayo, Milos Spasic, Tasnim Rahman, Olga Kantor, Tari King, Peter van Galen, Sandra McAllister, Elizabeth Mittendorf. Deep Immunoprofiling Demonstrates Racial Differences in the Peripheral Immune System in Women at Risk for 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 PO4-09-09.

Abstract PO2-11-02: Incidence, treatment patterns and outcomes of breast cancer during the first year of the COVID pandemic: A population-based study

Abstract Background: The COVID pandemic created significant challenges in breast cancer (BC) care which were most pronounced during 2020 when screening and treatment access were reduced. The aims of this study were to evaluate and compare the incidence of BC, treatment patterns, and outcomes during the year 2020 versus the immediate pre-pandemic (2018 and 2019) period. Methods: Using data from the Surveillance, Epidemiology, and End Results (SEER) program, we calculated age-adjusted incidence rates of ductal carcinoma in situ (DCIS) and invasive BC during 2018, 2019 and 2020, with a 95% confidence interval (CI) for each. In the invasive BC cohort, we compared chemotherapy and radiation utilization by year. To account for potential misclassification of cause of death (COD) during the pandemic, we evaluated outcomes by overall survival (OS) in the invasive cohort, defined as time from BC diagnosis until death from any cause. To assess the impact of COVID, OS was truncated at 12 months from diagnosis for each year and we compared OS at 12 months for patients (pts) diagnosed with invasive BC in 2020 versus 2018 and 2019. OS was compared in a multivariable Cox model with diagnosis year 2020 as the reference. The Cox model was adjusted for age at diagnosis, race and ethnicity, sex, tumor grade, histology, stage, tumor subtype, surgery, radiation, chemotherapy, marital status, median household income, and rurality. Results: There were 37,834 DCIS diagnoses, and 199,594 invasive BC diagnoses between 2018-2020, with the distribution by year shown in the table. In 2020, the age-adjusted incidence of female DCIS decreased to 31.0 cases per 100,000, and the age-adjusted incidence of female invasive BC decreased to 166.6 cases per 100,000. As shown in the table, the incidence of male BC did not change. Among females, the relative reductions in incidence from 2019 to 2020 were: 15% for DCIS, 12% for stage I, 6% for stage II, 3% for stage III, and 2% for stage IV. Comparing 2020 to 2018-2019, we observed small absolute decreases in the proportions of pts who had surgery (2%) or radiation therapy (2.8%), and a small absolute increase in chemotherapy (1.4%) (p&amp;lt; 0.001 for each). These treatment changes were present across each individual stage. The table shows the 12-month OS rates for each year of diagnosis. COVID was the COD for 77 pts in 2020, 43 pts in 2019 and 0 pts in 2018. In the Cox model, there were no significant differences in the risk of death between pts diagnosed 2018 and 2020 (adjusted Hazard Ratio: 0.95; 95% CI, 0.90 – 1.01; p=0.13) or between pts diagnosed 2019 and 2020 (adjusted Hazard Ratio: 0.95; 95% CI, 0.89 – 1.01; p=0.08). Conclusions: During the first year of the pandemic, the incidence of BC decreased significantly, largely driven by a decrease in DCIS and early-stage diagnoses. Of interest, there was no stage shift observed with respect to the incidence of stage III or de novo stage IV disease, and no change in male BC incidence. We hypothesize that the observed trends are due to a reduction in screening, but this needs further study. It will be critical to evaluate future trends in cancer incidence beyond 2020, as it is possible that the reduction in early-stage diagnoses represent missed diagnoses that will be identified at a later stage in subsequent years. Finally, while there was no difference in 12-month OS by year of diagnosis, the true impact of the COVID pandemic on BC-specific outcomes will require further follow-up. Citation Format: Jose Leone, Julieta Leone, Michael Hassett, Rachel Freedman, Jorge Avila, Carlos Vallejo, Nabihah Tayob, Sara Tolaney, Nancy Lin. Incidence, treatment patterns and outcomes of breast cancer during the first year of the COVID pandemic: A population-based 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 PO2-11-02.

Abstract PO5-09-06: Outcomes of breast cancer in a minority-enriched population treated at a large safety-net system: Is site of care a predictor of poor outcomes?

Abstract Background: Breast cancer outcomes in the United States continue to improve, but sociodemographic disparities remain prevalent and impact care delivery and outcomes in vulnerable populations. Safety-net health systems are intended to address inequities by providing access to care for the uninsured/underinsured. Care delivery in a safety-net setting is often inherently complicated by limited resources at these institutions. Here, we present the overall survival (OS) data of breast cancer patients treated at a large safety-net system, compared to the national average. Methods: Parkland Health (PH) is the safety-net system for Dallas County and is affiliated with the University of Texas Southwestern Harold C. Simmons Comprehensive Cancer Center (NCI-CCC). Electronic medical records of patients diagnosed with invasive breast cancer between 2018 to 2020 at PH were reviewed and data on demographics, treatment, and outcomes were collected. Categorical data was summarized with counts and percentages and continuous data was summarized with median and interquartile range. Statistical comparisons used Chi-square test for categorical data and rank sum test for continuous data with a significance level of 0.05. Survival data was analyzed using Cox proportional hazard model. Data from the National Cancer Database (NCDB) for the same period was used for comparison. Results: Of the 657 patients included in the study, the majority (82.5%) belonged to racial and ethnic minorities (Hispanic 50.2%; Black 32.3%). Compared to the NCDB, PH patients were more often uninsured (67% vs 1.6%) or enrolled on Medicaid (14.5% vs 6.9%), and less often on Medicare (8.5% v. 43%) (p&amp;lt; 0.01). Triple negative breast cancer (TNBC) phenotype and late-stage diagnosis (stage III/IV) rates were higher at PH compared to NCDB (TNBC 22.8% vs 10.7%, p&amp;lt; 0.01; late stage 30.6% vs 13.2%, p&amp;lt; 0.01). At a median follow up of 33 (range 24-43) months in PH and 28 (range 21-36) months in NCDB, the unadjusted OS for the PH population was 86.3% vs 92.6% for the NCDB population (p &amp;lt; 0.01). Within the PH population, Black race, higher stage, and TNBC were associated with decreased OS. There was a significant interaction between Black race and TNBC. When combining all patients (PH+NCDB), site of care (PH) was associated with a higher risk of death from breast cancer (HR 1.467, 95% CI 1.192-1.805, p&amp;lt; 0.0005), however, multivariate analysis did not show a significant difference based on site of care. Factors associated with a significantly increased risk of death in this multivariate analysis (corrected for interaction between Black race and TNBC phenotype) included age, late-stage diagnosis, TNBC, Black race, and uninsured status (Table 1). Conclusions: Breast cancer patients treated at PH were more likely to have adverse disease characteristics compared to the NCDB population. When accounting for these risk factors in multivariate analysis, patients treated at PH had similar outcomes compared to the national average. Our findings reinforce the critical role of safety-net systems in promoting health equity and eliminating disparities. Table 1 Citation Format: Sarah Kashanian, Shifa Kanjwal, L. Steven Brown, Andrea Semlow, Mary Hodges, Robyn Cobb, Brad Walsh, Umber Dickerson, Navid Sadeghi. Outcomes of breast cancer in a minority-enriched population treated at a large safety-net system: Is site of care a predictor of poor outcomes? [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 PO5-09-06.

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

Abstract Background: Stromal tumor-infiltrating lymphocytes (sTILs) quantification is associated with pathological response to neoadjuvant chemotherapy (NAC) and long term outcomes in setting of adjuvant anthracycline based chemotherapy. A previous study in TNBC patients treated with adjuvant anthracycline chemotherapy shows that at a cut point of 30%, sTILs can up and downstage traditional AJCC stage groups. Additive impact of sTILs on refining outcomes beyond pathological response and TNM stage for patients treated with anthracycline-free chemotherapy is not known. This study aimed to investigate impact of sTILs on outcomes in a large cohort of TNBC patients treated with Docetaxel plus carboplatin NAC. Methods: Patients with stage I (T size &amp;gt; 1cm) to III TNBC scheduled to receive 6 cycles of NAC docetaxel (75 mg/m2) plus carboplatin (AUC 6) (TCb) every 3 weeks from two studies (NCT01560663 and NCT02302742) were combined for this analysis. sTILs were evaluated on pre-treatment H&amp;E slide using standard criteria centrally by one of the investigators (RS). Pathological complete response (pCR) was defined as ypT0/is ypN0. Logistic regression analysis was used to examine the effect of multiple variables on Event free survival (EFS) and overall survival (OS). Results: For 474 patients included in this analysis, median age was 52 years, 8% were Black, 13% had germline BRCA1/2 mutation, 44% had clinical Lymph node (LN) positive disease and 13%, 62% and 25% respectively had TNM stage I, II and III disease. Median sTILs were 5% (range 1-95%) and 25% had &amp;gt;30% sTILs. pCR and RCB 0+1 rates were 50.2% and 60.4% respectively. On multivariable analysis, T stage (OR=0.51, p=0.030), nodal status (OR=0.56, p=0.028), Ki67 (OR=2.74, p&amp;lt; 0.001) and sTILs (OR=2.01, p=0.014) were associated with pCR. pCR rate in those with sTILs &amp;lt; 30 vs sTILs &amp;gt;30 was 45.9% and 63.9% respectively (p=0.0014). At median follow-up of 58 months, 5 years EFS was 81.05% in all patients, 93.94% in those with pCR and 68.67% in those without pCR, 5 year OS was 84.83% in all patients, 96.53% in those with pCR and 74.13% in those with residual disease. On multivariate analysis lower T stage, negative LN status and increasing sTILS were associated with better EFS (T stage: HR =1.98, p=0.018; LN status: HR=2.92, p&amp;lt; 0.001; sTILs: HR:0.46, p=0.04) and OS (T stage: HR=1.89, p=0.040; LN status: HR=3.13, p=0.001; sTILs: HR=0.30, p=0.008). At a cut-point of 30%, sTILs up and downstaged anatomic AJCC TNM stage groups (table 1). Conclusions and Relevance: In patients treated with anthracycline-free TCb chemotherapy, sTILs were independent predictors of EFS and OS beyond clinicopathological features. Notably, 30% sTILs cut-point stratified outcomes beyond anatomical TNM staging. These, findings can aid in patient stratification for chemotherapy backbone de-escalation in future trials and have the potential to inform patient selection for adjuvant treatment escalation and de-escalation trials. Tumor infiltrating lymphocyte stratification refines AJCC TNM staging based outcomes of early-stage triple negative breast cancer treated with neoadjuvant anthracycline-free, docetaxel and carboplatin chemotherapy. Table. Citation Format: Miguel Martín, Rachel Yoder, Roberto Salgado, María del Monte-Millán, Enrique Álvarez, Isabel Echavarria, Joshua Staley, Coralia Bueno-Muiño, Yolanda Jerez Gilarranz, Andrew Godwin, María Cebollero, Oscar Bueno, José Ángel García-Sáenz, Fernando Moreno Antón, Uriel Bohn, Henry L Gómez, Tatiana Massarrah, Sara López-Tarruella, Priyanka Sharma. Tumor infiltrating lymphocyte stratification refines AJCC TNM staging based outcomes of early-stage triple negative breast cancer treated with neoadjuvant anthracycline-free, docetaxel and carboplatin chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS16-07.

Abstract PO4-22-08: Ten-Year Oncologic Outcomes in T1-3N1 Breast Cancer After Targeted Axillary Sampling: A Retrospective Study

Abstract Background Targeted axillary sampling (TAS) is a new surgical concept for the assessment of axillary lymph node status in breast cancer that is hypothesized to be more effective at minimizing postoperative morbidities than axillary lymph node dissection (ALND), provided the metastatic axillary lymph node can be accurately detected without missing data; however, the oncologic outcomes over long-term follow-up have not been sufficiently investigated. This was a retrospective analysis to evaluate the 10-year oncologic outcomes in T1-3N1 breast cancer after TAS. Methods Clinically, we defined TAS as removal of a bunch of ALNs located around SLNs and targeted LNs, but without full exposure of the axillary vein, long thoracic nerve and thoracodorsal nerve. Between 2008 and 2013, 230 female patients with cT1-3N1 breast cancer underwent breast and axillary surgery (ALND, n = 171; TAS, n = 59) at our institute. After TAS was applied, additional axillary radiotherapy was performed. Various postoperative complications, including postoperative seroma, lymphedema, and 10-year oncological outcomes, were evaluated and compared between the ALND and TAS groups. Results Although overall survival during the 10-year follow-up period was better in the TAS group, there was no statistically significant difference in oncologic outcomes, including locoregional recurrence, distant metastasis, and overall survival (p = 0.395, 0.818, and 0.555, respectively). Furthermore, the incidence of lymphedema on the ipsilateral arm was significantly higher in the ALND group (p &amp;lt; 0.001). Conclusions The 10-year oncological outcomes of TAS were not inferior to those of conventional ALND in T1-3N1 breast cancers; however, the incidence of lymphedema was significantly higher in the ALND group. Citation Format: Byeongju Kang, Jeeyeon Lee, Yee Soo Chae, Ho Yong PARK, Jin Hyang Jung. Ten-Year Oncologic Outcomes in T1-3N1 Breast Cancer After Targeted Axillary Sampling: A Retrospective 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 PO4-22-08.

Abstract PO1-03-07: Revisiting the potential of pathological complete response as a surrogate for long-term survival outcomes in triple-negative breast cancer at the trial-level

Abstract Background: Pathological complete response (pCR) has been used as a primary endpoint in neoadjuvant clinical trials for non-metastatic breast cancer and as a surrogate endpoint for long-term survival outcomes. The U.S. Food and Drug Administration (FDA) accepted pCR as a surrogate endpoint for the approval of new drugs in the neoadjuvant setting in high-risk early-stage breast cancer. However, though the Collaborative Trials in Neoadjuvant Breast Cancer (CTNeoBC) pooled analysis in 2014 showed that at the patient level achieving pCR was associated with longer overall survival (OS) and event-free survival (EFS), at the trial-level the association between high pCR rate and better OS and EFS outcomes was weak (coefficient of difference [R2]; 0.03 and 0.24, respectively) among all subtypes of breast cancer. A recent study reported that this association at the trial-level was similarly weak among Human Epidermal Growth Factor Receptor-2 (HER-2) positive breast cancer (R2; 0.02 and 0.23, respectively). However, the potential surrogacy of pCR rate for OS and EFS in triple-negative breast cancer (TNBC) in the neoadjuvant setting has not been well studied in a comprehensive manner. Moreover, because of significant advances in systemic treatment strategies in TNBC over the past decade including a combination of immune checkpoint inhibitors (ICIs) with conventional cytotoxic agents, the trial-level surrogacy needs to be reassessed in recently published neoadjuvant clinical trials for TNBC. Our primary objective is to assess the association between pCR rate and survival outcomes in neoadjuvant clinical trials for TNBC by collecting data from articles published after the CTNeoBC article in 2014. Methods: We performed a systematic literature search based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in the PubMed, Cochrane Library, and Web of Science databases. Articles published between January 1, 2014, and March 31, 2023, were searched. We included only randomized control trials of neoadjuvant treatments for clinical stage I-III TNBC that compared two or more regimens followed by curative intent breast surgery. The selected trials had data for odds ratio (OR) for pCR and hazard ratios (HRs) either for OS or for EFS or disease-free survival (DFS). We excluded trials including estrogen receptor positive, progesterone receptor-positive, or HER-2 positive diseases, and those without data enough to obtain ORs for pCR, HRs for OS, EFS, or DFS. Unpublished data as a full article was also excluded. If EFS could not be obtained from the articles, DFS was used in place of EFS. Two independent investigators (TY and TF) searched and extracted data. Any disagreement was resolved by discussion with the third author (ZZ). A linear regression model on a logarithmic scale weighted by the sample size of each trial was performed and the R2 was used to assess the trial-level association between OR for pCR and HRs for OS or EFS. Results: We identified eight trials with a total of 2,926 patients. Three of the eight trials used ICIs in the intervention arm. One trial did not provide OS data and was not included in the OS analysis. In four trials, EFS was not available and DFS was used for EFS analysis. The R2 was 0.191 (95% confidence interval [CI], 0.165 to 0.218) for OS and 0.193 (95% CI, 0.167 to 0.219) for EFS. Conclusions: Similarly to the previous reports, our findings suggest that the surrogacy of the pCR rate for OS and EFS in recent neoadjuvant clinical trials for TNBC is weak. At this moment, there is no strong evidence to support using pCR as a surrogate for long-term survival outcomes in neoadjuvant clinical trials for TNBC. Citation Format: Toru Yoshino, Zao Zhang, Ryota Sato, Stanley Lipkowitz, Takeo Fujii. Revisiting the potential of pathological complete response as a surrogate for long-term survival outcomes in triple-negative breast cancer at the trial-level [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-03-07.

Abstract PO4-05-01: Clinical outcomes of breast cancer and its relationship with access to health care in Brazil: prospective study in HER2 negative/hormone receptor positive metastatic disease - BREAST (BRazilian outcomE for metAStatic breasT cancer)

Abstract Background: Cancer survival is one of the key measures of the effectiveness of cancer services and captures whether people have access to effective treatment. The survival rate of breast cancer in low and middle-income countries is notably different from high-income countries; this disparity in survival reflects limited access to first-line systemic therapy for advanced and metastatic tumors. Recent studies have shown benefit of combining cyclin-dependent kinase 4 and 6 inhibitors (CDK 4/6) with endocrine therapies in hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced or metastatic breast cancer. However, in Brazil, the population has limited access to these drugs, mainly in the public health service. The commercialization of CDK 4/6 inhibitors was only released in the national territory in 2018, but until nowadays it is not accessible for most patients. Objective: The aim of this project is to assess whether patients without private health insurance may experience worse outcomes compared to women with private insurance, primarily due to limited access to a specific class of medication during their treatments. The study seeks to gain insights into the clinical outcomes of patients with HR+ HER2- metastatic breast cancer based on their access to health insurance coverage within a real-world setting. Methods: Multicenter, prospective observational study, with patients divided into two groups: one with patients from the public health system and the second with patients treated at the private service. Whereas that the hazard ratio for the primary outcome in the private system compared to the public health system is like that observed in the PALOMA study (0.58), and that event rates after 18 months of follow-up are also similar (approximately 45% and 35%), then a total of 298 patients will provide the study power of 80%, significance level of 5%. This calculation considers a sample size ratio of 1 patient in the private health system for every 2 patients in the public health system. The inclusion criteria specify women with HR+ HER2- metastatic breast cancer who initiated first-line treatment from 2019. Patients will be followed for 24 months and stratified based on the use or non-use of CDK 4/6 inhibitors. The study was approved by the local ethics committee and registered with Clinical Trials (NCT05559528). Results: A total of 300 patients were evaluated, with 199 (66.3%) in the public health system and 101 (33.7%) in the private service. The mean age was 58 years, and 76.2% were postmenopausal. In terms of metastasis site, 84.7% had non-visceral disease, predominantly with bone metastasis (75.7%), which is an expected characteristic of this type of tumor. The use of CDK 4/6 inhibitors at any point in the treatment of metastatic disease was 7.0% in the public health system versus 90.1% in the private service. As a preliminary outcome, with a median time since the diagnosis of metastatic breast cancer of 22.8 months, a mortality rate of 10% was identified in the public health system group compared to 5% in the private service group. Conclusions: The results of our study highlight the disparity in the treatment of metastatic breast cancer among patients in relation to access to healthcare. Patients dependent on the public health system experience higher mortality rates. These findings are crucial for supporting discussions on improving local policies regarding access to medications that have been proven to enhance the prognosis of these patients. Citation Format: Vanessa Sanvido, Lucíola Pontes, Rachel Machado, Marina Nicola, Jackeline Gomes, Letícia Barbante, Nanci Valeis, Alexandre Cavalcanti, Afonso Nazário. Clinical outcomes of breast cancer and its relationship with access to health care in Brazil: prospective study in HER2 negative/hormone receptor positive metastatic disease - BREAST (BRazilian outcomE for metAStatic 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 PO4-05-01.

Abstract PO1-28-09: Rethinking the value of pathologic complete response rate for the survival outcomes of early triple-negative breast cancer treated with neoadjuvant chemotherapy: a systematic review and network meta-analysis

Abstract Background: Neoadjuvant chemotherapy (NACT) has been more frequently used in breast cancer, but it’s controversial whether NACT or adjuvant chemotherapy (ACT) is more effective in improving survival outcomes for triple-negative breast cancer (TNBC) patients. Recent studies also proposed pathologic complete response (pCR) could not be a robust surrogate for survival outcomes in certain types of breast cancer. To address these questions, a general meta-analysis and a network meta-analysis (NMA) were conducted to compare the survival outcomes of patients with pCR, non-pCR after NACT and ACT. The cut-off pCR rate was also declared to indicate when NACT produces equivalent survival outcomes to ACT (Registration: PROSPERO CRD42022336732). Methods: Databases including PubMed, Embase, Web of science and Cochrane library were searched up to June 2023 to investigate studies comparing NACT and ACT, as well as randomized controlled trials (RCTs) comparing different regimens in NACT or ACT settings in early operable TNBC patients. Heterogeneity was assessed using χ² based Q-test and I², combined with hazard ratios (HRs) with 95% confidence intervals (CI) computed for overall survival (OS), and disease-free survival (DFS, or event-free survival). The NMA with a Bayesian framework was conducted using both random and fixed effect model. The Weighted Least Square method and the Least Absolutely Deviation method were used to determine the cut-off pCR rates of OS and DFS. Results: A total of 35 studies involving 21 RCTs and 34143 TNBC patients were included. The general meta-analysis comprised 14 cohort studies. Eight high-quality cohort studies with propensity score matching and 21 RCTs were included in NMA. The pooled pCR rate for NACT was 42.2% (95% CI 37.8%-46.8%). Overall, the NACT cohort showed significantly worse OS and DFS than ACT cohort (HR=1.67, 95% CI 1.22-2.31; HR=1.37, 95% CI 1.14-1.64). However, patients with pCR after NACT showed improved OS than ACT (HR=0.58, 95% CI 0.50-0.66), while the patients without pCR after NACT had pooper OS than ACT (HR=2.03, 95% CI 1.88-2.19). As for DFS, there was no statistically difference between pCR after NACT and ACT groups (HR=1.04, 95% CI 0.63-1.73), while patients without pCR after NACT had significantly worse DFS than ACT (HR=2.65, 95% CI 1.98-3.55). From the NMA, the OS and DFS were better when combining modern target therapy such as Bevacizumab, PARPi, and PD-1/PD-L1 inhibitor (Figure 1), but not achieving pCR completely negated the benefits of newer drugs. Adding adjuvant capecitabine to patients not achieving pCR seemed to favor the OS. It was predicted that when the pCR rates were 64.7% and 46.9% (Figure 2), respectively, the OS and DFS of patients treated with NACT would be the same as those of patients treated with ACT. Conclusions: Higher pCR rate after NACT was associated with improved OS compared with ACT in TNBC patients. However, failure to achieve pCR after NACT resulted in worse survival outcomes than ACT. NACT had similar survival outcomes with ACT only when the pCR rate was at least 46.9%. The development of effective NACT regimens is beneficial for breast cancer patients. Figure 1. Forest plot of the Hazard Ratio for OS and DFS in TNBC patients pCR: pathological complete response; Bev: Bevacizumab; Pt: platinum; NACT: neoadjuvant chemotherapy; ACT: adjuvant chemotherapy; vel: veliparib; PDi:PD1/PDL1 inhibitor; X: capecitabine Figure 2. The cut-off value of pCR when NACT and ACT have the same Hazard Ratio based on OS and DFS. pCR: pathological complete response; Bev: Bevacizumab; Pt: platinum; NACT: neoadjuvant chemotherapy; ACT: adjuvant chemotherapy Citation Format: Xiaoying Qiao, Shu Wang, Taobo Hu, Baosheng Liang. Rethinking the value of pathologic complete response rate for the survival outcomes of early triple-negative breast cancer treated with neoadjuvant chemotherapy: a systematic review and network meta-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 PO1-28-09.

Abstract PS16-08: Histologic Pattern and Outcomes in High-Grade Metaplastic Breast Cancer Compared to Triple-Negative Ductal Breast Cancer Counterparts: A Single Institution Retrospective Study

Abstract Background Metaplastic breast cancer (MpBC) is a rare and aggressive subtype of breast cancer that presents with high tumor stage and a poor prognosis. MpBC tumors tend to have worse outcomes compared to other non-metaplastic triple-negative breast cancers (TNBC). Although MpBC has been described as chemotherapy resistant, chemotherapy remains a mainstay of treatment. MpBC tumors can be further characterized by their specific histologic pattern. The existing literature on outcomes of MpBC by histologic pattern is limited, with varying results regarding response rate and overall survival (OS). Identifying a pattern of MpBC that has better response to treatment could help tailor treatment recommendations. Methods A retrospective chart review was performed and identified 106 patients with early-stage, high-grade MpBC who were diagnosed at Levine Cancer Institute between January 1, 2010 and September 1, 2021. A matched control cohort (n=106) of patients diagnosed with non-metaplastic TNBC was selected based on propensity score matching on diagnosis date, age at diagnosis, race, pathologic staging, and tumor grade. Patient demographics, tumor characteristics, therapeutic interventions, residual cancer burden (RCB), and outcomes were collected. The associations between the histologic patterns of MpBC and disease characteristics were evaluated using chi-squared tests for categorical variables and Wilcoxon tests for continuous variables. We also examined the differences in RCB scores between the MpBC cohort and the non-metaplastic TNBC cohort who received neoadjuvant chemotherapy. Additionally, Kaplan-Meier and Cox proportional hazard analysis was performed to assess differences in recurrence free survival (RFS) and OS between the spindle cell/sarcomatous pattern versus all other patterns. Results For the entire group (n=212), median age at diagnosis was 58 years (range, 24-92); all patients were female; 66% White, 29% Black, and 5% unknown race. Most tumors were triple-negative (91%); 19%, 56% and 14% with Clinical Stage I, II, and III disease, respectively. A total of 63% of patients underwent radiation treatment and 76% received chemotherapy (43% neoadjuvant and 57% adjuvant). Recurrence after treatment occurred in 16% of all patients. In the MpBC cohort (n=106), the histologic patterns included spindle cell/sarcomatous (34%), squamous (17%), heterologous mesenchymal (31%), mixed (17%), and other (1%). Of those with MpBC who received neoadjuvant chemotherapy (n=32), RCB among the different histologic patterns was assessed. When comparing spindle cell/sarcomatous versus the other histologic patterns combined, there was no significant difference in RCB (p = 0.81), although more RCB III scores were recorded in the spindle cell/sarcomatous pattern compared to the other MpBC patterns (40% versus 30%). When assessing RFS and OS by histologic pattern in the entire MpBC cohort, spindle cell/sarcomatous tumors had inferior RFS (p = 0.0194) and OS (p = 0.0039) compared to the other MpBC patterns combined. When comparing RCB values between MpBC and non-metaplastic TNBC, there were numerically more RCB-III classes in the MpBC cohort as compared to the non-metaplastic TNBC. Conclusion MpBC is an aggressive and difficult breast malignancy to treat. Based on our single institution review, no correlation between RCB and the histologic pattern of MpBC was found, however, RFS and OS were worse among the spindle cell/sarcomatous pattern. Furthermore, the MpBC cohort had numerically higher RCB-III scores than the TNBC control cohort, which is in line with historical data. Citation Format: Ashley Matusz-Fisher, Annabel Chen, Erin Donahue, Courtney Schepel, Michelle Wallander, Chad Livasy, Richard White, Antoinette Tan, Lejla Hadzikadic-Gusic. Histologic Pattern and Outcomes in High-Grade Metaplastic Breast Cancer Compared to Triple-Negative Ductal Breast Cancer Counterparts: A Single Institution Retrospective 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 PS16-08.

Abstract PO5-03-05: Rethinking the value of pathologic complete response rate for the survival outcomes of early triple-negative breast cancer treated with neoadjuvant chemotherapy: a systematic review and network meta-analysis

Abstract Background: Neoadjuvant chemotherapy (NACT) has been more frequently used in breast cancer, but it’s controversial whether NACT or adjuvant chemotherapy (ACT) is more effective in improving survival outcomes for triple-negative breast cancer (TNBC) patients. Recent studies also proposed pathologic complete response (pCR) could not be a robust surrogate for survival outcomes in certain types of breast cancer. To address these questions, a general meta-analysis and a network meta-analysis (NMA) were conducted to compare the survival outcomes of patients with pCR, non-pCR after NACT and ACT. The cut-off pCR rate was also declared to indicate when NACT produces equivalent survival outcomes to ACT (Registration: PROSPERO CRD42022336732). Methods: Databases including PubMed, Embase, Web of science and Cochrane library were searched up to June 2023 to investigate studies comparing NACT and ACT, as well as randomized controlled trials (RCTs) comparing different regimens in NACT or ACT settingsin early operable TNBC patients. Heterogeneity was assessed using χ² based Q-test and I², combined with hazard ratios (HRs) with 95% confidence intervals (CI) computed for overall survival (OS), and disease-free survival (DFS, or event-free survival). The NMA with a Bayesian framework was conducted using both random and fixed effect model. The Weighted Least Square method and the Least Absolutely Deviation method were used to determine the cut-off pCR rates of OS and DFS. Results: A total of 35 studies involving 21 RCTs and 34143 TNBC patients were included. The general meta-analysis comprised 14 cohort studies. Eight high-quality cohort studies with propensity score matching and 21 RCTs were included in NMA. The pooled pCR rate for NACT was 42.2% (95% CI 37.8%-46.8%). Overall, the NACT cohort showed significantly worse OS and DFS than ACT cohort (HR=1.67, 95% CI 1.22-2.31; HR=1.37, 95% CI 1.14-1.64). However, patients with pCR after NACT showed improved OS than ACT (HR=0.58, 95% CI 0.50-0.66), while the patients without pCR after NACT had pooper OS than ACT (HR=2.03, 95% CI 1.88-2.19). As for DFS, there was no statistically difference between pCR after NACT and ACT groups (HR=1.04, 95% CI 0.63-1.73), while patients without pCR after NACT had significantly worse DFS than ACT (HR=2.65, 95% CI 1.98-3.55). From the NMA, the OS and DFS were better when combining modern target therapy such as Bevacizumab, PARPi, and PD-1/PD-L1 inhibitor, but not achieving pCR completely negated the benefits of newer drugs. Adding adjuvant capecitabine to patients not achieving pCR seemed to favor the OS. It was predicted that when the pCR rates were 64.7% and 44.6%, respectively, the OS and DFS of patients treated with NACT would be the same as those of patients treated with ACT. Conclusions: Higher pCR rate after NACT was associated with improved OS compared with ACT in TNBC patients. However, failure to achieve pCR after NACT resulted in worse survival outcomes than ACT. NACT had similar survival outcomes with ACT only when the pCR rate was at least 44.6%. The development of effective NACT regimens is beneficial for breast cancer patients. Citation Format: Xiaoying Qiao, Taobo Hu, Baosheng Liang, Shu Wang. Rethinking the value of pathologic complete response rate for the survival outcomes of early triple-negative breast cancer treated with neoadjuvant chemotherapy: a systematic review and network meta-analysis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-03-05.

Abstract PO3-05-09: The impact of body mass index on CDK4/6 inhibitor treatment survival outcomes in metastatic breast cancer

Abstract Introduction: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) are important in the treatment of hormone receptor-positive (HR+)/HER2-negative metastatic breast cancer (MBC). Previous studies have shown that CDK4/6is affect metabolic processes and cell metabolism, including adipogenesis, lipid synthesis, and glucose regulation. Obesity has been associated with worse survival in breast cancer. We aimed to assess the effect of body mass index (BMI) on survival outcomes in patients treated with CDK4/6is for MBC. Methods: Patients diagnosed with metastatic HR+/HER2-negative BC and who were treated with palbociclib, ribociclib, or abemaciclib from 6/10/2015 to 12/28/2022 were selected from the Montefiore Health system database and followed until 3/24/2023. The patients were divided into three groups according to BMI level as follows; normal: 18.5-24.9 kg/m2, overweight: 25-29.9 kg/m2 and obese: ≥ 30 kg/m2. Patients were also stratified by BMI measured after 3 months of therapy. Characteristics of the patients and tumors in the subgroups were compared using chi-squared/Fisher’s exact test for categorical data and Kruskal-Wallis/Wilcox signed rank tests for continuous data. Kaplan-Meier and Cox proportional hazards analysis were used to compare overall survival (OS) and progression free survival (PFS). Results: Among 221 patients, 66 were normal weight, 78 were overweight, and 77 were obese. There was no statistically significant difference in clinicopathological characteristics among the cohorts. Neither BMI measured at baseline nor after 3 months of therapy had any association with OS (P = 0.8 at baseline and P = 0.1 after 3 months) or PFS (P = 0.4 at baseline and P = 0.6 after 3 months). Multivariable analysis showed no statistically significant association between BMI and worse OS (HR: 1.1 for overweight, P = 0.7; and 0.96 for obese, P = 0.9) or worse PFS (HR: 0.9 for overweight, P = 0.8; and 0.76 for obese, P = 0.5). Multivariate analysis revealed a significant effect of obese BMI after 3 months of treatment on OS (HR: 0.48, P = 0.035) but not on PFS (HR: 0.88, P = 0.8). Overweight BMI after 3 months of treatment was not found to have a significant effect on OS (HR: 0.49, P = 0.063) or PFS (HR: 0.89, P = 0.9). Conclusion: The clinical effectiveness of CDK4/6is was not found to be influenced by BMI measured prior to therapy; however, there may be an association between improved OS and obese BMI after 3 months of treatment. Median OS and PFS in patients with MBC comparing different BMI groups (normal, overweight, and obese) at baseline prior to therapy and after 3 months of therapy. Table 1 Baseline characteristics of patients with MBC comparing different BMI groups (normal, overweight, and obese) at baseline prior to therapy and after 3 months of therapy. Table 2 Table 3 Multivariable analysis of OS and PFS for patients with MBC comparing different BMI groups (normal, overweight, and obese) at baseline prior to therapy and after 3 months of therapy. Citation Format: Frank Zhang, Jesus Anampa Mesias. The impact of body mass index on CDK4/6 inhibitor treatment survival outcomes in metastatic 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 PO3-05-09.

Abstract PO1-16-11: Real-world features and outcomes of young advanced breast cancer (ABC) patients (pts) from RegistEM (GEICAM/2014-03) study

Abstract Background: BC is the most incident cancer worldwide in &amp;lt; 40 years old (y) women. Increasing body mass index and changes in reproductive history contribute to the growing incidence of premenopausal BC. A higher proportion of luminal B-like and estrogen receptor negative (ER─) tumors, an increased risk of early relapse, and more unfavorable longer-term outcomes for young women with ER+ tumors when compared to older women, have been reported. In this analysis, we focus on age-specific BC characterization from a real-world population-based perspective. Methods: Pts were enrolled in the non-interventional and ambispective RegistEM study in ABC diagnosed between 2016 and 2019. We describe the features and outcomes of &amp;lt; 50 y pts at their initial BC diagnosis according to their BC subtype. BC subtypes were based on the most recent tumor tissue sample (distant metastasis, and in its absence, primary BC). Comparisons between &amp;lt; 40 and ≥ 50 y groups were performed. Results: Pts &amp;lt; 50 y represent 39% (n=685) of total pts with available data (n=1739, any age group) in the registry. By age, 12% (n=212) were &amp;lt; 40y, and 27% (n=473) 40-49y. At first BC diagnosis, 75% and 25% pts had early BC (EBC) and de novo metastatic BC (MBC), respectively. In EBC pts, stage II (50%) and III (28%) were the most frequent at diagnosis; invasive non-special type carcinoma was the predominant morphology, and grade 2 was the most common histological grade, but grade 3 was predominant in TN pts and HER2+ &amp;lt; 40y pts. The median time to recurrence was &amp;lt; 2y in TN pts, 3y in HER2+ pts, and 6y in luminal HER2─ pts. At ABC diagnosis, the median age was 47y, all pts were female but one, 98% white, and 60% premenopausal (94% were premenopausal at EBC diagnosis). A family history of BC and/or ovarian cancer was reported in 34% pts, and a hereditary-risk genetic test was performed in 39% (254 of 652) pts; 12% (n=30) had BRCA1/2 mutations, with a proportion higher in TN pts (9 of 33, 27%) vs. luminal HER2─ (21 of 183, 12%) and HER2+ (0 of 38) pts. Visceral disease was the most frequent in all subgroups, highlighting statistical differences (p=0.022) between age groups ( &amp;lt; 40y 55% vs. ≥50y 71%) only in TN pts. 60% had ≤ 2 locations involved, similarly in all subgroups. The presence of &amp;gt;2 metastatic locations was statistically higher in HER2+ pts ≥50y (54%) vs both &amp;lt; 40y (32%) and 40-49y (48%). Brain disease was more present at ABC diagnosis in TN (9%) and HER2+ (7%) than in luminal HER2─ (3%). Median no. of treatment lines (L) was 3 (range 0-11), and median follow-up 44 mo (95% CI: 41-44). 99% pts received 1L, the distribution of treatments by BC subtype within each age subgroup was similar; median duration of 1L was 21 months (mo) in luminal HER2─, 17 mo in HER2+, and 5 mo in TN pts. 68% of pts who received 1L, reached 2L. Duration of 2L dropped dramatically: 8 mo in luminal HER2─, 6 mo in HER2+, and 2 mo in TN pts. No differences between ≥50y and the rest of pts were observed in PFS for any treatment line. 49% pts had died at the database cut-off date (05-April-23), with no differences between age groups, but TN pts had the highest death rate (80%). Additional data according to BC subtypes and age groups are in the table. Conclusions: Luminal HER2─ was the predominant BC subtype in all age subgroups. Visceral disease was more prevalent in young TN pts compared to older pts. TNBC pts experienced a shorter median time to recurrence and the highest mortality rate regardless of age, compared to HER2+ and luminal HER2- pts, indicating the need for targeted interventions in this subgroup. Citation Format: Sara López-Tarruella, Angel Guerrero, Isabel Álvarez, Silvia Antolin Novoa, Ariadna Tibau, Josefina Cruz, César A Rodríguez, Purificación Martínez, J. Ignacio Chacón, María Hernández, Mireia Margelí, Encarna Adrover, Catalina Falo, Iria González, Álvaro Rodríguez-Lescure, María Marín, César Gómez, Juan de la Haba-Rodríguez, J. José Illaramendi, Raquel Andrés, Andrea Blasco, Mª José Escudero, Susana Bezares, Federico Rojo. Real-world features and outcomes of young advanced breast cancer (ABC) patients (pts) from RegistEM (GEICAM/2014-03) 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 PO1-16-11.

Abstract PO1-09-11: Racial Differences in Pathologic Complete Response Rate and Overall Survival Following Neoadjuvant Chemotherapy for Breast Cancer

Abstract Background: Neoadjuvant chemotherapy (NAC) is increasingly used in the treatment of breast cancer and has been utilized in multiple clinical trials assessing the efficacy of novel therapies. Pathologic complete response (pCR) following NAC is associated with improved survival outcomes in breast cancer and pCR is a commonly used endpoint in clinical trials. Despite improvements in breast cancer survival using modern treatment regimens, Black women continue to experience worse survival outcomes as compared to White women. The objective of this study was to evaluate the association between race and clinical outcomes, specifically pCR rate, recurrence free survival and overall survival, in patients undergoing neoadjuvant chemotherapy at our institution. Methods: We conducted a retrospective review of patients who completed at least 75% of the recommended cycles of neoadjuvant chemotherapy for breast cancer between 2010 and 2016 and underwent surgery. Receptor subtypes were defined as HR+/HER2-negative, HER2+ or triple-negative. The association between race and pCR, defined as ypT0/ypTis ypN0, and survival endpoints of overall survival and recurrence free survival were analyzed using multivariable logistic regression and Cox proportional hazard models. Results: A total of 532 women met the inclusion criteria, 323 (60.7%) were White, 188 (35.3%) were Black and 21 (3.9%) were other/unknown. Median follow-up was 65 months. The receptor subgroups consisted of 195 (36.7%) HR+/HER2-negative cancers, 193 (36.3%) HER2+ cancers and 144 (27.1%) triple-negative cancers. No significant association between race and receptor subtype (p=0.55) or pre-treatment clinical stage (p=0.96) was observed. The overall observed pCR rate was 19% for Black patients and 27% for White patients, demonstrating a significantly different pCR rate by race in multivariate analysis (odds ratio of pCR White vs Black of 1.75; p=0.02). The largest discrepancy in pCR rate between White and Black patients was within subjects with triple-negative disease (pCR rate 44% White patients vs 27% Black patients, p=0.03). There was no association between recurrence free survival and race in univariate analysis (p=0.15). A significant difference in overall survival by race was observed using multivariable Cox proportions hazard model (hazard ratio Black vs White 1.77; p=0.03). Conclusions: In this retrospective analysis of patients receiving neoadjuvant chemotherapy, Black patients experienced a significantly lower pCR rate compared to White patients, with the biggest gap identified within triple-negative breast cancers. During the study period, Black patients also experienced a lower overall survival rate compared to White patients. Differences in the ability to achieve a pCR may be a contributing factor to the worse survival outcomes of Black patients. Citation Format: Chad Livasy, Erin Donahue, Brittany Neelands, Lejla Hadzikadic-Gusic, Terry Sarantou, Mckenzie Needham, Alicia Patrick, Arielle Heeke, Antoinette Tan, Richard White. Racial Differences in Pathologic Complete Response Rate and Overall Survival Following Neoadjuvant Chemotherapy for 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 PO1-09-11.

Abstract PO5-27-10: Next generation antibody drug conjugates: Multi-payload conjugates targeting multiple mechanisms of cell killing

Abstract Background: ADCs have had tremendous impact on patient outcomes in breast cancer and are rapidly moving towards second line use. However, many patients fail to respond or relapse after treatment with ADC therapies due to tumor heterogeneity and resistance to ADC payloads. Method: CatenaBio has developed a novel Multi-Payload-Conjugate (MPC) system capable of attaching distinct payloads at different sites to the same antibody, enabling the production of single-molecule targeted combination therapies with defined DAR. Results: We screened combinations of different payloads targeting several different mechanisms attached to trastuzumab at different drug-antibody ratios to optimize tumor cell killing. These targeted combination ADCs demonstrated robust killing in both HER2 high and low tumor cell lines. Conclusion: Antibody Drug Conjugates have revolutionized the treatment of high HER2 positive breast cancer. More recently advances have been made in the design of ADCs to expand indications to include HER2 low as well as HER2 negative patients. These constructs offer the next step in ADC design and allow for the combination of multiple mechanisms of action in a single MPC that are highly effective across multiple breast cancer cell lines. These molecules offer the potential to circumvent tumor resistance pathways and deliver deeper and more durable responses. Disclosures: Marco Lobba, Devin Trinter, Maxwell Nguyen, Daniel Gutierrez, Samantha Brady, Chanez Symister, Andrew Lau, Richard Kendall, and Saurabh Johri are employed by Catena Biosciences. Matthew Francis is a co-founder and advisor to Catena Biosciences. Citation Format: Marco Lobba, Devin Trinter, Maxwell Nguyen, Daniel Gutierrez, Samantha Brady, Chanez Symister, Andrew Lau, Richard Kendall, Saurabh Johri, Matthew Francis. Next generation antibody drug conjugates: Multi-payload conjugates targeting multiple mechanisms of cell killing [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 PO5-27-10.