Abstract PS13-08: Predictors and long-term outcome of pathologic complete response in patients receiving neoadjuvant chemotherapy for breast cancer - an NCDB analysis

Abstract

Abstract Background: Among women with high-risk early stage breast cancer, neoadjuvant chemotherapy (NCT) is increasingly utilized. The Collaborative Trials in Neoadjuvant Breast Cancer working group studied 13,000 patients from 12 large trials involving NCT and concluded that pathologic complete response (pCR) resulted in significantly better outcomes with respect to both disease recurrence and mortality. This National Cancer Database (NCDB) study aims to gather patient and tumor characteristics to further identify prognosticators of pCR, and determine which subgroups achieving pCR have the greatest survival benefit. Methods: Retrospective analysis using NCDB data from 2004-2015 identified 46,836 women ≥18 years with stage I to III breast cancer who received NCT. Achievement of pCR was defined as ypT0 ypN0 or ypT0/is ypN0. Tumor and patient characteristics were evaluated, and multivariate logistic regression was used to calculate odds ratio (OR) of pCR. Kaplan-Meier curves were constructed for calculation of overall survival (OS) at 5 years. Hazard ratios (HR) were estimated from Cox models. Propensity score weighting was used to adjust for confounding effects of various factors on survival via Cox regression. Results: Patients were more likely to achieve pCR with ductal vs. lobular histology (OR 1.62 [95% CI 1.414-1.872]), grade 3 vs. 1 (OR 1.606 [95% CI 1.394-1.849]), stage 3 vs. 1 (OR 1.76 [95% CI 1.623-1.908]), ER+PR- vs. ER+PR+ (OR 2.004 [95% CI 1.855-2.165]), ER-PR- vs. ER+PR+ (OR 2.572 [95% CI 2.425-2.729]), age <60 (OR 1.43 [95% CI 1.32-1.55]), Charlson-Deyo combined comorbidity (CDCC) score of 0 vs. 2 (OR 1.27 [95% CI 1.04-1.54]), and private insurance vs. uninsured (OR 1.24 [95% CI 1.09-1.41]). HR for death adjusted by propensity score in patients attaining pCR vs. non-pCR was 0.346 (95% CI 0.325-0.368) for the overall cohort, 0.591 (95% CI 0.513-0.681) for ER+PR+ patients, 0.373 (95% CI 0.315-0.442) in the ER+PR- group, and 0.307 (95% CI 0.284-0.332) for ER-PR- patients. Achieving pCR conferred better OS in all subgroups with higher magnitude in hormone negative patients (table 1). Conclusions: This study not only highlights factors associated with achieving pCR after neoadjuvant chemotherapy for breast cancer, but also demonstrates that attaining pCR reduces the risk of death by 65.4% in all patients regardless of receptor subtype. Furthermore, the survival curve increasingly separates with time. Our study reveals an intriguing observation that ER+PR+ patients who attain pCR have 40.9% decreased mortality compared to non-pCR. Limitations of this analysis include the lack of HER2 status and that conclusions are made from non-population based observational data. Despite utilization of propensity score weighting, there may have been confounders that were not adjusted for by the multivariate model. Future analysis is needed to identify HER2 status, as HER2-positive patients may have contributed to the OS benefit in the subgroups. Nonetheless, these data are among the first to suggest that hormone-positive patients derive long-term survival benefit from achievement of pCR, albeit to a lesser extent than hormone-negative subtypes. Table 1. 5-year survival estimates from Kaplan-Meier analysispCRNon-pCRSurvival differencep (95% CI)All patients0.88500.73840.14657<0.0001 (0.1364-0.1567)ER+PR+0.90300.81170.09121<0.0001 (0.0744-0.1079)ER+PR-0.89620.70740.18879<0.0001 (0.1609-0.2166)ER-PR+0.88070.63880.24198<0.0001 (0.1719-0.3120)ER-PR-0.87570.64660.22913<0.0001 (0.2131-0.2451) Citation Format: Lauren Mikesell Panebianco, Prashanth Ashok Kumar, Shreya Sinha, Dongliang Wang, Danning Huang, Abirami Sivapiragasam. Predictors and long-term outcome of pathologic complete response in patients receiving neoadjuvant chemotherapy for breast cancer - an NCDB analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS13-08.