Meta-analysis on association of pathological complete response with long-term survival outcomes in triple-negative breast cancer

Background Neoadjuvant studies in breast cancer (BC) patients have well-demonstrated that attaining pathological complete response (pCR) is associated with improved event-free survival (EFS) and overall survival (OS); and the association is strong in triple negative BC (TNBC) subtype. This study aimed to comprehensively evaluate the association of pCR and survival outcomes in TNBC by incorporating most recent studies; and to explore the impact of different study settings, thresholds of hormone receptor positivity defining TNBC and adjuvant chemotherapy usage on this association. Methods A literature search of neoadjuvant studies in TNBC was conducted up to October 2018. Clinical trials (CTs), real-world evidence (RWE) studies and meta-analyses (MA) with EFS/OS reported by pCR outcome were included. Main analyses were restricted to pCR definition of absence of tumor in the breast and axillary nodes, which is aligned with FDA guidance. Hazard ratios (HRs) evaluating the association between pCR and EFS/OS were derived from meta-analyses using fixed-effect and random-effects models. To further quantify the association, meta-analyses were conducted to synthesize the published survival curves by pCR outcome. A random-effects frailty model was utilized to account for between-study variation. Results Four randomized CTs, 2 single-arm CTs, 18 RWE studies and 1 MA for a total of 4,330 patients with TNBC were included in this study. Achieving pCR was strongly associated with improved survival outcomes (HR of EFS: 0.26, 95% CI: 0.22-0.30; and HR of OS: 0.20, 95% CI: 0.16-0.25). HR results were similar across study settings of CTs, RWE and MA. TNBC definition and adjuvant chemotherapy use did not have significant impact on HR results. The meta-analyses showed numerically longer survival in studies that reported adjuvant chemotherapy usage compared with those which did not, irrespective of attainment of pCR. Conclusions This study confirms the strong association between pCR and survival outcomes in TNBC based on evidence synthesis from both clinical and real-world settings. In addition, this study suggests potential survival benefit of subsequent adjuvant therapy for TNBC patients who received neoadjuvant therapy. Legal entity responsible for the study Merck & Co., Inc. Funding Merck & Co., Inc. Disclosure P.A. Fasching: Advisory / Consultancy: Merck & Co., Inc. M. Huang: Full / Part-time employment: Merck & Co., Inc. J. Cortes: Advisory / Consultancy: Merck & Co., Inc. J. Zhao: Full / Part-time employment: Merck & Co., Inc. J. O’Shaughnessy: Advisory / Consultancy: Merck & Co., Inc. P. Hu: Full / Part-time employment: Merck & Co., Inc. A. Haiderali: Full / Part-time employment: Merck & CO., Inc. V. Karantza: Full / Part-time employment: Merck & Co., Inc. G. Aktan: Full / Part-time employment: Merck & Co., Inc. A. Briggs: Advisory / Consultancy: Merck & Co., Inc. S. Ramsey: Advisory / Consultancy: Merck & Co., Inc. C.Z. Qi: Advisory / Consultancy, Employee of Analysis Group, Inc., which has received consulting fees from Merck & Co., Inc.: Merck & Co., Inc. J. Xie: Advisory / Consultancy, Employee of Analysis Group, Inc., which has received consulting fees from Merck & Co., Inc.: Merck & Co., Inc. C. Gu: Advisory / Consultancy, Employee of Analysis Group, Inc., which has received consulting fees from Merck & Co., Inc.: Merck & Co., Inc. K. Qian: Advisory / Consultancy, Employee of Analysis Group, Inc., which has received consulting fees from Merck & Co., Inc.: Merck & Co., Inc. M. Yuan: Advisory / Consultancy, Employee of Analysis Group, Inc., which has received consulting fees from Merck & Co., Inc.: Merck & Co., Inc. E.Q. Wu: Advisory / Consultancy, Employee of Analysis Group, Inc., which has received consulting fees from Merck & Co., Inc.: Merck & Co., Inc.