Neoadjuvant Pembrolizumab Plus Chemotherapy in Early-Stage Triple-Negative Breast Cancer: A Nationwide Retrospective Turkish Oncology Group Study

Simple Summary This study investigates the real-world efficacy and safety of combining pembrolizumab, a novel immunotherapy agent, with chemotherapy in early-stage triple-negative breast cancer treatment. We specifically aimed to validate clinical trial results in routine practice. A total of 108 Turkish patients receiving neoadjuvant therapy were examined. The combined regimen demonstrated high efficacy, with 64% of patients achieving pathological complete response, and exhibited generally favorable safety profiles with predominantly mild adverse events. These findings support the use of this combination as a standard treatment for this aggressive breast cancer subtype. However, the results underscore the need for further research to identify optimal patient selection criteria, which can inform oncologists' decision-making and potentially enhance outcomes for patients with triple-negative breast cancer.Abstract Background/Objectives: Following the results of the phase 3 KEYNOTE-522 trial, the U.S. Food and Drug Administration approved pembrolizumab, a humanized IgG4 kappa monoclonal antibody, in combination with neoadjuvant chemotherapy as a new standard of care for high-risk early-stage triple-negative breast cancer (TNBC). This retrospective, multicenter study in T & uuml;rkiye assessed the real-world efficacy and safety of neoadjuvant pembrolizumab combined with chemotherapy in early-stage TNBC. Methods: The study included 108 patients treated between 2021 and 2023 across 14 oncology centers. Three distinct neoadjuvant regimens incorporating pembrolizumab were administered at the discretion of the treating physicians. The primary outcomes were the pathological complete response (pCR) rate after neoadjuvant therapy and the 2-year event-free survival (EFS) and overall survival (OS) rates. Results: The observed pCR rate was 63.9%, closely mirroring the 64.8% reported in the KEYNOTE-522 trial. At the two-year mark, the EFS rate was 87.2% and the OS rate was 92.3%. Multivariable analysis identified pCR as the sole independent predictor of both EFS and OS. The safety profile was consistent with previous clinical trial data, with most adverse events being of grade 1-2 in severity. Conclusions: These findings provide valuable real-world confirmation of the efficacy and safety of neoadjuvant pembrolizumab-chemotherapy in early-stage TNBC, complementing evidence from randomized trials.