Neoadjuvant drug therapy and oncological outcomes in patients with stage I–II breast cancer

Objective. To determine clinical and morphological predictors influencing the achievement of pCR in patients with breast cancer (BC) after neoadjuvant therapy (NAT), and to evaluate oncological outcomes in the group with and without NAT. Material and methods. A single-center retrospective non-randomized study was conducted, for which 984 patients with stage I–II breast cancer treated at the P.A. Herzen Moscow Oncology Research Institute from 2014 to 2022 were examined, in whom the surgical stage included subcutaneous/skin-sparing mastectomies with simultaneous reconstruction. The study participants were divided into 2 groups: Group 1 (n=276) — patients who received NAT courses at stage 1, Group 2 (n=708) — individuals who underwent surgical treatment at stage 1. Depending on the biological type, NAT included the following treatment regimens and number of courses: 4AC+4T for the luminal HER2-negative type, 6TCN or 6TCN+pertuzumab for the HER2-positive type, 4AC+4 paclitaxel/carboplatin for the triple-negative type. Subcutaneous mastectomy with reconstruction was performed in 617 (60.5%) patients, skin-sparing mastectomy — in 403 (39.5%) patients. Results. When analyzing the treatment results of 276 patients in group 1, a complete pathomorphological response (pCR) according to the morphological examination of the surgical material was achieved in 141 (49%) cases. The relative risk (RR) of developing local recurrence of breast cancer was 0.528 (CI 0.237—1.177) in group 1 and 1.962 (CI 0.880—4.375) in group 2. Metastases in the 1st group were detected in 5.4% of patients (pCR — 2.1%, non pCR — 8.8%), 5-year overall survival was 98.6%, event-free survival reached 92.1%, in the 2nd group metastases were detected in 5.4% of patients, overall survival for 5 years was 98.2%, and event-free survival was recorded at 89.8%. Conclusion. Achieving a complete pathological response is a marker of a decrease in the frequency of metastases and relapse. Achieving pCR reduces the risk of an adverse event, which follows from the analysis of event-free survival, which was 94.3% versus 87.8% among patients with pCR and non pCR, respectively.