Influence of histopathological changes after neoadjuvant chemotherapy on the survival of breast cancer patients.

Background: Neoadjuvant chemotherapy (NACT) is an established form of therapy for early breast cancer (BC). The aim of our study was to analyze histopathological parameters before and after receiving NACT and to determine the influence of these changes on prognosis of BC patients.

Methods: We retrospectively analyzed data of patients with primary early BC, diagnosed between January 2012 and December 2019, and NACT, followed by primary surgery. Patients achieving pathological complete response (pCR) were excluded. For the outcome analysis, disease-free survival (DFS) and overall survival (OS) were defined.

Results: A total of 237 tumors were analyzed in the study. The conversion rates of tumor grade, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), Ki67 status, and BC subtype were 34.6 %, 3.4 %, 14.3 %, 4.6 %, 30.0 %, and 28.7 %, respectively. After a median follow-up of 58.03 months, we found an association between consistently negative ER/PR with the worst prognosis (DFS and OS) (ER p < 0.0001 for both; PR p = 0.0003, p = 0.0004, respectively). The conversion from Ki67 ≥14 % to <14 % led to an improved outcome compared to a constant Ki67 ≥14 % (DFS p = 0.003, OS p = 0.001). Tumor residuals with a non-triple-negative (nTN) subtype (TN → nTN) showed a better prognosis than those with TN subtype (nTN → TN) (DFS and OS p < 0.0001).

Conclusions: After NACT, tumor grade and Ki67 showed the highest conversion rates between primary biopsy and tumor residual. Depending on changes in ER, PR, Ki67, and subtype, we found significant differences in the prognosis of the patients.