To explore the relationship of the expression of CK5/6 with clinicopathological features, prognosis, and efficacy of neoadjuvant chemotherapy (NAC) in triple-negative breast cancer (TNBC).

A retrospective analysis for CK5/6 expression, clinicopathological features, prognosis, and efficacy of NAC was performed on 452 patients treated at Peking University First Hospital from 2009 to 2020 with non-metastatic breast cancer who were confirmed to be triple-negative by pathological examination and had relatively complete clinicopathological data.

The age of the patients ranged from 21 to 88 years (mean age, 52.9 years). The positive rate of CK5/6 in the overall group of patients was 65.3%, and early stage, higher histological grade, and Ki67 expression were factors related to higher CK5/6 expression. There was no significant correlation between CK5/6 expression and pathological complete response rate (pCR), event-free survival (EFS), and breast cancer-specific survival (BCSS). The pCR rate in CK5/6-positive patients was 27.5%. The 3-year and 5-year EFS rates were 86.1% and 84.1%, respectively; the 3-year and 5-year BCSS rates were 94.3% and 91.1%, respectively. EFS and BCSS were higher in CK5/6-positive patients treated with platinum-based neoadjuvant chemotherapy.

CK5/6 is an important biomarker of TNBC, whose expression is correlated with histological grade and tumor proliferation ability, but it has no significant correlation with prognosis. CK5/6 positivity may be associated with the benefit of platinum-based chemotherapy.