Prognostic value of HER2 2 + expression in patients with TNBC receiving adjuvant capecitabine.

Background: In triple-negative breast cancer (TNBC) patients receiving adjuvant capecitabine, the impact of HER2 expression on survival outcomes is unclear.

Methods:  Between June 2017 and December 2023, 112 patients with TNBC who received adjuvant capecitabine due to residual masses after neoadjuvant chemotherapy (NACT) in three hospitals were identified. HER2 is analyzed through immunohistochemistry (IHC) and/or in situ hybridization in the core biopsy and/or post-surgical histopathologies. Relapse-free survival (RFS) and overall survival (OS), according to HER2 expression (0, 1 + , 2 +) status, were calculated (Kaplan-Meier method).

Results:  Seventy-eight (69.6%) patients had HER2 zero, 20 (17.9%) patients had HER2 + 1, and 14 (12.5%) patients had HER2 + 2/ISH- BC. The 5-year OS was 62.6%, and the 5-year RFS was 55.8%. HER2 2 + expression was associated with worse OS (27.5 vs. 84.5 months; HR 4.82, 95% CI 2.15-10.80, p < 0.001) and worse RFS (11.90 months vs. not reached; HR 4.30, 95% CI 2.06-8.99, p < 0.001) compared with HER2 0/1 + expression. The 5-year OS rates were 32.7% and 72.1%, and the 5-year RFS rates were 30.6% and 64.7% in the HER2 2 + and HER2 0/1 + groups, respectively. No statistically significant differences were detected in clinicopathologic features or pathologic responses to NACT according to the HER2 expression level.

Conclusions:  Despite the use of the adjuvant capecitabine in HER2 2 + TNBC patients, these poor results will pave the way for further investigations of anti-HER2 therapeutic agents in adjuvant treatment.