Pathologic complete response after neoadjuvant chemotherapy in HER2-overexpressing breast cancer according to hormonal receptor status

Objective: For patients with HER2-positive breast cancer, the prognostic impact of pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) is unclear when stratified by hormonal receptor (HR) status; however, the impact of pCR on survival when stratified by hormonal receptor (HR) status is uncertain. Patients and methods: This multicenter retrospective study investigated the predictors of pCR and its prognostic value in Japanese patients 366 HER2-positive breast cancer who received NAC. pCR was defined as no invasive residual tumor in the breast or axilla. Results: Median follow-up was 55 months. Multivariate analysis revealed that HR status (OR, 0.37; p<0.001) was one of the independent predictors of pCR. Five-year recurrence-free survival was higher in HR-negative patients with pCR (93%) than in those without pCR (68%), and pCR was independently prognostic (hazard ratio, 0.32; p=0.005). However, 5-year recurrence-free survival was not different between HR-positive patients with pCR (94%) and those without pCR (84%), and pCR was not significantly prognostic (hazard ratio, 0.53; p=0.39). In addition, 5-year overall survivals were high and similar (97% in pCR, 94% in non-pCR). Among 204 patients treated with neoadjuvant trastuzumab, pCR was not significantly prognostic in the HR-positive group (hazard ratio, 0.63; p=0.56). Conclusion: Our study suggested that the HER2-positive HR-positive patients had a good prognosis despite the lower achievement rate of pCR, whose prognostic impact was smaller than that in the HER2-positive HR-negative patients. The treatment strategy for HER2-positive breast cancer can be stratified by HR status.