Tumor histological subtyping determined by hormone receptors and HER2 status defines different pathological complete response and outcome to dose-dense neoadjuvant chemotherapy in breast cancer patients.

PURPOSE: To assess the impact in pathological complete response (pCR) and outcome of two dose-dense neoadjuvant chemotherapy (DDNC) regimens among different histological subtypes determined by hormonal receptor (HR) and HER2 status in breast cancer patients.

METHODS: A total of 127 breast cancer patients were treated with DDNC in two prospective studies. A: adriamycin 40 mg/m(2) on day (d) 1 plus paclitaxel 150 mg/m(2) and gemcitabine 2,000 mg/m(2) on d2 for six cycles (n = 54). B: epirubicin 90 mg/m(2), cyclophosphamide 600 mg/m(2) on d1 for three cycles, followed by paclitaxel 150 mg/m(2) and gemcitabine 2,500 mg/m(2) on d1 ± trastuzumab according to HER2 status (n = 73). Histological subtypes of breast cancer were 49 % HR+/HER2-, 17.5 % HR+/HER2+, 13.5 % HR-/HER2+ and 20 % HR-/HER2-.

RESULTS: pCR (absence of invasive cells in breast and lymph node) was achieved in 35 patients (28 %). The pCR rate was significantly different between histological subtypes: HR+/HER2- (9 %), HR+/HER2+ (23 %), HR-/HER2+ (50 %), HR-/HER2- (56 %) (p < 0.001). The median follow-up was 81 months (r: 15-150 months). HR-/HER2- tumor subtype had a significantly worse DFS compared to HR+/HER2- (p = 0.02), RH+/HER2+ (p = 0.04) and HR-/HER2+ tumor subtypes (p = 0.02). HR-/HER2- tumor subtype had a significantly shorter OS compared to HR+/HER2- (p = 0.007), RH+/HER2+ (p = 0.05), and HR-/HER2+ (p = 0.03) tumor subtypes. However, no significant difference was observed in DFS and OS among HR-/HER2- tumors that achieved a pCR.

CONCLUSIONS: HR-/HER2- and HR-/HER2+ subtypes had a high pCR rate to DDNC. HR-/HER2- tumors had a worse outcome compared to other tumor subtypes but no significant difference was observed among HR-/HER2- tumors that achieved a pCR.