Predictive value of MGMT, hMLH1, hMSH2 and BRCA1 protein expression for pathological complete response to neoadjuvant chemotherapy in basal-like breast cancer patients

Abstract

To evaluate the importance of biological markers to predict pathologic complete response (pCR) to neoadjuvant chemotherapy (NACT) in patients with locally advanced basal-like breast cancers (BLBCs). Thirty-two BLBC patients receiving NACT with an anthracycline-based regimen plus taxane were included in this study. The immunoreactivities of MGMT, MLH1, MSH2 and BRCA1 before and after NACT were evaluated. A pCR was obtained in 10 of 32 cases (31%). Cancer-related (P = 0.013) and disease-free (P = 0.023) survival rates were significantly higher in the pCR group than in the non-pCR group. In biopsy samples before NACT, attenuated expression of MGMT, MLH1, MSH2 and BRCA1 was observed in 12/32 (38%), 0/32 (0%), 5/32 (16%) and 28/32 (88%) cases, respectively. On evaluation of pCR, patients' characteristics (patients' age, menopausal status, or clinical and pathological stages) and immunohistochemical patterns, attenuated expression of MGMT was only found to be significantly predictive of a pCR (P = 0.018). Paired biopsy sample before NACT and a surgical tumor material after NACT were available for 19 cases of non-pCR. In these cases, decrease in expression during NACT were more frequently observed for MGMT as compared to MLH1, MSH2 or BRCA1 (P = 0.021). MGMT status is a predictive factor for pCR with neoadjuvant anthracycline-based plus taxane combination chemotherapy, which may be helpful in the selection of appropriate NACT for Japanese patients with BLBC.