BRCA-1 methylation and TP53 mutation in triple-negative breast cancer patients without pathological complete response to taxane-based neoadjuvant chemotherapy

Abstract

Introduction: Triple-negative breast cancer (TNBC) patients without pathological complete response (pCR) to neoadjuvant chemotherapy have an unfavourable prognosis. TNBC harbouring BRCA-1 germline mutations may be less responsive to taxanes, while sensitivity to DNA-damaging agents is retained. A similar effect was seen in tumours with epigenetic BRCA-1 silencing. Patients without pCR to neoadjuvant chemotherapy consisting of epirubicin plus docetaxel routinely received post-operative CMF at our centre. Here, we investigated the effect of adjuvant CMF in patients with or without BRCA-1 methylation or TP53 mutation.

Methods: DNA was extracted from formalin-fixed paraffin-embedded tissue. For determining BRCA-1 methylation status, quantitative methylation-specific PCR was performed. For the investigation of TP53 mutation status, DNA was PCR amplified and sequenced by Sanger sequencing.

Results: Twenty-four patients were included; BRCA-1 methylation was present in 41.7 %, while TP53 mutations were observed in 66.7 %. At a median follow-up of 27.5 months, 20 % of patients with BRCA-1 methylation had a disease-free survival (DFS) event, as compared to 64.3 % in the non-methylated group (p = 0.0472). Median DFS in the non-methylated group was 16 months and was not reached in the methylated group (n.s.). No association TP53 mutation status with clinical outcome was observed.

Conclusions: Adjuvant CMF is of limited activity in TNBC refractory to taxane-based neoadjuvant chemotherapy. In this population, BRCA-1 methylation was associated with a significant decrease in DFS events suggesting a better prognosis and potentially retained activity of DNA-damaging agents.