Mitomycin C in the treatment of early triple-negative locally advanced BRCA-associated breast cancer

Rationale. BRCA1 associated triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer. At the same time, carcinomas that develop in carriers of BRCA1 mutations are characterized by extremely high sensitivity to DNA-damaging chemotherapy. Mitomycin C alone or in combination with platinum agents has already demonstrated promising results in the treatment of BRCA-associated ovarian cancer (OC) and metastatic breast cancer. In this article, we present the results of a retrospective study aimed at comparing standard neoadjuvant chemotherapy regimens (NACT) with mitomycin-based regimens for primary locally advanced BRCA1-associated TNBC.The aim of the study is to determine the effectiveness of the combination of mitomycin and platinum compounds during neoadjuvant therapy in patients with primary locally advanced BRCA1 – associated TNBC.Materials and methods. The study included 89 patients diagnosed with primary locally advanced BRCA1-associated TNBC. Patients were divided into three groups depending on the therapy: 1) 4 cycles of anthracycline and cyclophosphamide followed by 12 weekly injections of paclitaxel (n = 48) (AC + T), 2) 4 cycles of anthracycline and cyclophosphamide followed by 12 weekly injections of paclitaxel and carboplatin (n = 27) (AC + TCbP), 3) mitomycin C plus platinum followed by 12 weekly injections of paclitaxel (n = 14) (MR + T). Pathological complete response (pCR) rates were compared.Results. The pCR rate in the MP+T group was 10/14 (71%). In patients with BRCA1-associated breast cancer who received AC + T and AC + TCbP regimens as NACT, the pCR rate was 17/48 (35%) and 19/27 (70%), respectively. The difference in pCR rate between mitomycin-containing therapy and the standard AC + T regimen was statistically significant (p = 0.03); the frequency of regressions was comparable to the frequency in the AC + TCbP group. During the 20-month follow-up period, no relapses were observed in the MR + T group. Relapses were more frequent in the AC + T group compared with the AC + TCbP group (16/48 (33%) vs 1/27 (4%), p = 0.003, Fisher’s exact test). The toxicity profile of the mitomycin-containing regimen included hematologic adverse events, the most common of which were anemia and leukopenia. Compared to standard regimens, nausea was significantly less pronounced. No patients reported alopecia with this regimen.Conclusions. The addition of mitomycin C to neoadjuvant therapy for BRCA1-associated TNBC may be a promising treatment option for this category of patients and merits further study.