Complete pathological response following neoadjuvant FOLFOX chemotherapy in BRCA2-mutant locally advanced rectal cancer: a case report

BACKGROUND: Patients with locally advanced rectal cancer (LARC) achieving a pathological complete response (pCR) to neoadjuvant treatment usually have a good prognosis, but only accounted for less than 20%. CASE PRESENTATION: We report a case of a 25-year-old male with LARC treated with neoadjuvant FOLFOX chemotherapy, and experienced a pCR. The next-generation sequencing analysis revealed the presence of breast cancer gene 2 (BRCA2) somatic mutation and an increased somatic mutational load without microsatellite instability (MSI). To our knowledge, this is the first report of BRCA2 mutant LARC that demonstrated significant benefit from FOLFOX neoadjuvant treatment. CONCLUSIONS: This case indicated an association of BRCA2 mutation with high mutation loads and an excellent response of oxaliplatin-based chemotherapy regimen for LARC. Our findings encourage further studies to analyze BRCA mutations in patients with LARC, especially for those patients unable or unwilling to receive radiotherapy.