[Application value of DNA damage repair variants in adjuvant therapy of triple negative breast cancer].

Abstract

Objective: To investigate the correlation between adjuvant chemotherapy with platinum-containing regimens and DNA damage repair (DDR) defects in early-stage triple negative breast cancer (TNBC), and to provide a basis for precise treatment of TNBC. Methods: Next-generation sequencing (NGS) testing was performed on postoperative breast cancer specimens selected from the Cancer Hospital of Chinese Academy of Medical Sciences from June 2009 to October 2015 to analyze the correlation between DDR gene variants and the efficacy of adjuvant chemotherapy with TNBC platinum-containing regimens, and thus to screen the superior population for adjuvant chemotherapy with TNBC platinum-containing regimens. The study used t-test, χ(2) test, Fisher's exact test, rank sum test and multifactorial logistic analysis to assess the associations between mutated genes and clinicopathological characteristics and prognosis, and Log-rank test and Cox proportional risk model were used for survival and correlation analysis. Results: NGS results were successfully obtained in 149 patients (74 in the platinum-containing group and 75 in the platinum-free group), with a 97.3% (145/149) DDR gene mutation rate and a median number of 4 mutations in all patients. 5-year disease-free survival (DFS) was 85.4% and 75.0% for patients with DDR gene mutations and DDR gene wild-type, respectively, without statistical difference (P=0.825). The 5-year DFS rates of patients with homologous recombination repair (HRR) pathway mutation were 84.6% in platinum-containing (TCb) group and 84.9% in platinum-free (EC-T) group (P=0.554), respectively. The 5-year DFS rates of patients with and without mutations in the platinite-containing HRR pathway were 84.9% and 85.0%, respectively (P=0.751). The number of DDR pathways with mutations and the number of DDR gene mutations were not associated with prognosis (both P>0.05). PIK3CA mutation patients in TCb group had a worse prognosis than wild-type patients (5-year DFS were 71.4% and 88.1%, P=0.037), and KMT2D mutation patients in EC-T group had a worse prognosis than wild-type patients (5-year DFS were 76.9% and 86.8%, P=0.039). Conclusions: DDR gene variation is common in TNBC, more clinical studies are needed to prove whether DDR variation can serve as effective biomarkers for treatment with platinum.