Impact of BRCA1/2 germline mutation on the incidence of second primary cancer following postoperative radiotherapy in patients with triple-negative breast cancer

Background and purpose: BRCA1/2 plays an important role in maintaining the genome stability. Whether BRCA1/2 germline mutation could increase the tumor sensitivity to radiotherapy, thereby inducing secondary primary cancer after radiotherapy is unclear. This study aimed to investigate whether postoperative radiotherapy is a risk factor for the development of second primary cancer in triple-negative breast cancer (TNBC) patients with BRCA1/2 germline mutation. Methods: This research was based on a previously reported retrospective cohort, i.e., the Fudan University Shanghai Cancer Center TNBC cohort. Between January 1, 2007 and December 31, 2014, a total of 292 female TNBC patients with BRCA1/2 mutation were enrolled. We performed logistic regression analysis in patients without BRCA1/2 germline mutation (n=261) and BRCA1/2 germline mutation patients (n=31), respectively, to assess the risk factors affecting the incidence of second primary cancer. We then performed interactive analysis on the above two analyses to evaluate the interactive effect between BRCA1/2 germline mutation and postoperative radiotherapy. P