Association of XRCC1 and XRCC3 gene haplotypes with the development of radiation‑induced fibrosis in patients with nasopharyngeal carcinoma

Radiation‑induced fibrosis is one of the late complications of radiotherapy (RT) for nasopharyngeal carcinoma (NPC). The aim of this study was to investigate the association between X-ray repair cross-complementing protein 1 and 3 (XRCC1 and XRCC3, respectively) gene haplotypes and radiation‑induced fibrosis in NPC patients. Genomic DNA was extracted from blood samples of 120 NPC patients previously treated with RT. In total, 12 tag single‑nucleotide polymorphisms (SNPs) were selected from the XRCC1 and XRCC3 genes and were genotyped using restriction fragment length polymorphism analysis or unlabeled probe melting analysis. Single‑marker and haplotype analyses were performed using multivariate logistic regression analysis. The functional variant rs861539 of XRCC3 may be associated with radiation‑induced fibrosis [asymptotic P‑value (Pasym)<0.05]. No significant association was observed between radiation‑induced fibrosis and any of the tag SNPs of XRCC1 and XRCC3 in either single‑marker or haplotype analysis after 10,000 permutations [empirical P‑value (Pemp)>0.05]. Our preliminary results indicated that the rs861539 variant of XRCC3 may be associated with an increased risk of radiation‑induced fibrosis; however, a large‑scale study is required to confirm this result.