ATM polymorphisms are associated with risk of radiation-induced pneumonitis.

PURPOSE Since the ataxia telangiectasia mutated (ATM) protein plays crucial roles in repair of double-stranded DNA breaks, control of cell cycle checkpoints, and radiosensitivity, we hypothesized that variations in this gene might be associated with radiation-induced pneumonitis (RP). METHODS AND MATERIALS A total of 253 lung cancer patients receiving thoracic irradiation between 2004 and 2006 were included in this study. Common Terminology Criteria for Adverse Events version 3.0 was used to grade RP. Five haplotype-tagging single nucleotide polymorphisms (SNPs) in the ATM gene were genotyped using DNA from blood lymphocytes. Hazard ratios (HRs) and 95% confidence intervals (CIs) of RP for genotypes were computed by the Cox model, adjusted for clinical factors. The function of the ATM SNP associated with RP was examined by biochemical assays. RESULTS During the median 22-month follow-up, 44 (17.4%) patients developed grade > or = 2 RP. In multivariate Cox regression models adjusted for other clinical predictors, we found two ATM variants were independently associated with increased RP risk. They were an 111G > A) polymorphism (HR, 2.49; 95% CI, 1.07-5.80) and an ATM 126713G > A polymorphism (HR, 2.47; 95% CI, 1.16-5.28). Furthermore, genotype-dependent differences in ATM expression were demonstrated both in cell lines (p < 0.001) and in individual lung tissue samples (p = 0.003), which supported the results of the association study. CONCLUSIONS Genetic polymorphisms of ATM are significantly associated with RP risk. These variants might exert their effect through regulation of ATM expression and serve as independent biomarkers for prediction of RP in patients treated with thoracic radiotherapy.