Haplotype-Based Analysis of Genes Associated With Risk of Adverse Skin Reactions After Radiotherapy in Breast Cancer Patients

Purpose: To identify haplotypes of single nucleotide polymorphism markers associated with the risk of early adverse skin reactions (EASRs) after radiotherapy in breast cancer patients. Methods and Materials: DNA was sampled from 399 Japanese breast cancer patients who qualified for breast-conserving radiotherapy. Using the National Cancer Institute-Common Toxicity Criteria scoring system, version 2, the patients were grouped according to EASRs, defined as those occurring within 3 months of starting radiotherapy (Grade 1 or less, n = 290; Grade 2 or greater, n = 109). A total of 999 single nucleotide polymorphisms from 137 candidate genes for radiation susceptibility were genotyped, and the haplotype associations between groups were assessed. Results: The global haplotype association analysis (p < 0.05 and false discovery rate < 0.05) indicated that estimated haplotypes in six loci were associated with EASR risk. A comparison of the risk haplotype with the most frequent haplotype in each locus showed haplotype GGTT in CD44 (odds ratio [OR] = 2.17; 95% confidence interval [CI], 1.07-4.43) resulted in a significantly greater EASR risk. Five haplotypes, CG in MAD2L2 (OR = 0.55; 95% CI, 0.35-0.87), GTTG in PTTG1 (OR = 0.48; 95% CI, 0.24-0.96), TCC (OR = 0.48; 95% CI, 0.26-0.89) and CCG (OR = 0.50; 95% CI, 0.27-0.92) in RAD9A, and GCT in LIG3 (OR = 0.46; 95% CI, 0.22-0.93) were associated with a reduced EASR risk. No significant risk haplotype was observed in REV3L. Conclusion: Individual radiosensitivity can be partly determined by these haplotypes in multiple loci. Our findings may lead to a better understanding of the mechanisms underlying the genetic variation in radiation sensitivity and resistance among breast cancer patients