, and Polymorphisms as Potential Predictive Biomarkers of Adjuvant Radiotherapy Toxicity in Early HER2-Positive Breast Cancer.

Radiotherapy (RT) for breast cancer significantly impacts patient survival and causes adverse events. Double-strand breaks are the most harmful type of DNA damage associated with RT, which is repaired through homologous recombination (HRR). As genetic variability of DNA repair genes could affect response to RT, we aimed to evaluate the association of polymorphisms in HRR genes with tumor characteristics and the occurrence of RT adverse events in early HER2-positive breast cancer. Our study included 101 breast cancer patients treated with adjuvant RT and trastuzumab. All patients were genotyped for eight single nucleotide polymorphisms in , and using competitive allele-specific PCR. Carriers of rs1799794 GG genotype were less likely to have higher tumor differentiation grade (OR = 0.05, 95% CI = 0.01-0.44, = 0.007). Carriers of rs1801321 TT genotype were more likely to have higher NYHA class in univariable (OR = 10.0; 95% CI = 1.63-61.33; = 0.013) and multivariable (OR = 9.27; 95% CI = 1.28-67.02; = 0.027) analysis. Carriers of rs12593359 GG genotype were less likely to have higher NYHA class in univariable (OR = 0.09; 95% CI = 0.01-0.79; = 0.030) and multivariable (OR = 0.07; 95% CI = 0.01-0.81; = 0.034) analysis. Carriers of rs1799794 GG genotypes experienced more skin adverse events based on LENT-SOMA scale in univariable (OR = 5.83; 95% CI = 1.22-28.00; = 0.028) and multivariable (OR = 10.90; 95% CI = 1.61-73.72; = 0.014) analysis. In conclusion, and polymorphisms might contribute to RT adverse events in early HER2-positive breast cancer patients.