The single nucleotide polymorphisms of the XRCC3 gene including rs1799794 affect the DNA double-strand break/repair. Therefore, it plays a critical part in the initiation of carcinogenesis. This study aimed to investigate the distribution of rs1799794 and the association between rs1799794 and breast cancer risk. The study was performed in 208 Vietnamese females suffering from breast cancer and 208 age-matched normal healthy controls. DNA was extracted from whole blood whilst genotyping was conducted using PCR-RFLP. The results show that the frequency of the A and G allele in the case group are 0.575 and 0.425, in the control group are 0.548 and 0.452. The frequency of AA, AG, GG genotype in the case group are 34.6, 45.7, and 19.7%; in the control group are 33.2, 43.3, and 23.5%. AG genotype of rs1799794 associated with disease onset early of breast cancer, increasing the risk of breast cancer among those who were 45 years old and younger. The GG genotype has protective effects and reduces the risk of breast cancer in the age group ≤45 years.
