The Genetic Polymorphisms of DNA Repair Gene RAD51 and Their Role as a Predictive Biomarker for Breast Cancer Risk and Response to Radiotherapy in Iraqi Women.

Variation in the DNA repair gene RAD51 has been linked to breast cancer (BC), the most common cancer worldwide, raising concerns about radiotherapy (RT) resistance. This study aims to determine RAD51 levels and polymorphisms in Iraqi women with BC before and after RT and to evaluate their potential as cancer risk and treatment response biomarkers. This follow-up study examined 90 blood samples from 30 newly diagnosed BC patients aged 34-56 years before and after RT at the Al-Amal National Hospital for Cancer Management in Baghdad collected from July 2024 to January 2025, and from 30 age- and sex-matched healthy controls. In ELISA, serum RAD51 levels were estimated. RAD51 SNPs were genotyped through PCR amplification with specific primers and DNA sequencing. Post-RT, BC patients had significantly more RAD51 levels than pre-treatment patients and controls (2.51±0.70 vs. 1.22±0.19 vs. 1.27±0.21 ng/ml). The Iraqi population's rs1801320 (G>C) and rs1801321 (G>T) SNPs in exon 1 of the RAD51 were identified and recently registered at the NCBI (PV661827 and PV661828). The RAD51 (G>T) polymorphism's GT genotype and T allele were significant risk factors for BC (OR=11.07, CI=3.20-37.87 and OR=4.92, CI=1.82-13.35). BC patients had a lower variation post-RT compared to prior (20.0% vs. 27.0%). The RAD51 (G>C) polymorphism GC genotype or C allele was not linked with BC risk (OR=2.25, CI=0.50-9.93 and OR=2.11, CI=0.503-8.87, P>0.05). The Iraqi BC risk was associated with the RAD51 (G>T) polymorphism. GT genotype / T allele patients responded well to RT, indicating that RAD51 might predict cancer risk and RT effectiveness. Iraqi women may benefit from the RAD51 (G>C) GG genotype in protection against BC.