For example, in PCa patients with the combination ValAla of the antioxidant SOD2 (superoxide dismutase 2) Val16Ala SNP and ThrMet of XRCC3 Thr241Met SNP experienced a significant increase in grade 2 late rectal bleeding compared to patients without this particular genotypic arrangement11. Here, XRCC3 is linked to posterior cortical atrophy.