CYP2D6 and cancer: The present study was conducted in a larger population (n = 541) and investigated other genetic variants affecting the efficacy and safety of anti-cancer drugs such as CYP2D6 (rs1065852:c.100 C > T), DPYD (rs3918290: c.1905 + 1G > A and rs56038477:c.1236G > A), EPAS1 (rs7557402:c.1035–7 C > G), and NUDT15*3 (rs116855232:c.415 C > T), in addition to the XRCC1 (rs25487:c.1196 A > G) variant.