RRM1 and Decreased total leukocyte count: RRM1 rs12806698 (−37C/A) was suggested as a candidate risk factor for grade 3-4 leukocytopenia (OR = 5.095; 95% CI: 2.132–12.170; p = 0.0002) and grade 3-4 neutropenia (OR = 2.561; 95% CI: 1.075–6.099; p = 0.034) in recessive model in 437 NSCLC patients (Zheng et al., 2017), while in another study of 63 NSCLC patients, grade 2-4 leukopenia was more frequent among patients with wild-type RRM1 rs12806698 CC genotype than carriers of CA genotype (37% versus 10%, p = 0.05) (Isla et al., 2004).