Only Puerta-García et al. (European ancestry; Spain) reported a significant association of the TT genotype of the MTHFR rs1801133 SNP (c.665C>T; missense; p.Ala222Val) with the risk of asthenia in 84 patients with CRC (stages I–IV) receiving first-line treatment with adjuvant capecitabine (OR = 9.30; 95% CI = 1.36–106.8; p = 0.009 for TT vs. CT/CC) [31]. This evidence concerns the gene MTHFR and colorectal carcinoma.