Variation in MTHFR defined by Ala222Val appeared to influence OS for SCLC in a recessive fashion with HR associated with heterozygote, homozygote and carrier status being 1.08 (95% CI: 0.70–1.68), 1.92 (95% CI: 1.03–3.58) and 1.20 (95% CI: 0.79–1.82), respectively. Here, MTHFR is linked to small cell lung carcinoma.