Meta-analyses of the methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and risk of head and neck and lung cancer

Authors report the results of four meta-analyses of studies that examined the association between methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and head and neck cancer (nine studies, 2076 cases and 4834 controls for C677T; four studies, 1439 cases and 3941 controls for A1298C), and lung cancer (ten studies. 5274 cases and 7435 controls for C677T; seven studies, 5098 cases and 6243 controls for A1298C). The summary odds ratio (OR) of head and neck cancer was 0.92 (95% CI: 0.76-1.11) for MTHFR 677 TT and 0.68 (95% CI: 0.37-1.26) for MTHFR 1298 CC. The OR of lung cancer was 1.22 [95% confidence interval (CI): 0.95-1.55] for MTHFR 677 TT and 1.07 (95% CI: 0.83-1.38) for MTHFR 1298 CC. Results from the meta-analysis of three studies on C677T stratified according to dietary folate intake showed an increased risk for individuals with low folate intake (OR =1.37, 95% CI: 0.92-2.06 for head and neck and OR = 1.28, 95% CI: 0.97-1.68 for lung) versus high folate intake (OR = 0.85, 95% CI: 0.63-1.16 for head and neck, and OR = 0.94, 95% CI: 0.79-1.12 for lung). Despite the lack of formal statistical significance, these findings are consistent with the hypothesis that folate play a role in lung and head/neck carcinogenesis, and show the need to incorporate data on folate intake when interpreting results of MTHFR polymorphisms in relation to cancer risk. (C) 2008 Elsevier Ireland Ltd. All rights reserved.