Background: Folate and vitamin B12 are essential for maintaining DNA integrity and may influence prostate cancer (PCa) risk, but the association with clinically relevant, advanced stage, and high-grade disease is unclear.
Objective: To investigate the associations between circulating folate and vitamin B12 concentrations and risk of PCa overall and by disease stage and grade.
Design, setting, and participants: A study was performed with a nested case-control design based on individual participant data from six cohort studies including 6875 cases and 8104 controls; blood collection from 1981 to 2008, and an average follow-up of 8.9 yr (standard deviation 7.3). Odds ratios (ORs) of incident PCa by study-specific fifths of circulating folate and vitamin B12 were calculated using multivariable adjusted conditional logistic regression.
Outcome measurements and statistical analysis: Incident PCa and subtype by stage and grade.
Results and limitations: Higher folate and vitamin B12 concentrations were associated with a small increase in risk of PCa (ORs for the top vs bottom fifths were 1.13 [95% confidence interval (CI), 1.02-1.26], ptrend=0.018, for folate and 1.12 [95% CI, 1.01-1.25], ptrend=0.017, for vitamin B12), with no evidence of heterogeneity between studies. The association with folate varied by tumour grade (pheterogeneity<0.001); higher folate concentration was associated with an elevated risk of high-grade disease (OR for the top vs bottom fifth: 2.30 [95% CI, 1.28-4.12]; ptrend=0.001), with no association for low-grade disease. There was no evidence of heterogeneity in the association of folate with risk by stage or of vitamin B12 with risk by stage or grade of disease (pheterogeneity>0.05). Use of single blood-sample measurements of folate and B12 concentrations is a limitation.
Conclusions: The association between higher folate concentration and risk of high-grade disease, not evident for low-grade disease, suggests a possible role for folate in the progression of clinically relevant PCa and warrants further investigation.
Patient summary: Folate, a vitamin obtained from foods and supplements, is important for maintaining cell health. In this study, however, men with higher blood folate levels were at greater risk of high-grade (more aggressive) prostate cancer compared with men with lower folate levels. Further research is needed to investigate the possible role of folate in the progression of this disease.
Keywords: Folate; High grade; Pooled data meta-analysis; Prospective cohort; Prostate cancer; Vitamin B(12).
Copyright © 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.