Treatment With B Vitamins and Incidence of Cancer in Patients With Previous Stroke or Transient Ischemic Attack Results of a Randomized Placebo-Controlled Trial

Background and Purpose—To determine the effect of B vitamin treatment on the incidence of cancer among patients with stroke or transient ischemic attack. Methods—A total of 8164 patients with recent stroke or transient ischemic attack were randomly allocated to double-blind treatment with 1 tablet daily of placebo or B vitamins (2 mg folic acid, 25 mg vitamin B6, 500 μg vitamin B12) and followed for a median of 3.4 years for any cancer as an adverse event. Results—There was no significant difference in the incidence of any cancer among participants assigned B vitamins compared with placebo (4.04% versus 4.59%; risk ratio, 0.86; 95% CI, 0.70–1.07) and no difference in cancer mortality (2.35% versus 2.09%; risk ratio, 1.09; 0.81–1.46). Among 1899 patients with diabetes, the incidence of cancer was higher among participants assigned B vitamins compared with placebo (5.35% versus 3.28%; adjusted risk ratio, 2.21; 1.31–3.73), whereas among 6168 patients without diabetes, the incidence of cancer was lower among...