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 participants assigned B vitamins compared with placebo (3.66% versus 5.03%; adjusted risk ratio, 0.67; 0.51–0.87; P for interaction=0.0001).
Conclusions—Daily administration of folic acid, vitamin B6, and vitamin B12 to 8164 patients with recent stroke or transient ischemic attack for a median of 3.4 years had no significant effect, compared with placebo, on cancer incidence or mortality. However, a post hoc subgroup analysis raises the hypothesis that folic acid treatment may increase the incidence of cancer among diabetics and reduce the incidence of cancer among nondiabetics with a history of stroke or transient ischemic attack.
- Received October 17, 2011.
- Revision received January 17, 2012.
- Accepted February 9, 2012.
- © 2012 American Heart Association, Inc.