title: Treatment with B vitamins and incidence of cancer in patients with previous stroke or transient ischemic attack: results of a randomized placebo-controlled trial.
abstract: OBJECTIVE
  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 B(6), 500 μg vitamin B(12)) 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 B(6), and vitamin B(12) 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.
authors.affiliation: FRACP, Department of Neurology, Royal Perth Hospital, 197 Wellington Street, Perth, Australia 6001.   gjhankey@cyllene.uwa.edu.au.
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: Hankey
authors.forename: John W
authors.initials: JW
authors.lastname: Eikelboom
authors.forename: Qilong
authors.initials: Q
authors.lastname: Yi
authors.forename: Kennedy R
authors.initials: KR
authors.lastname: Lees
authors.forename: Christopher
authors.initials: C
authors.lastname: Chen
authors.forename: Denis
authors.initials: D
authors.lastname: Xavier
authors.forename: Jose C
authors.initials: JC
authors.lastname: Navarro
authors.forename: Udaya K
authors.initials: UK
authors.lastname: Ranawaka
authors.forename: Wasim
authors.initials: W
authors.lastname: Uddin
authors.forename: Stefano
authors.initials: S
authors.lastname: Ricci
authors.forename: John
authors.initials: J
authors.lastname: Gommans
authors.forename: Reinhold
authors.initials: R
authors.lastname: Schmidt
mesh_terms: D004311:Double-Blind Method; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000150:complications / Q000401:mortality*; D008297:Male; D009369:Neoplasms / Q000401:mortality* / Q000517:prevention & control; D020521:Stroke / Q000150:complications / Q000401:mortality*; D014803:Vitamin B Complex / Q000008:administration & dosage*
chemical_list: D014803:Vitamin B Complex