title: A randomized, 12-year primary-prevention trial of beta carotene supplementation for nonmelanoma skin cancer in the physician's health study.
abstract: BACKGROUND
  Although basic research provides plausible mechanisms for benefits of beta carotene supplementation on nonmelanoma skin cancer (NMSC) primarily consisting of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), observational studies are inconsistent. Randomized trial data are limited to 1 trial of secondary prevention that showed no effect of beta carotene on the incidence of NMSC after 5 years.
  
  
  OBJECTIVE
  To test whether supplementation with beta carotene reduces the risk for development of a first NMSC, including BCC and SCC.
  
  
  METHODS
  Randomized, double-blind, placebo-controlled trial with 12 years of beta carotene supplementation and follow-up.
  
  
  METHODS
  Physicians' Health Study in the United States.
  
  
  METHODS
  Apparently healthy male physicians aged 40 to 84 years in 1982 (N = 22 071).
  
  
  METHODS
  Beta carotene, 50 mg, on alternate days.
  
  
  METHODS
  Relative risk (RR) and 95% confidence interval (CI) for a first NMSC, BCC, and SCC.
  
  
  RESULTS
  After adjusting for age and randomized aspirin assignment, there was no effect of beta carotene on the incidence of a first NMSC (RR, 0.98; 95% CI, 0.92-1.05), BCC (RR, 0.99; 95% CI, 0.92-1.06), or SCC (RR, 0.97; 95% CI, 0.84-1.13). There was also no significant evidence of beneficial or harmful effects of beta carotene on NMSC by smoking status (current, past, or never).
  
  
  CONCLUSIONS
  This large-scale, randomized, primary prevention trial among apparently healthy well-nourished men indicates that an average of 12 years of supplementation with beta carotene does not affect the development of a first NMSC, including BCC and SCC.
authors.affiliation: Division of Preventive Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass, USA.
authors.forename: U M
authors.initials: UM
authors.lastname: Frieling
authors.forename: D A
authors.initials: DA
authors.lastname: Schaumberg
authors.forename: T S
authors.initials: TS
authors.lastname: Kupper
authors.forename: J
authors.initials: J
authors.lastname: Muntwyler
authors.forename: C H
authors.initials: CH
authors.lastname: Hennekens
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000627:therapeutic use*; D002280:Basal Cell Carcinoma / Q000453:epidemiology / Q000517:prevention & control*; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology / Q000517:prevention & control*; D015331:Cohort Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011322:Primary Prevention; D012878:Skin Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D014481:United States / Q000453:epidemiology; D019207:beta Carotene / Q000627:therapeutic use*
chemical_list: D000975:Antioxidants; D019207:beta Carotene