title: Beta-carotene antioxidant use during radiation therapy and prostate cancer outcome in the Physicians' Health Study.
abstract: OBJECTIVE
  The safety of antioxidant supplementation during radiation therapy (RT) for cancer is controversial. Antioxidants could potentially counteract the pro-oxidant effects of RT and compromise therapeutic efficacy. We performed a prospective study nested within the Physicians' Health Study (PHS) randomized trial to determine if supplemental antioxidant use during RT for prostate cancer is associated with an increased risk of prostate cancer death or metastases.
  
  
  METHODS
  PHS participants (383) received RT for prostate cancer while randomized to receive beta-carotene (50 mg on alternate days) or placebo. The primary endpoint was time from RT to lethal prostate cancer, defined as prostate cancer death or bone metastases. The Kaplan-Meier method was used to estimate survival probabilities and the log-rank test to compare groups. Cox proportional hazards regression was used to estimate the effect of beta-carotene compared with that of placebo during RT.
  
  
  RESULTS
  With a median follow-up of 10.5 years, there was no significant difference between risk of lethal prostate cancer with the use of beta-carotene during RT compared with that of placebo (hazard ratio = 0.72; 95% confidence interval [CI], 0.42-1.24; p = 0.24). After we adjusted for age at RT, prostate-specific antigen serum level, Gleason score, and clinical stage, the difference remained nonsignificant. The 10-year freedom from lethal prostate cancer was 92% (95% CI, 87-95%) in the beta-carotene group and 89% (95% CI, 84-93%) in the placebo group.
  
  
  CONCLUSIONS
  The use of supplemental antioxidant beta-carotene during RT was not associated with an increased risk of prostate cancer death or metastases. This study suggests a lack of harm from supplemental beta-carotene during RT for prostate cancer.
authors.affiliation: Harvard Radiation Oncology Program, Boston, Massachusetts, USA. dmargalit@lroc.harvard.edu
authors.forename: Danielle N
authors.initials: DN
authors.lastname: Margalit
authors.forename: Julie L
authors.initials: JL
authors.lastname: Kasperzyk
authors.forename: Neil E
authors.initials: NE
authors.lastname: Martin
authors.forename: Howard D
authors.initials: HD
authors.lastname: Sesso
authors.forename: John Michael
authors.initials: JM
authors.lastname: Gaziano
authors.forename: Jing
authors.initials: J
authors.lastname: Ma
authors.forename: Meir J
authors.initials: MJ
authors.lastname: Stampfer
authors.forename: Lorelei A
authors.initials: LA
authors.lastname: Mucci
mesh_terms: D000368:Aged; D000975:Antioxidants / Q000008:administration & dosage / Q000009:adverse effects*; D001859:Bone Neoplasms / Q000556:secondary; D002423:Cause of Death; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D060787:Neoplasm Grading; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood; D011468:Prostatectomy / Q000401:mortality; D011471:Prostatic Neoplasms / Q000097:blood / Q000401:mortality* / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D011836:Radiation Tolerance / Q000187:drug effects; D016896:Treatment Outcome; D019207:beta Carotene / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D019207:beta Carotene; D017430:Prostate-Specific Antigen
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