Tuesday, January 13, 2009

Flushing Your Money on Anti-oxidants - Another Chemoprevention Trial Bites the Dust

Effect of Selenium and Vitamin E on Risk of Prostate Cancer and Other Cancers The Selenium and Vitamin E Cancer Prevention Trial (SELECT)
Scott M. Lippman, MD; Eric A. Klein, MD; Phyllis J. Goodman, MS; M. Scott Lucia, MD; Ian M. Thompson, MD; Leslie G. Ford, MD; Howard L. Parnes, MD; Lori M. Minasian, MD; J. Michael Gaziano, MD, MPH; Jo Ann Hartline, MPH; J. Kellogg Parsons, MD, MHS; James D. Bearden III, MD; E. David Crawford, MD; Gary E. Goodman, MD; Jaime Claudio, MD; Eric Winquist, MD, MSc; Elise D. Cook, MD; Daniel D. Karp, MD; Philip Walther, MD; Michael M. Lieber, MD; Alan R. Kristal, DrPH; Amy K. Darke, MS; Kathryn B. Arnold, MS; Patricia A. Ganz, MD; Regina M. Santella, PhD; Demetrius Albanes, MD; Philip R. Taylor, MD, ScD; Jeffrey L. Probstfield, MD; T. J. Jagpal, CCRP; John J. Crowley, PhD; Frank L. Meyskens Jr, MD; Laurence H. Baker, DO; Charles A. Coltman Jr, MD
JAMA. 2009;301(1):39-51.

Context Secondary analyses of 2 randomized controlled trials and supportive epidemiologic and preclinical data indicated the potential of selenium and vitamin E for preventing prostate cancer.
Objective To determine whether selenium, vitamin E, or both could prevent prostate cancer and other diseases with little or no toxicity in relatively healthy men.
Design, Setting, and Participants A randomized, placebo-controlled trial (Selenium and Vitamin E Cancer Prevention Trial [SELECT]) of 35 533 men from 427 participating sites in the United States, Canada, and Puerto Rico randomly assigned to 4 groups (selenium, vitamin E, selenium + vitamin E, and placebo) in a double-blind fashion between August 22, 2001, and June 24, 2004. Baseline eligibility included age 50 years or older (African American men) or 55 years or older (all other men), a serum prostate-specific antigen level of 4 ng/mL or less, and a digital rectal examination not suspicious for prostate cancer.
Interventions Oral selenium (200 µg/d from L-selenomethionine) and matched vitamin E placebo, vitamin E (400 IU/d of all rac--tocopheryl acetate) and matched selenium placebo, selenium + vitamin E, or placebo + placebo for a planned follow-up of minimum of 7 years and a maximum of 12 years.
Main Outcome Measures Prostate cancer and prespecified secondary outcomes, including lung, colorectal, and overall primary cancer.
Results As of October 23, 2008, median overall follow-up was 5.46 years (range, 4.17-7.33 years). Hazard ratios (99% confidence intervals [CIs]) for prostate cancer were 1.13 (99% CI, 0.95-1.35; n = 473) for vitamin E, 1.04 (99% CI, 0.87-1.24; n = 432) for selenium, and 1.05 (99% CI, 0.88-1.25; n = 437) for selenium + vitamin E vs 1.00 (n = 416) for placebo. There were no significant differences (all P>.15) in any other prespecified cancer end points. There were statistically nonsignificant increased risks of prostate cancer in the vitamin E group (P = .06) and type 2 diabetes mellitus in the selenium group (relative risk, 1.07; 99% CI, 0.94-1.22; P = .16) but not in the selenium + vitamin E group.
Conclusion Selenium or vitamin E, alone or in combination at the doses and formulations used, did not prevent prostate cancer in this population of relatively healthy men.
BrooklynDodger(s) comment: Many would hope that cancer could be prevented by eating your vegetables or taking stuff from the health food store. Lots easier than preventing exposure to carcinogens. There's a loose hypothesis that anti-oxidants prevent cancer, since some oxidants cause cancer.

So, somebody funded a 35,000 person cohort. Imagine the industrial cohorts which could have been studied to that!!

Those continuing proponents of chemoprevention could argue that the observation period was only 5 years, so the effect would only be on pre-enrollment tumors. If vitamin E is good for you, it would also be good for tumor cells.

The Dodger(s) continue to hope in vain for funding on true prevention, which would identify chemical risks. On the other hand, it's good to see some interest in prostate cancer, which kills as many as breast cancer, but has no lobby.

[By the way, "flushing" in the title is meant to evoke some connection to urinary problems associated with BPH]

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