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Vitamin E and the Risk of Prostate Cancer The Selenium and Vitamin E Cancer Prevention Trial (SELECT) Klein, Thompson, Tangen, et al. J Amer Med Assoc,

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Presentation on theme: "Vitamin E and the Risk of Prostate Cancer The Selenium and Vitamin E Cancer Prevention Trial (SELECT) Klein, Thompson, Tangen, et al. J Amer Med Assoc,"— Presentation transcript:

1 Vitamin E and the Risk of Prostate Cancer The Selenium and Vitamin E Cancer Prevention Trial (SELECT) Klein, Thompson, Tangen, et al. J Amer Med Assoc, Oct 12, 2011; Vol 306, No.14; Zachary Lapaquette PharmD Candidate University of Georgia

2 Background 16% of men will be diagnosed with prostate cancer in their lifetime 1 Most common type of cancer in U.S. men, other than non-melanoma skin cancer 2 Second leading cause of cancer-related death in U.S. men

3 Background Vitamin E is fat-soluble and has anti-oxidative properties Recommended daily allowance for vitamin E is 22.4IU (15mg) daily 3 Doses of 50IU/day were shown to decrease prostate cancer incidence in smokers 4

4 SELECT Trial Randomized, placebo-controlled, multi-center trial Compared selenium 200mcg/day, vitamin E 400IU/day, or both against placebo Planned follow-up minimum of 7 years and maximum of 12 years

5 Inclusion Criteria Healthy Age 50 or older for African Americans, or 55 for all other men No h/o prostate cancer diagnosis PSA < 4ng/mL Normal DRE No current use of anticoagulants No h/o hemorrhagic stroke Normal blood pressure

6 Methods Participants without prostate cancer had clinic visits every 6 months; with prostate cancer, annually Annual PSA and DRE were not mandatory Prostate cancer status was determined by self- report at each 6-month visit Pathology report, tissue then sent to SELECT

7 Methods Study was blinded until 10/23/2008, when participants discontinued use of study agents Non-blinded follow-up occurred until 07/2011

8 Statistical Analysis Primary end point: Prostate cancer incidence as determined by routine clinical management Other areas of study: colorectal cancer, lung cancer, all other primary cancers, deaths (all cause), development of diabetes, CVE 1- and 2-sided P values given

9 Statistical Analysis Proportional hazards model used Unlike linear regression, proportional hazards models do not assume normal distribution and allow for censored data Men without end-point of interest were censored at last contact date Chi-squared test used to test the difference in the relative risk of diabetes

10 Results Total of 35,533 men randomized at 427 centers into placebo (n=7594 had final follow-up data), vitamin E (n=7650), selenium (n=7626), selenium +vitamin E (n=7620) No significant differences in age, race, baseline PSA, or diagnostic testing

11 Results Placebo (n=8696) Vitamin E (n=8737) Selenium (n=8752) Vitamin E + Selenium (n=8702) No. of prostate cancers Hazard ratio (99% CI) 1.17 ( )1.09 ( )1.05 ( ) P value Absolute Risk Gleason >7, No Hazard Ratio (99% CI) 1.16 ( )1.21 ( )1.23 ( ) P value

12 Results Placebo (n=8696) Vitamin E (n=8737) Selenium (n=8752) Vitamin E + Selenium (n=8702) All cancers Hazard ratio (99% CI) 1.07 ( )1.02 ( P value Diabetes Relative risk (99% CI) 1.05 ( )1.04 ( )0.99 ( ) P value

13 Authors Comment An explanation for the increased risk of prostate cancer in the vitamin E arm is not apparent The insignificant increased risk in the vitamin E + selenium arm implies that selenium may have a protective effect This study is seems to contradict ATBC and PHS II studies Caution should be used when recommending or studying high doses of micronutrients Health effects from these agents may continue even after the intervention is stopped

14 Conclusion Healthy men with average risk of prostate cancer subjected to contemporary community standards of screening and biopsy who took a common dose of vitamin E have a significantly increased risk of prostate cancer. The increased risk implies that seemingly innocuous yet biologically active substances such as vitamins can cause harm Consumers need be skeptical of health claims for unregulated over-the- counter products in the absence of strong evidence of benefit

15 Presenters Comment Study has good reach, but is limited to healthy men 50+ years old Criticism of study: Did not have best- and worst-case censure analysis Data collection dependent on self-report 427 research sites Overall strong study Placebo event rate: 529/8696 =

16 Presenters Comment NNH = 98 Vit E prostate cancer rate: 620/8737 = Placebo prostate cancer rate: 529/8696 =

17 Works Cited Klein, Thompson, Tangen, et al. Vitamin E and the Risk of Prostate Cancer: The Selenium and Vitamin E Cancer Prevention Trial. J Amer Med Assoc, Oct 12, 2011; Vol 306, No.14; National Cancer Institute. A Snapshot of Prostate Cancer. Sep National Institutes of Health. Dietary Supplement Fact Sheet: Vitamin E. Oct Heinonen et al. Prostate cancer and supplementation with alpha-tocopherol and beta-carotene: incidence and mortality in a controlled trial. J Natl Cancer Inst Mar 18;90(6):440-6.


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