Selenium en vitamine E bij kanker

Binnen de orthomoleculaire behandelingen van kanker speelt selenium van oudsher een grote rol. In de VS werd begin December 2008 bekend gemaakt dat noch selenium, noch vitamine E kanker kon voorkomen bij gezonde mannen. De resultaten van de Selenium and Vitamin E Cancer Prevention Trial [SELECT]slaan een wig in de orthomoleculaire geneeskunde. De studie werd namelijk uitgevoerd bij een enorm groot aantal gezonde mannen, en de kans dat we hier te maken hebben met een vals negatieve uitkomst is erg klein. Het ging om een studie met meer dan 35000 gezonde mannen van boven de 50. Deze kregen of selenium, of vitamine E of een placebo, of een combinatie van beide actieve substanties voor tenminste 7 jaar! De conclusie was:

In conclusion, SELECT has definitively demonstrated that selenium, vitamin E, or selenium + vitamin E (at the tested doses and formulations) did not prevent prostate cancer in the generally healthy, heterogeneous population of men in SELECT. These data underscore the prudence that is needed in considering recommendations to use agents for the prevention or control of disease in the absence of convincing clinical trial results. These findings also compel the medical research community to continue the search for new, effective agents for prostate cancer prevention.

(Bron: JAMA. 2009;301(1):(doi:10.1001/jama.2008.864). 

Het commentaar van de JAMA is waard te citeren:

In 1996, a wave of hope arose when the Nutritional Prevention of Cancer trial reported a 65% reduction in prostate cancer incidence in men receiving selenium supplementation.1 This came only 2 years after the ATBC (-Tocopherol, Beta Carotene) Cancer Prevention Trial had reported a 35% reduction in prostate cancer occurrence among men taking vitamin E supplements.2 Suddenly, it appeared to make sense that this cancer could be prevented by bolstering antioxidant defenses in middle-aged and older men. Prostate cancer was not a prespecified end point in either trial, and although both results were based on post hoc analysis, randomization had worked and it seemed unlikely that the encouraging findings were due to confounding bias. Indeed, confounding stood as the likely explanation for discordance between the earlier beta carotene trials that failed to demonstrate any benefit and numerous observational studies reporting that men who consumed beta carotene–containing foods were at lower risk for developing cancer, particularly those of the respiratory tract.

Now, 12 years later, comes the disappointing news that 2 major trials conceived during the wave of hope found that neither selenium nor vitamin E supplementation, alone or in combination, produced any reductions in prostate cancer or cancer of any type. The results of these important studies, the SELECT (Selenium and Vitamin E Cancer Prevention Trial) by Lippman and colleagues and the Physicians’ Health Study (PHS) II by Gaziano and colleagues, are reported in this issue of JAMA.

Despite the null findings, it is important to recognize what these trials have accomplished. SELECT had a simple, cost-effective design, completed accrual of more than 35 000 participants ahead of schedule—making it the largest individually randomized cancer prevention trial ever conducted—and maintained high rates of adherence and retention for 4 to 7 years. Given its statistical power, it is unlikely that the study missed detecting a benefit of even a very modest size.  

(Bron:JAMA. 2009;301(1):(doi:10.1001/jama.2008.863). 

Orthomoleculaire behandeling kanker aan revisie toe

Hiermee lijkt een lange geschiedenis van pro-antioxidanten-pleiters en vitamine- adepten afgesloten. Er is geen bewijs dat inname van geisoleerde vitamines of mineralen/supplementen bij kanker preventief of therapeutisch werkzaam is. Deze grote studies die in de laatste maand van 2008 beschikbaar gekomen zijn, steunen de orthomoleculaire benadering van kanker met het geven van supplementen niet. Het is dus zinloos om bij kanker dure supplementen in te nemen, en er zijn steeds meer aanwijzingen dat geisoleerde vitamines meer kwaad kunnen dan goed doen.

Zo blijkt vitamine C bijvoorbeeld de werkzaamheid van een aantal anti-kanker middelen negatief te beinvloeden!

Verder lezen 

Vitamin C and Chemotherapy by Carolyn J. Hildreth, in JAMA. 2008;300(21):2476 

Vitamins E and C in the Prevention of Prostate and Total Cancer in Men: The Physicians’ Health Study II Randomized Controlled Trial Published December 9, 2008.  

Effect of Selenium and Vitamin E on Risk of Prostate Cancer and Other Cancers: The Selenium and Vitamin E Cancer Prevention Trial (SELECT) Published December 9, 2008.  

Randomized Trials of Antioxidant Supplementation for Cancer Prevention: First Bias, Now Chance—Next, Cause Published December 9, 2008.