Vitamin D as Cancer Therapy?: Insights From 2 New Trials
Menés aux Etats-Unis sur 139 patients atteints d'un cancer colorectal de stade avancé ou métastatique (âge moyen : 56 ans) et sur 417 patients atteints d'un cancer des voies digestives (œsophage, estomac, colorectal ; âge moyen : 66 ans), ces deux essais randomisés évaluent l'efficacité, du point de vue de la survie sans progression et de la survie sans récidive, et la toxicité d'une supplémentation en vitamine D3
Over the past 30 years, extensive research has explored the use of nutritional supplements for prevention of cancer. Despite what appears to be strong observational evidence, randomized clinical trials of beta carotene, ascorbic acid, alpha tocopherol, selenium, and folic acid all failed to show evidence of efficacy for cancer chemoprevention. The colorectum has been particularly well studied: trials of these interventions examining adenoma recurrence have been uniformly negative as well.The latest supplement of interest is vitamin D. Observational studies have consistently found that high vitamin D status, as measured by circulating 25-hydroxyvitamin D (25[OH]D) is inversely related to the risk of colorectal cancer. However, high 25(OH)D levels may be a marker of “good health,” a trait that observational studies may not be able to fully control for in analysis. Two recent clinical trials failed to find a chemopreventive benefit of vitamin D3 supplementation. In the VITAL trial, 2000 IU/d for a median of 5.3 years did not reduce risk of all cancer or colorectal cancer. This may have been due to the short follow-up in the context of the long latent period for carcinogenesis. In another trial reported in 2015, 1000 IU/d of vitamin D3 for 3 to 5 years did not reduce adenoma recurrence, and although the follow-up period was sufficient to assess this risk, the dosage of vitamin D in that trial may have been too low.
JAMA , éditorial, 2018