Evaluation of vitamin E and selenium supplementation for the prevention of bladder cancer in SWOG coordinated SELECT

Epidemiological and biological evidence suggests a preventive effect of selenium and vitamin E on bladder cancer. We assessed the effect of selenium and/or vitamin E on bladder cancer development.

This was a secondary analysis of the randomized, placebo controlled SELECT (Selenium and Vitamin E Cancer Prevention Trial), which included 34,887 men randomly assigned to 4 groups (selenium, vitamin E, selenium plus vitamin E and placebo) in double-blind fashion between August 22, 2001 and June 24, 2004. The primary end point was bladder cancer incidence, as determined by routine clinical management.

During a median followup of 7.1 years (IQR 6.4-8.0) 224 bladder cancer cases were recorded. Patients with bladder cancer were older, and more likely to be white and have a smoking history than those without bladder cancer. Most cancers were urothelial and nonmuscle invasive. There was no significant difference in the bladder cancer incidence between the 53 men in the placebo group and the 56 in the vitamin E group (HR 1.05, IQR 0.64-1.73, p=0.79), the 60 in the selenium group (HR 1.13, 0.70-1.84, p=0.52) or the 55 in the vitamin E plus selenium group (HR 1.05, 0.63-1.70, p=0.86).

This secondary analysis showed no preventive effect of selenium or vitamin E alone or combined on bladder cancer in this population of men. Further studies are needed to assess the effect in women, and at different doses and formulations.