SELECT trial was conducted to investigate the benefits of Selenium and vitamin E in cancer.Research studies conducted in late 1990s and early 2000 pointed towards benefit of selenium and vitamin E in the prevention of prostate cancer.
In the Nutritional Prevention of Cancer Trial conducted from 1996 it was found that men taking this mineral had 52% less chances of acquiring prostate cancer than participants taking placebo.In another study conducted on 29,000 plus smokers in Finland
men taking vitamin E had 32% less chances of acquiring prostate cancer than persons taking placebo.These studies formed the basis for taking up this massive SELECT trial.
SELECT trial: Selenium and Vitamin E Cancer Prevention TrialA large comprehensive trial with supplements of selenium and vitamin E was needed to substantiate the earlier research findings which were not primarily on prostate cancer.
The primary goal of the experiment was to assess the effect on the number fresh cases of prostate cancer diagnosed during the trial.
The objective of the trial was to determine whether either or both could prevent tumor of prostate gland and other diseases with no toxicity in healthy men.
SELECT trial was also to assess the impact of vitamin E and selenium on colon and lung cancers as well as to collect the details of total incidences and survival rate.
The trial was also to study the associations between diet, food habits and cancer and provide basis for study of the molecular genetics.
A biorepository was created and the blood samples collected from participants at their entry into the trial and again after five years are to be used in studies of prostate and other cancers, and other age related diseases.Additionally, it has been examining the effect of both vitamin E and selenium supplements on quality of life of participant, and findings from these follow ups will be presented in a future announcement or publication of trial.
SELECT trial salient features: selenium and vitamin E utilityThe trial is primarily funded by NCI (National Cancer Institute) and the trial is coordinated by a network of international research organisations, SWOG (Southwest Oncology Group) which receive funding from NCI.
SELECT trial was a well designed, well monitored and well controlled randomized double-blind study.
Between August 22, 2001, and June 24, 2004, 35,533 men were enrolled.
Later due to various reasons 630 were excluded from the analysis of trial.
African Americans aged 50 years and above and other men aged 55 years and above were enrolled for SELECT trial as most of prostate cancer occurs in persons above 55 years.
Men having benign prostate hyperplasia (BPH - enlargement of prostate) were also enrolled for selenium SELECT trial, but this information and medication taken were recorded.
Only men with negative results for the prostate tests, prostate-specific antigen (PSA) test and digital rectal examination (DRE) were enrolled for SELECT trial.
Persons with uncontrolled high blood pressure were not enrolled as a dose of 400 mg or above of vitamin E may precipitate stroke in them.
At the entry stage of SELECT toenail clippings were collected to know the selenium status of the trial participants.
Blood samples were also taken on enrollment and again after five years of joining the trial to assess the vitamin E status.
The diet details were recorded but the SELECT participants were not required to change their diets.
Multivitamin tablets (without selenium and vitamin E) were offered during the trial period.
The participants were assigned randomly at 427 participating sites in Canada, Puerto Rico and United States.
The SELECT trial participants were assigned to four groups receiving vitamin E and selenium, two placebos, a placebo and the mineral or a placebo and vitamin E.
Two types of capsules were given one looking like selenium capsule and the other looking like vitamin E capsule, which contained either the supplement or a placebo.
It was a double blind study and neither the participant nor the researchers know who received the mineral, vitamin E or placebo.
However the participants will be informed of the type of supplement given to them during their study site visit in 2010.
200 micrograms (μg) of selenium as L-selenomethionine and 400 milligrams (mg) of vitamin E as dl-alpha-tocopheryl acetate were given per day.
Apart from prostate cancer, SELECT evaluated the effect of the supplements on Alzheimer's Disease, dementia, Age-related macular degeneration (AMD), cataract and loss of lung function related to aging.
This trial was initially planned for a period of 7 - 12 years, but the supplements were stopped in October 2008 due to inefficiency of the supplements in prevention.The participants are being followed up and the follow-up is to continue for 5 more years.
The results of SELECT trial: selenium and vitamin E lack cancer prevention benefitMost of the prostate cancer detected during the trial period were of early stage as well as of low grade and the stage and grade were similar between all groups.
At 5 years there were 3.8% death of SELECT participants and the number of death for each cause were similar for all groups.
There was a non significant rise of type 2 diabetes mellitus among the selenium only group.
There was a non significant rise of prostate cancer among the vitamin E only group.
The Data and Safety Monitoring Committee of SELECT programme reviewed the case study on October 29, 2008 and instructed its 35,000 plus trial participants to stop taking the selenium and vitamin E supplements.
SELECT trial showed apparent lack of health benefit over five years.
The advice of the committee was to stop the mineral and vitamin E supplements and not the trial.
It was found in SELECT that antioxidants vitamin E and trace mineral did not prevent prostate cancer when either taken alone or together for five years.
Conclusions and follow up of SELECT trial
It was decided to monitor the health of participants for three more years to determine whether there is any cancer prevention benefit or harm.
The Data and Safety Monitoring Committee of SELECT trial observed that there may be a small chance of effects of the selenium and vitamin E supplements later in participants lives.
Antioxidant function - selenoproteins.
Prevention of HIV and AIDS.
Treatment of Keshan disease.
Thyroid gland and hormones.
Selenium for prostate cancer.
Selenium health benefits.
Deficiency and symptoms.
Selenium and SELECT trial (current topic).