「ビタミンEは前立腺癌の発生を増加させるかもしれない」
という論文が掲載されました。JAMA. 2011;306:1549-1556
35,533人を対象に行われたSELECT試験の結果です。
ビタミンE単独摂取は1.17倍前立腺癌の発生リスクが統計学的有意に増加するとのこと。
ビタミンサプリメントを摂取している人は注意を。
Study Highlights
Men eligible for study participation were at least 50 years old (for black men) or 55 years old (for all other participants) and had a prostate-specific antigen (PSA) value of 4.0 ng/mL or less. They also had normal digital rectal examination for prostate cancer.
Participants were randomly assigned to 1 of 4 placebo-controlled treatment groups: selenium 200 µg/day, vitamin E 400 IU/day, both selenium and vitamin E, or double placebo.
Participants underwent a limited history and physical examination every 6 months during the study and were encouraged to receive prostate cancer screening according to the community standard.
The main study outcome was incident prostate cancer. Researchers also followed the incidence rates of other types of cancer, along with incident type 2 diabetes mellitus and cardiovascular disease.
Active study treatment was discontinued after approximately 5.5 years.
35,533 men underwent randomization between 2001 and 2004. The median age of men was 63 years, and nearly 80% of participants were white. The mean PSA level at baseline was 1.1 ng/mL.
The current report provides another 54,464 person-years of follow-up. There was no difference regarding the intensity of PSA testing during follow-up in comparing the study intervention groups.
521 additional prostate cancers were recorded since the initial report. Treatment with vitamin E was associated with a significant increase in the risk for prostate cancer (hazard ratio, 1.17; 99% confidence interval, 1.004 - 1.36).
However, treatment with selenium alone or selenium plus vitamin E was not associated with a significant change in the risk for prostate cancer.
Gleason 6 prostate cancer was the most common cancer grade overall. However, the association between vitamin E and the risk for prostate cancer appeared to span the spectrum of cancer grades.
The difference in the risk for prostate cancer between vitamin E and placebo became apparent by study year 3 and gradually increased thereafter, including after the discontinuation of active treatment.
Selenium was not associated with a significant change in the risk for incident type 2 diabetes during the longer follow-up period. There were no other significant associations between study treatments and the risks for types of cancer other than prostate cancer, or in the risks for cardiovascular events or overall mortality.
From Medscape Education Clinical Briefs
JAMA. 2011;306:1549-1556.