Selenium in treatment of men with HG-PIN to prevent prostate cancer


The SELECT study has previously shown that treatment with selenium did not prevent prostate cancer in your average “guy in the street.” However, what about men with a prior diagnosis of high-grade prostatic intraepithelial neoplasia (HG-PIN)?

HG-PIN is thought to be a potential premalignant lesion suggestive of an increased risk for prostate cancer. There has been more than a little evidence to suggest that some sort of preventive care might be able to affect the occurrence of prostate cancer in men with HG-PIN. There is also evidence that selenium supplementation may be able to have such a protective effect. 

Marshall et al. have now published the results of SWOG 9917 — a randomized, double-blind, placebo-controlled trial of selenium in men with HG-PIN. This multi-center trial was coordinated by the Southwerst Oncology Group, which enrolled over 600 patients between about 2000 and 2006. The patients all received a daily dose of 200 μg of selenomethionine. The primary endpoint of the study was progression of HG-PIN to prostate cancer over a 3-year period.

Here are the key results of the study:

  • 619 men were initially enrolled in the study.
  • 423/619 men were actually shown to have HG-PIN on central pathology review, were randomized to selenomethionine or placebo, and were eligible for inclusion in the primary study data analysis.
    • 212/423 men were treated with selenomethionine (at 200 μg/day).
    • 211/423 men were treated with placebo.
  • At 3 years of follow-up
    • 35.6 percent of patients treated with selenomethionine had been diagnosed with prostate cancer.
    • 36.6 percent of patients treated with placebo had been diagnosed with prostate cancer.
    • 70.8 percent of patients treated with selenomethionine who were diagnosed with prostate cancer had a Gleason score of ≤ 6.
    • 75.5 percent of patients treated with placebo who were diagnosed with prostate cancer had a Gleason score of ≤ 6. 
    • There was a reduced risk for diagnosis of prostate cancer in patients treated with selenomethionine vs. placebo in a subset of patients with a baseline selenium level of < 106 ng/ml (but this reducation was not statistically significant).

Clearly, treatment of men with HG-PIN does not prevent diagnosis of prostate cancer better than a placebo within 3 years in most men with HG-PIN.

The authors conclude that the 36 percent occurrence of a diagnosis of prostate cancer in these two groups of men initially diagnosed with HG-PIN does confirm that men initially diagnosed with HG-PIN are at significant risk for a subsequent diagnosis of prostate cancer within 3 years. They do not, however, conclude that such a diagnosis necessarily implies the presence of clinically significant prostate cancer.

They further conclude that any future study of the use of selenium or selenomethionine in patients a high risk for a future diagnosis of prostate cancer should focus on selenium-deficient men and selenium pharmacogenetics.

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