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The Role of PC-SPES, Selenium, and Vitamin E in Prostate Cancer

The Role of PC-SPES, Selenium, and Vitamin E in Prostate Cancer

The use of complementary and alternative medicine is a
well-known phenomenon among cancer patients, and prostate cancer patients are no
exception. The review article by Drs. Das and Kaplan nicely summarizes most of
the data available on the use of PC-SPES, selenium, and vitamin E by prostate
cancer patients. These three agents are probably the most widely used
complementary approaches in prostate cancer, and they are the ones that have
been studied most extensively. However, true data on efficacy, careful toxicity
analyses, dose-response analysis, or pharmacokinetic analyses of these agents
are extremely limited.

Perhaps the article’s first lesson is that the use of complementary and
alternative medicine among prostate cancer patients is increasing. It is hard to
know exactly what percentage of patients use these therapies, although the exact
percentage probably depends on the sample surveyed. Support groups, urology
practices, and tertiary referral centers may include a larger proportion of
patients who have explored the use of complementary medicine.

In any case, this article points out that it behooves us to take a careful
medical history from our patients because published series suggest that
one-third or more of prostate cancer patients use some form of complementary
medicine. At our institution, for example, we no longer ask patients, "What
medicines are you taking?" We ask specifically, "Are you taking any
supplements, vitamins, herbal products, or other over-the-counter
compounds?" A comprehensive questionnaire listing the most commonly used
agents is useful to this end.

Confounding Variables

Why should we care what over-the-counter products our patients take? First,
we should not assume that these compounds are benign. (And even if they have not
caused any adverse events as single agents, they essentially represent black
boxes that may interact with other prescribed or nonprescribed medications.)
Second, as we evaluate the efficacy of novel therapeutics for patients, we need
to know if any confounding variables exist.

For example, we now know that PC-SPES is capable of modulating the expression
of prostate-specific antigen (PSA) in virtually all patients with
hormone-sensitive disease and a majority of patients with hormone-refractory or
androgen-independent disease. If use of a novel agent is initiated and we are
unaware that the patient has also recently started taking PC-SPES, we and our
patients are blinded as to which agent or combination of agents is, in fact,
providing clinical benefit.

This article provides physicians with a useful tool for discussing with their
patients what is known about the use of PC-SPES, vitamin E, and selenium. In
addition to the authors’ conclusion that it is extremely important that
physicians and other health-care professionals understand the potential role and
side effects of these therapies, the importance of relaying this information to
patients as nonjudgmentally and objectively as possible also needs to be
emphasized.

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