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Prostate Cancer Prevention

Last Revised August 24, 1995

Introduction | The Prostate Cancer Prevention Trial | Why should finasteride prevent prostate cancer development? | Where can you find more information?


The major increase in the number of cases of prostate cancer identified in recent years has led researchers to consider the possibility of preventing prostate cancer development in selected individuals at highest risk of this disease. The availability of new pharmaceuticals with relatively minor side effects has also helped allow researchers to carry out careful investigation of this possibility.

The Prostate Cancer Prevention Trial

The Prostate Cancer Prevention Trial (PCPT) was organized by the National Cancer Institute in 1993 as the first ever large-scale trial for the prevention of prostate cancer in the USA. It is designed to test whether a pharmaceutical known as finasteride or Proscar (made by Merck & Co.) will prevent men from developing prostate cancer.

This trial will involve 18,000 men who are at least 55 years old. The minimum age limit of 55 was chosen because older men are much more likely to develop prostate cancer than young men. According to the National Cancer Institute, of every 100 cases of prostate cancer discovered, 98 are in men over 55 years of age.

The 18,000 men who take part in this trial will be divided into two groups at random. Half the men (about 9,000) will be asked to take one finasteride tablet per day for 7 years. The other 9,000 men will be asked to take a placebo tablet every day for 7 years. A placebo is an inactive tablet that looks exactly like the active tablet in the trial (in this case finasteride). However, none of the men in the trial, or their doctors, will know whether an individual patient is taking finasteride or the placebo. This system is known as "double blinding" and means that there is the highest possible chance that the results of the trial will not be affected by the individual knowledge of trial participants or their personal physicians. At various times, the two groups of men will be compared to see if there is any difference between the rates of prostate cancer development in the two groups.

We had previously reported information suggesting that this trial is not enrolling patients as fast as was hoped, and also that patients were dropping out of the trial at an unexpectedly high rate. We are delighted to report that this is not the case. Accrual and randomization of patients to this trial are in fact above the requirements originally projected, and drop-out rates are within the expected limits. Additional information is available in a Letter to the Editor from Phyllis Goodman, the lead statistician working on this trial.

Why should finasteride prevent prostate cancer development?

There is no absolute proof that finasteride can prevent the development of prostate cancer -- even in laboratory animals. However, the way in which finasteride works -- also called its mechanism of action -- means that it has certain effects which could lower the risk of men developing clinically evident prostate cancer within a specific time period. For example, finasteride can reduce the level of a hormone known as dihydrotestosterone or DHT in the prostate, and we know that DHT is important in the development and growth of prostate cancer.

The really important reason why finasteride is the first pharmaceutical ever to be tested in a large clinical trial for prevention of prostate cancer is that it appears to have an exceptionally low level of side effects. According to most authorities, even those side effects that have been documented are comparatively mild. In this trial, an active pharmaceutical is being given to men who are perfectly healthy. This means that the pharmaceutical (finasteride) must be as safe as possible, so that the risks associated with taking the pharmaceutical for seven years are very little more than the risks associated with taking the inactive placebo.

Where can you find more information?

There is a considerable amount of information available about the Prostate Cancer Prevention Trial. In the first place, many physicians across the country are actively involved in helping to enroll patients into this trial. If you think that you might like to participate in this trial, the first step would be to ask your personal physician if he or she can give you further information.

Additional information is also available at the following on-line sites:
button Questions and Answers About the Prostate Cancer Prevention Trial
button Prostate Cancer Prevention Trial Will Recruit 18,000 Men

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The content in this section of the Phoenix 5 site was originally developed by CoMed Communications (a Vox Medica company) as part of The Prostate Cancer InfoLink. It is reproduced here with the permission of Vox Medica.

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