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AVODART (DUTASTERIDE) & PROSTATE CANCER PREVENTION
Because most prostate cancers, like breast cancer, are fueled by sex hormones, the prevention of prostate cancer through the use of hormone-blocking medications is an attractive potential strategy.
Two medications, finasteride (Proscar) and dutasteride (Avodart), are FDA-approved to treat the benign enlargement of the prostate that commonly occurs with increasing age (also known as benign prostatic hypertrophy, or BPH). Both of these medications have recently been evaluated in prospective, randomized, placebo-controlled clinical research trials as potential prostate cancer prevention agents. Finasteride and dutasteride are 5-alpha-reductase inhibitors, and function by blocking the conversion of testosterone into dihydrotestosterone by this enzyme (dihydrotestosterone is the biologically active male sex hormone within the prostate gland). Finasteride inhibits one of the two known forms of 5-alpha-reductase, while dutasteride (Avodart) inhibits both forms.
Finasteride (Proscar) has previously been evaluated in the Prostate Cancer Prevention Trial, which enrolled nearly 19,000 men (55 years of age and older) who were without any clinical evidence of prostate cancer at the time they entered the study. These men were randomly assigned to receive either finasteride or an identical placebo pill, and the entire cohort of men was then followed for a period of 7 years. After 7 years of follow-up, 18 percent of the men who had been secretly randomized to receive finasteride were diagnosed with prostate cancer, while 24 percent of the men who had received the placebo pill (unknown to them at the time) developed prostate cancer. Thus, taking finasteride for 7 years was associated with a 25 percent reduction in the relative risk of prostate cancer during the relatively brief course of this clinical study. However, a potentially significant downside was also observed in this study, as the men who received finasteride, and who still went on to develop prostate cancer, tended to have more aggressive tumors when compared to the men in the placebo group (37 percent versus 22 percent, respectively). Moreover, and not surprisingly, since finasteride blocks the active metabolite of testosterone, sexual dysfunction and breast enlargement were more common among the men taking finasteride when compared to the men in the placebo group.
Following the intriguing results with finasteride (Proscar) in the Prostate Cancer Prevention Trial, there has been a great deal of anticipation building for results of the recently completed dutasteride (Avodart) prostate cancer prevention trial. Now, the results of this important cancer prevention study have just been published in the New England Journal of Medicine. This prospective, randomized, blinded, placebo-controlled study lasted for 4 years, and included 6,729 men at high risk of developing prostate cancer. These men, all of whom were between 50 and 75 years of age, were secretly randomized to receive either 0.5 mg of dutasteride (Avodart) per day or an identical placebo pill. As part of this research study’s protocol, all of these men underwent needle biopsies of the prostate gland at 2 years and 4 years after entering the study. By the end of the study, 20 percent of the men who had received dutasteride (Avodart) had developed prostate cancer, while 25 percent of the men in the placebo (control) group were diagnosed with prostate cancer. Thus, there was an observed 25 percent decrease in the relative risk of prostate cancer among the group of men that was randomized to receive dutasteride (Avodart) for 4 years (and a 5 percent absolute reduction in prostate cancer risk with Avodart). As was observed in the finasteride (Proscar) study, however, there was also a higher incidence of more aggressive (i.e., higher grade) tumors observed among the men who took dutasteride (Avodart) when compared to the men in the placebo group, although only a very small number of these high grade tumors were identified in either group of men. Finally, and not surprisingly, the symptoms of benign prostatic hypertrophy (BPH), including difficulties in passing urine, were much improved among the men randomized to take dutasteride (Avodart).
Because it is still too soon to determine whether or not finasteride or dutasteride are able to significantly reduce the risk of death due to prostate cancer, there is no consensus at this time, among most prostate cancer experts, regarding the use of these hormone-blocking agents as prostate cancer prevention agents. However, for men with significant prostate cancer risk factors, it may be prudent to consider the use of Proscar or Avodart.
To learn more about the potential role of 5-alpha-reductase inhibitors in cancer risk reduction, look for the publication of my new landmark book, “A Cancer Prevention Guide for the Human Race,” in the spring/summer of this year.
Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author
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