Table of Contents

Chapter 6: Using Hormone Therapy

i. Intermittent Therapy

Although the LHRH agonists (with or without the addition of an antiandrogen) are very effective at keeping the cancer at bay for periods of time, the resultant loss of testosterone can have significant side effects in many men. Over the years, researchers have explored different ways to minimize these side effects. The most commonly explored strategy is known as intermittent therapy.

This strategy takes advantage of the fact that it takes a while for testosterone to begin circulating again after LHRH agonists are removed. The LHRH agonist is used for six to twelve months, during which time a low PSA level is maintained. The drug is stopped until the PSA rises to a predetermined level, at which point the drug is restarted. The "drug holidays" in between cycles allow men to return to nearly normal levels of testosterone. Sexual function and other important quality of life measures might return before the next cycle begins again.

From a treatment perspective, there might be a benefit as well to intermittent therapy. As we discussed earlier, hormone therapy is a temporary solution, as the hormone-independent cells eventually become strong enough that hormone therapies will have less and less of an effect on the growth of the tumor. Laboratory studies have shown that the intermittent approach exploits this feature, and allows the cells that are sensitive to hormone therapies to grow during each "off" cycle, potentially extending the hormonal sensitivity of the tumors.

At this time, the true benefits of this approach remain unclear, and large clinical trials are currently underway to evaluate its use in men with advanced prostate cancer. If the approach proves to be as effective as continuous therapy in suppressing tumor growth, intermittent therapy will likely become popular because of potential for an improved side effect profile.