Intermittent ADT may benefit men with advanced prostate cancer

Beaver Creek, CO-Intermittent androgen suppression (IAS) is reported to be beneficial in select men with advanced prostate cancer, although definitive data are not yet available.

"These are attractive features to the patient who is facing the possibility of many years of androgen withdrawal."

The potential advantages of intermittent therapy are an improved quality of life, prolonged androgen dependence, which may delay recurrence and increase survival, and a significant cost savings. Although many physicians are already trying this approach, it remains the subject of many lingering questions: When to start and stop initial treatment, when to restart it, and what the long-term impact on survival and time to hormone resistance is when compared with continuous therapy.

Yet, for many patients, intermittent androgen suppression is still an attractive option.

"There are a lot of patients who ask for this type of treatment because they are tired of the side effects and cost associated with complete androgen suppression," said E. David Crawford, MD, professor of surgery and radiation oncology and head of the section of urologic oncology, University of Colorado Health Sciences Center, Denver. "While there are still a lot of unanswered questions about the best treatment protocol, there are no studies that show this type of treatment is detrimental to the patient."

Data are inconclusive

At the 16th annual International Prostate Cancer Update, Dr. Mendoza-Valdes presented a general overview of more than 20 completed studies of intermittent therapy. Overall, they have shown that intermittent androgen deprivation can result in disease control (erectile function recovery, as well as sexual desire and disappearance of other side effects of androgenic blockade) and outcomes that compare favorably with continuous androgen deprivation. Cost savings have been significant.

Other studies have suggested that continuous therapy may be over-treatment, and that shorter therapy sessions may allow some patients to be off therapy for several years. However, these studies have weaknesses, including small numbers of patients at varying stages of disease and lack of prospective randomized comparisons of intermittent with continuous therapy. Thus, the amount of time on therapy to achieve tumor regression and to improve survival is unknown.

Several ongoing large, multicenter, randomized phase III clinical trials are evaluating progression-free survival, overall survival, and quality of life for patients receiving intermittent therapy. Until these studies are completed and the data evaluated, this treatment protocol is considered experimental.

"We can't say it's a standard of treatment, but I think it is a good option for patients with advanced prostate cancer," said Dr. Mendoza-Valdes. "There is no scientific evidence that there are advantages regarding survival or time to hormone resistance, but there is no doubt that there are advantages in terms of quality of life."

Dr. Mendoza-Valdes reports that he has received grants or research support from AstraZeneca, and that he has received consulting fees from Lilly-ICOS.