Many men with metastatic prostate cancer live longer on continuous hormone therapy

Many men with metastatic, hormone-sensitive prostate cancer live longer on continuous androgen-deprivation therapy (also known as hormone therapy) than on intermittent therapy, according to a seventeen-year study led by SWOG, a cancer research cooperative group funded by the National Cancer Institute (NCI).

Men with newly diagnosed metastatic prostate cancer are usually either surgically castrated or given medications to suppress the production of male hormones that drive their cancer. The treatment can help keep the disease at bay temporarily, but in the majority of patients the cancer will relapse and contribute to the patient's death.

Surgical castration is permanent but "medical castration" provides men the potential advantage of receiving therapy intermittently. A halt in this therapy is followed in time by a rise in testosterone levels. Scientific data suggested that intermittent treatment may delay the cancer relapse, and that the rise in testosterone may result in an improvement in the patient's quality of life.

These data provided the rationale for the phase III clinical trial SWOG-9346, the largest such study to date in men with metastatic, hormone-sensitive disease. Results of this study demonstrate that intermittent androgen-deprivation (AD) therapy is not as good as continuous hormone therapy with regard to patient longevity.

The findings are to be presented today at the plenary session of the American Society for Clinical Oncology's (ASCO's) annual meeting by the study's principal investigator, Maha Hussain, M.D., F.A.C.P., of the University of Michigan Comprehensive Cancer Center.

"Based on these results," Hussain says, "we can conclude that intermittent AD is not as effective as continuous AD in men with metastatic prostate cancer."

Clinical researchers from the SWOG network, with funding from the NCI, led an international team in conducting the study at more than 500 sites, enrolling 3,040 men with hormone-sensitive, metastatic prostate cancer between 1995 and 2008.

All men got an initial course of androgen-deprivation treatment for seven months. The 1,535 eligible men whose prostate-specific antigen (PSA) level dropped to 4 ng/mL or less by the end of those seven months were then assigned at random to stop therapy (the intermittent therapy group) or continue therapy (the continuous therapy group).

Those randomized to the intermittent therapy arm had their treatment suspended until their PSA rose to a predetermined level, at which time they started another seven-month course of androgen-deprivation therapy, cycling on and off therapy in this way as long as their PSA levels continued to respond appropriately during the "on" cycle.

Men on continuous therapy had a median overall survival time of 5.8 years from the time of randomization, with 29 percent of these men surviving at least 10 years. Those on intermittent therapy had a median overall survival time of 5.1 years, with 23 percent surviving at least 10 years from the time they were randomly assigned to a treatment arm.

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