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Report: On-and-Off Approach to Prostate Cancer Treatment May Compromise Survival

Intermittent androgen deprivation not equivalent to continuous therapy (Apr. 4)

Taking a break from hormone-blocking prostate cancer treatments once the cancer seems to be stabilized is not equivalent to continuing therapy, according to a report from the University of Michigan Comprehensive Cancer Center.

Based on previous smaller studies, it looked like an approach called intermittent androgen deprivation therapy might be just as good as continuous androgen deprivation in terms of survival while giving patients a reprieve from the adverse effects of therapy. In fact, researchers believed that intermittent therapy might help overcome treatment resistance, which occurs in most patients with metastatic hormone-sensitive prostate cancer.

However, a new international study, which treated 1,535 patients with metastatic prostate cancer and followed them for a median period of 10 years, has found that’s not the case. The findings were published in the New England Journal of Medicine.

“We tried to see whether intermittent androgen deprivation is as good as continuous androgen deprivation, but we did not prove that. We found that intermittent therapy is certainly not better, and, moreover, we cannot even call it comparable,” said lead author Maha Hussain, MD, FACP.

In the study, men with metastatic hormone-sensitive prostate cancer were given an initial course of androgen deprivation therapy (hormone therapy), which is standard treatment for the disease. Patients with a stable or declining prostate-specific antigen (PSA) level equal to or below a cut-off of 4 ng/mL were then randomly assigned to continue or discontinue the hormone therapy. The patients were carefully monitored with monthly PSA tests and with a physician’s evaluation every 3 months. Therapy was resumed in the intermittent-treatment arm when PSA levels increased to 20 ng/mL. The intermittent cycle continued on and off, based on PSA levels.

Survival in the two treatment groups showed a 10% relative increase in the risk of death with intermittent therapy, with an average survival period of 5.8 years for the continuous-treatment group versus 5.1 years for the intermittent-treatment group from the time of randomization.

The researchers also looked at quality of life between the two groups. Initially, the intermittent-therapy group showed significant improvement in impotence and emotional function in the first 3 months and had improved trends in other aspects of quality of life compared with the continuous-therapy group. However, these differences leveled off over time.

“If a patient comes in with newly metastatic prostate cancer, continuous hormone treatment is the standard. If they wish to do intermittent treatment, they should be counseled that, based on these data, their outcome might be compromised,” Hussain said.

Sources: UM Comprehensive Cancer Center; April 4, 2013; and NEJM; April 4, 2013.

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