Intermittent androgen deprivation therapy appears viable for advanced prostate cancer

Lisbon, Portugal-Men with advanced prostate cancer had similar survival with intermittent or continuous androgen deprivation therapy (ADT), pooled data from two randomized trials showed.

After adjustment for differences between the two studies, overall survival was almost identical (hazard ratio: 0.99) in men treated with intermittent or continuous ADT, according to the data, which were presented at the AUA annual meeting in San Diego.

Men younger than 75 years of age and with a favorable risk profile fared significantly worse with continuous ADT (p=.031). The data also showed that men 65-79 years of age with favorable prognostic features would likely remain off therapy for prolonged periods. In that subgroup, intermittent therapy proved to be noninferior to continuous therapy (HR: 1.16, p=.38).

Intermittent ADT was also associated with less cardiovascular risk and sexual dysfunction.

“Intermittent therapy should be considered for use in routine practice since it is associated with no reduction in survival. It may be particularly beneficial for patients who are good responders to initial therapy,” said first author Fernando Calais da Silva II, MD, director of the urology service at Centro Hospitalar de Lisboa Central in Lisbon, Portugal.

Relatively few trials have compared continuous and intermittent ADT for advanced prostate cancer. Pooling data from published studies offers a means to examine the relative safety and efficacy of the two strategies.

Dr. da Silva reported findings from an analysis of two trials involving 1,544 patients who were randomized to continuous or intermittent ADT following induction therapy. The trials had similar protocols, data collection, and follow-up management.

In both trials, patients received 3 months of induction therapy with cyproterone (Cyprostat) and monthly depot injections of a luteinizing hormone-releasing hormone analog. In both trials, patients who achieved a PSA level <4.0 ng/mL were eligible for randomization to continued treatment with the same regimen or to intermittent therapy. In one trial, intermittent ADT was the same as induction, and in the other, patients received only cyproterone.

No difference in survival observed

The pooled data showed no difference in survival between continuous and intermittent ADT (p=.90).

Subgroup analysis showed that patients who had no metastases, Gleason score <7, were age <75 years, and who achieved a PSA level <1.0 ng/mL at randomization had a good prognosis. In that low-risk group, continuous therapy led to worse survival as compared with intermittent ADT (HR: 1.60). Investigators found no difference in treatment effect between the two studies. In a model that incorporated the same variables but changed age to 65-79 years, intermittent ADT was not inferior to continuous therapy.

Other analyses showed that patients with M1 status had similar survival with both ADT strategies, as did patients with normal bone scans, one to six hot spots, or more than six hot spots.

“Among patients with low PSA at randomization (<1.0 ng/mL), intermittent therapy is better than continuous,” Dr. da Silva said. “Among the 1,544 randomized in both studies, 741 (48%) had a PSA less than 1 after 3 months of induction therapy.”

During follow-up of the low-risk subgroup, 25 patients on continuous ADT died of cardiovascular causes as compared with 10 randomized to intermittent therapy.UT

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