ANAHEIM, May 21 -- Intermittent androgen deprivation for advanced prostate cancer led to a similar rate of progression to androgen-independent disease compared with continuous therapy and caused fewer hot flashes, found randomized trial.
The two-year rate of progression to androgen independence was 8.3% for patients given intermittent therapy and 6% in those treated with continuous therapy, a difference that was not statistically significant. The median time to progression was about two years in both groups.
"The rate of patients with androgen-independent progression was low, and intermittent therapy was as effective as continuous regarding progression-free survival," said Ulf Tunn, M.D., of the Akademische Stadtische Kliniken Offenbach in Frankfurt, Germany. "With the intermittent androgen therapy, the number of days with specific side effects was significantly lower. In particular, the number of days without hot flashes was twice that of continuous therapy in the intermittent arm."
The findings came from a study involving 244 patients who had biochemical relapse (PSA ≥1 ng/mL) following a radical prostatectomy. All patients received 11.25 mg of leuprolineacetate, and those whose PSA levels decreased to <0.5 ng/ml after six months were randomized to intermittent or continuous therapy. Patients in the intermittent group were retreated whenever PSA values increased to ≥3 ng/ml.
Subsequently, 167 patients qualified for randomization. The primary endpoint of the study was the proportion of patients who had clinical or biochemical progression during treatment. The secondary endpoint was the incidence of adverse events.
In the intermittent group, the time off treatment averaged about one year during the first cycle of treatment and approximately six months during the second cycle. Retreatment continued for a minimum of six months.
Testosterone levels reached normal levels (>2.3 ng/ml) in 92.7% of intermittent patients during the first treatment cycle and in 81.1% in the second cycle. Serum testosterone returned to baseline levels in 79.3% of the intermittent group during the first cycle and 64.9% during the second cycle.
Overall, 12 of 167 patients (7.2%) had androgen-independent progression after 2 years. Progression occurred in seven of 84 patients in the intermittent group and five of 83 in the continuous group.
Intermittent therapy was associated with a significant reduction in the number of days with hot flashes per quarter, an average of 23 versus 46 in the continuous group (P<0.001). Health-related quality of life remained essentially unchanged in the intermittent group (mean score of 71.0 at baseline and 71.3 after two years), whereas the average quality of life score declined in the continuous group (70.8 at baseline and 68.4 at 2 years).
Dr. Tunn did not present data on changes in bone mineral density (BMD). In response to a question from the audience, he said BMD was better preserved in the intermittent group than in the continuous group.
Martin Gleave, M.D., the University of British Columbia in Vancouver, who co-chaired the session at which Dr. Tunn presented the findings, questioned whether the small number of patients in the study provided an adequate test of intermittent therapy's effect on disease progression compared to CAD.
"A similar trial for the North American cooperative study groups is evaluating PSA recurrence after radiation therapy," said Dr. Gleave. "We have a sample size of 1,300 because the number of events might be very low and difficult to pick up over time. What is your feeling about being able to detect a difference over time in your set, given the sample size?"
"What I am feeling now is that there will be no difference between continuous or intermittent therapy, but patients will benefit from intermittent therapy by a reduction in adverse events," Dr. Tunn responded.
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