ATLANTA—Shorter rather than longer courses of androgen suppression prior to radiation therapy are associated with fewer adverse effects in patients with intermediate-risk prostate cancer (PCa) but do not significantly affect oncologic outcomes, according to new findings presented at the American Society for Radiation Oncology’s 55th annual meeting.

The multi-institutional phase 3 trial evaluated 1,490 patients with intermediate-risk PCa from 152 institutions in the U.S. and Canada. Patients were accrued from 2000 to 2004. The patients had a mean age of 71 years at enrollment and a median follow-up of 8.7 years. Among the 1,490 patients, 94% had T1b-T2 disease, 73% had a Gleason score higher than 6, and 53% had PSA levels above 10 ng/mL.

Investigators randomized patients into two groups. Group 1 included 752 patients who received eight weeks of neoadjuvant total androgen suppression (TAS), which combined a luteinizing-hormone releasing-hormone analog plus a non-steroidal anti-androgen. Group 2 included 738 patients who received 28 weeks of neoadjuvant TAS. Both groups then received eight weeks of external beam radiation therapy (EBRT) and concurrent TAS.

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Thirty PCa-related deaths occurred in group 1, for a 10-year disease-specific survival (DSS) rate of 95%. Twenty-four PCa-related deaths occurred in group 2, for a 10-year DSS rate of 96%. The difference in DSS rates between the groups was not significant. An additional 200 and 196 non-PCa deaths occurred in group 1 and group 2, respectively. The 10-year overall survival rates for groups 1 and 2 were 66% and 67%, a non-significant difference between the groups.

By 10 years, 27% of patients had PSA failure (defined as nadir plus 2 ng/mL), 5% had PCa recurrence in the prostate, and 6% had distant metastasis. Hot flushes and erectile dysfunction were more common in group 2.

“Sometimes, preliminary research leads us to assume that more treatment is better, but this study serves as a strong cautionary note to put the promising treatment to the test,” said lead investigator Thomas M. Pisansky, MD, Professor of Radiation Oncology at Mayo Clinic in Rochester, Minn. “Overall, both groups had very, very good outcomes, but patients assigned to group 2 had more side effects from androgen suppression than group 1, who received only eight weeks of neoadjuvant total androgen suppression. Now, investigators know the upper boundary of how much androgen suppression is needed in this group of patients.”

These results have substantial importance because they can alter the research strategies in the future and may help simplify treatment and further reduce side effects, Dr. Pisansky said.

“In some ways the findings were quite surprising to me,” he said. “But I think the most important take-home message is that for men with intermediate risk prostate cancer all they need is 16 weeks of androgen suppression therapy.”