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Biochemical failure rate unaffected by addition of androgen suppression therapy to combined brachytherapy, EBRT in men with intermediate-risk disease, research indicates

Tuesday, January 26 2010 | Comments

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What's This? In men with intermediate-risk prostate cancer, androgen suppression therapy administered as an adjuvant to combined brachytherapy and external beam irradiation (EBRT) fails to improve biochemical failure, according to study results.

Although the positive interaction between androgen suppression therapy and EBRT for intermediate- and high-risk prostate cancer has been demonstrated in previous studies, the optimal duration of hormonal therapy is less clear, and the external beam dose given in prior investigations is now considered to be low, the investigators explained. They noted that the relative benefits of radiation dose versus hormonal therapy are not established.

To examine the relationship between radiation dose and androgen suppression therapy, the investigators conducted a retrospective analysis of 432 men with intermediate-risk prostate cancer who were treated with low dose rate brachytherapy and EBRT with (n=350) or without (n=82) androgen suppression therapy, which was initiated 3 months before seed implantation and lasted a median of 9 months. Seventy-six percent of the cases had a Gleason score of 7, and the median prostate-specific antigen (PSA) level was 7.6 ng/mL (range, 1.4 ng/mL-20 ng/mL).

The biologically effective dose (BED) was calculated based on the combination of brachytherapy and EBRT total dose and ranged from 142 Gy2 to 280 Gy2 (median, 206 Gy2).

The main outcome measure was 8-year biochemical failure-free rate, and the results showed that the rate was 92%, regardless of receipt of androgen suppression therapy (P=.4).

Androgen suppression therapy had no effect on this rate relative to no hormonal therapy in the subgroup of men with a Gleason score of 7 (92% vs 90.5%; P=.55), PSA 10 ng/mL to 20 ng/mL (92% vs 100%; P=.32), clinical stage T2b-T2c disease (89.5% vs 97%; P=.27), or >1 intermediate risk feature (90% vs 100%; P=.2).

Additionally, hormonal therapy had no effect when the patients were analyzed according to high or low BED groups. In the subset of patients with BED <206 Gy2, the 172 men who received androgen suppression therapy had an 8-year biochemical failure-free rate of 97%, whereas the rate for the 31 men who received no hormonal therapy was 86% (P=.98). In the subset of patients with BED >=206 Gy2, the 174 men who received hormonal therapy had an 8-year biochemical failure-free rate of 89% and the 50 men who did not receive hormonal therapy had a rate of 94% (P=.30).

"Androgen suppression therapy given as adjuvant therapy with combined implantation and EBRT in patients at intermediate risk failed to improve biochemical control," the authors concluded. "Although individualized treatment plans may still include androgen suppression therapy, it should not be used routinely without considering its potential associated morbidity." (Stock RG, et al. J Urol 2010;183:546-551.)

In an accompanying editorial, Mack Roach said the data in this study are not compelling enough to recommend abandoning androgen suppression therapy in all intermediate-risk cases. "Intermediate-risk disease includes a heterogeneous group of cases with some at low and some at high risk," Roach said. He noted that the cases in the study were "relatively favorable." (J Urol 2010;183:551.)

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