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Duration of Androgen Suppression and Zoledronic Acid in Locally Advanced Prostate Cancer

By: Hillary Ojeda
Posted: Tuesday, January 22, 2019

A duration of 18 months of androgen suppression plus radiotherapy seems to be associated with better disease-specific survival than 6 months of androgen suppression plus radiotherapy in patients with locally advanced prostate cancer, according to the 10-year results of the phase III TROG 03/04 RADAR trial. James W. Denham, MD, FRANZC, of the University of Newcastle, Australia, and colleagues also found that adding zoledronic acid offered no additional benefit to either regimen. Their findings were published in The Lancet Oncology.

The trial randomly assigned 1,071 men with locally advanced prostate cancer between October 2003 and August 2007 evenly to 4 treatment groups: 6 months of neoadjuvant androgen suppression with leuprorelin and radiotherapy (short-term group); 6 months of neoadjuvant and 12 months of adjuvant androgen suppression with leuprorelin and radiotherapy (intermediate-term group); short-term therapy plus 18 months of zoledronic acid; intermediate-term therapy plus 18 months of zoledronic acid. Radiotherapy to the prostate and seminal vesicles beginning at the end of the fifth month of androgen suppression was given to all study patients.

The median follow-up was 10.4 years. No significant interactions between androgen suppression and zoledronic acid were found, so the investigators combined the groups and analyzed them by the duration of androgen suppression. The adjusted cumulative incidence of prostate cancer–specific mortality was higher with short-term than intermediate-term therapy (13.3% vs. 9.7%), with an absolute difference of 3.7%. Moreover, prostate cancer–specific mortality did not seem to be affected by the addition of zoledronic acid, with a cumulative incidence of 11.2% with and 11.7% without zoledronic acid (absolute difference of –0.5%).

“Evidence from the [RADAR] and French Canadian Prostate Cancer Study IV trials suggests that 18 months of androgen suppression with moderate radiation dose escalation is an effective but more tolerable option than longer durations of androgen suppression for men with locally advanced prostate cancer, including intermediate- and high-risk elements,” they concluded.

Disclosure: The study authors’ disclosure information may be found at thelancet.com.



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