Optimal Period of ADT May Vary Depending on Receipt of Brachytherapy in High-Risk Prostate Cancer

The optimal minimum duration of androgen deprivation therapy (ADT) may be less than 18 months for high-risk prostate cancer patients receiving external beam radiation therapy plus brachytherapy (EBRT + BT), but more than 18 months for patients receiving EBRT alone, according to a study of 3 cohorts in which distant metastasis-free survival (DMFS) was the primary end point, while overall survival (OS) was the secondary end point.

“Given the adverse effects of ADT, it is commonly under-used in real-world settings, with men receiving considerably shorter durations of ADT than indicated,” stated lead author Amar Kishan, MD, department of radiation oncology, UCLA, alongside coinvestigators.

The 3 cohorts studied were DART and RADAR (both of which were phase 3 randomized control trials), and a retrospective cohort assembled from databases.

In Deprivación Androgénica y Radio Terapía (DART), 91 patients were treated with EBRT at 10 treatment centers in Spain from 2005 to 2010. In Randomized Androgen Deprivation and Radiotherapy (RADAR), 181 participants were treated with EBRT and 203 with EBRT+ BT at 23 treatment centers in Australia and New Zealand between 2003 and 2007. The retrospective cohort was assembled by querying databases from 16 tertiary referral centers and consisted of 1827 patients treated with EBRT and 1108 patients treated with EBRT+ BT from 2000 to 2014.

The entire study population totaled 2935 patients. For those patients who received EBRT without BT, receiving ADT for 18 months or more was associated with improved outcomes compared with receiving ADT for less than 6 months (DMFS HR, 0.44; 95% CI, 0.31-0.63; P <.001; OS HR, 0.45; 95% CI, 0.30-0.68; P <.001).

In DART, 28 months of ADT for patients who received EBRT alone was associated with improved DMFS compared with 18 months. But in RADAR, on the other hand, the prolongation of ADT for patients receiving EBRT only was not associated with significant improvements in DMFS (HR, 1.01; 95% CI, 0.65-1.57); but in EBRT + BT patients, it was (DMFS HR, 0.56; 95% CI, 0.36-0.87; P = .01).

Source:
Kishan A, Steigler A, Denham J, et al. Interplay Between Duration of Androgen Deprivation Therapy and External Beam Radiotherapy With or Without a Brachytherapy Boost for Optimal Treatment of High-risk Prostate Cancer A Patient-Level Data Analysis of 3 Cohorts, JAMA Oncol. Published online January 20, 2022. doi:10.1001/jamaoncol.2021.6871