The long view.

Top Line: The debate continues on how long to sign-up men for androgen deprivation therapy when receiving definitive radiation for high-risk prostate cancer.

The Study: Here is a combined look at 3 studies, both retrospective and prospective, including 3410 men receiving either external beam radiation alone (EBRT, n=2099) or EBRT + brachytherapy (n=1311) along with an array of durations of ADT. As hypothesized, there was a significant interaction between the treatment type (EBRT versus EBRT+BT) and the benefit of longer ADT duration. Complicated analytical methods on the large multi-institutional retrospective database concluded the minimum duration for ADT was 26 months with EBRT versus only 12 months with EBRT+BT in order to optimize distant metastasis-free survival. This was then validated by analyzing individual patient data on those receiving definitive radiation for high-risk disease on the two available prospective trials evaluating prolongation of ADT (RADAR and DART). The authors best explain this validation of sorts: “If the optimal duration of ADT with high-dose EBRT were to truly be 26 months (>18 months), then the effect observed in the RADAR trial (comparing 18 with 6 months) would be small, whereas the effect observed by comparing the 28-month arm of the DART with either the 6- or 18-month arm of RADAR would be significant—this was seen. On the other hand, if the optimal duration of ADT with EBRT+BT were to truly be 12 months, then the effect observed in the RADAR trial would be large, as was the case.”

TBL: This study provides more support that prolonging ADT >18 months confers a benefit when coupled with external beam radiation alone, but not with EBRT + brachytherapy, for high-risk prostate cancer. | Kishan, JAMA Oncol 2022