Data question ADT omission when using EBRT plus brachytherapy boost
medwireNews: Adding androgen deprivation therapy (ADT) to external beam radiotherapy (EBRT) may result in better survival than adding a brachytherapy boost in men with intermediate- and high-risk prostate cancer, network meta-analysis data suggest.
William Jackson (University of Michigan, Ann Arbor, USA) and co-investigators say that although current practice patterns show that “receipt of brachytherapy is independently associated with omission of ADT,” their study findings indicate that “ADT for these men should remain a critical component of treatment regardless of radiotherapy delivery method until randomized evidence demonstrates otherwise.”
The study included data from six randomized trials involving 4663 men who received EBRT with versus without ADT and three randomized trials involving 718 men who received EBRT with versus without brachytherapy. Two of the three brachytherapy trials allowed patients in both arms to also receive ADT. The majority (84%) of the men across all nine trials had intermediate- or high-risk prostate cancer.
A meta-analysis of the ADT trials showed that adding ADT to EBRT reduced the risk for death by a significant 29%. By contrast, there was no significant reduction in mortality risk when brachytherapy was added to EBRT.
The network meta-analysis, performed to theoretically compare EBRT plus ADT with EBRT plus brachytherapy, showed that receipt of EBRT plus ADT was associated with a significant 32% lower risk for death relative to EBRT plus brachytherapy.
Using this information, the researchers estimated that the 10-year cumulative incidence of overall mortality was 28% for EBRT plus ADT versus 41% for EBRT plus a brachytherapy boost.
They also used Bayesian modeling to show that there was an 88% probability that EBRT plus ADT would result in greater overall survival (OS) than EBRT plus brachytherapy.
Writing in the Journal of Clinical Oncology, the researchers comment that “[m]any have advocated that the use of brachytherapy can spare patients from ADT or shorten ADT duration, despite the lack of evidence for this approach.”
But they say their findings “question the validity of this practice and suggest that the use of EBRT plus ADT provides a high probability of superior OS in comparison with EBRT plus a brachytherapy boost without ADT.”
Jackson and co-authors note, however, that “recent evidence from ASCENDE-RT8 suggests that, compared with EBRT with ADT, the addition of a brachytherapy boost further improves biochemical and local control.”
They conclude that, based on their findings, “there is currently insufficient evidence to support the omission of ADT in men with intermediate- or high-risk prostate cancer treated with any form of definitive radiation therapy, including brachytherapy.”
They add: “[T]here is a great need for trials to be performed to understand the role of brachytherapy with the use of ADT in contemporary practice and with the potential integration of newer systemic treatment options.”
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