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Intermittent ADT fails to reduce long-term events in metastatic prostate cancer
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Intermittent androgen deprivation therapy did not reduce the long-term occurrence of bone, endocrine or cognitive adverse events compared with continuous androgen deprivation therapy among older men with metastatic prostate cancer, according to a secondary analysis of SWOG 9346.
Further, intermittent ADT increased the incidence of ischemic and thrombotic adverse events, results showed.
Dawn L. Hershman
Intermittent ADT has been associated with fewer adverse events, but not increased OS, among men with prostate cancer, according to study background. However, the incidence of long-term adverse events have not been studied.
Thus, Dawn L. Hershman, MD, MS, associate professor of medicine at Columbia University Medical Center, and colleagues sought to observe long-term late events among older patients randomly assigned to intermittent vs. continuous ADT. Researchers conducted a secondary analysis of the SWOG 9346 trial — which evaluated the efficacy of intermittent vs. continuous ADT in men with metastatic prostate cancer — and evaluated corresponding Medicare claims.
The identification of long-term adverse health events by treatment arm served as the primary endpoint. The researchers classified adverse health events as any hospital claim — or at least two physician or outpatient claims at least 30 days apart — resulting in any of the following diagnoses: ischemic and thrombotic events, endocrine events, sexual dysfunction, dementia and depression.
The study included data from 636 trial participants (median age, 71.3 years) who had at least 1 year of continuous Medicare parts A and B coverage and no HMO participation, representing 56% of total U.S. patients enrolled in the trial.
The most commonly identified long-term events included hypercholesterolemia (31%) and osteoporosis (19%).
The 10-year cumulative incidence of all ischemic and thrombotic events was higher in the intermittent ADT arm (33% vs. 24%; HR = 0.69; P = .02).
However, patients in the continuous and intermittent ADT arms experienced comparable 10-year cumulative rates of bone events (31% vs. 26%), endocrine events (44% vs. 41%), sexual dysfunction (6% vs. 5%), dementia (7% vs. 3%) and depression (14% vs. 14%).
The researchers noted limitations of their study, including the possibility that patients experienced adverse events not reported to Medicare. Further, they noted that complications might have been underestimated in older men, due to the potential underreporting of minor adverse events.
Ian F. Tannock
“If these findings are confirmed, given the failure of the parent study to prove its noninferiority endpoint, clinicians should be cautious about using intermittent ADT therapy in older men with metastatic prostate cancer, given our inability to demonstrate a reduction in long-term adverse health events, the primary rationale for intermittent ADT,” Hershman and colleagues wrote.
The risks associated with intermittent ADT might outweigh the benefits for many patients, Saroj Niraula, MBBS, MD, medical oncologist at CancerCare Manitoba and assistant professor of medicine at University of Manitoba in Winnipeg, and Ian F. Tannock, MD, PhD, professor emeritus of medicine and medical biophysics at University of Toronto, wrote in an accompanying editorial.
“For men with symptomatic metastatic prostate cancer, ADT remains the important cornerstone of treatment, and the study by Hershman and colleagues supports the conclusion of lack of beneficial effects of intermittent compared with continuous ADT in men with prostate cancer,” Niraula and Tannock wrote. “In the absence of a survival advantage in favor of either strategy, any advantage of intermittent ADT is likely to be limited to possible improvements in quality of life, particularly during the off-treatment period; convenience of therapy; and savings in cost.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures. Niraula and Tannock report no relevant financial disclosures.
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