Intermittent ADT fails to reduce toxicity in metastatic prostate cancer
CHICAGO — Intermittent androgen deprivation therapy increased ischemic and thrombotic events in a cohort of older men with metastatic prostate cancer compared with continuous therapy, according to study data presented at the ASCO Annual Meeting.
Further, intermittent ADT did not reduce the rate of long-term bone-related, cognitive or endocrine events compared with continuous ADT, results showed.
Dawn L. Hershman, MD, associate professor of medicine at Columbia University Medical Center, and colleagues evaluated data from the SWOG S9346 trial, which included 1,134 patients (mean age, 71.5 years) who received continuous or intermittent ADT.
“The objective was to evaluate the late effects by treatment arm to men randomized to intermittent vs. continuous ADT for metastatic prostate cancer,” Hershman said. “The hypothesis was that late effects would be lower in the intermittent arm.”
Researchers linked SWOG data to Medicare claims in order to evaluate late effects by treatment arm. Fifty-six percent of the trial participants had more than 1 year of continuous Medicare parts A and B coverage (intermittent ADT, n = 325; continuous ADT, n = 311).
Hypercholesterolemia (31%) and osteoporosis (21%) were the most common late effects recorded in the claims.
The 10-year cumulative incidence rate of ischemic and thrombotic events was 32% for patients receiving intermittent ADT and 23% for those receiving continuous ADT. These data equated to a 0.68 HR for the risk for these events with intermittent ADT (P = .02).
Patients who received continuous ADT demonstrated an increased risk for dementia; however, this association did not reach statistical significance.
Although researchers hypothesized intermittent ADT would reduce the rate for adverse events, patients in each arm demonstrated comparable rates for sexual dysfunction, cognitive dysfunction and bone-related or endocrine events.
“The curves were overlapping for the sexual dysfunction and endocrine events,” Hershman said.
She added that the findings of this study suggest that it is feasible to link clinical trials patients to insurance claims data. — by Rob Volansky
Hershman DL, et al. Abstract 5008. Presented at: ASCO Annual Meeting; May 29-June 2, 2015; Chicago.
Disclosure: Hershman reports no relevant financial disclosures. Please see the abstract for a complete list of the other researchers’ relevant financial disclosures.