Adverse Health Events Following Intermittent and Continuous Androgen Deprivation in Patients With Metastatic Prostate Cancer

IMPORTANCE Although intermittent androgen-deprivation therapy (ADT) has not been associated with better overall survival in prostate cancer (PC), it has the potential for lower adverse effects. To our knowledge, the incidence of long-term adverse health events has not been reported. OBJECTIVE To examine long-term late events in elderly patients randomized to intermittent or continuous ADT to determine whether late cardiovascular and endocrine events would be lower in patients treated with intermittent ADT. DESIGN, SETTING, AND PARTICIPANTS This was a secondary analysis of a multicenter clinical trial using linkage between patient data from S9346, a randomized SWOG trial of intermittent vs continuous ADT in men with metastatic PC, and corresponding Medicare claims. EXPOSURE Intermittent or continuous ADT. MAIN OUTCOMES AND MEASURES The main outcome was to identify long-term adverse health events by treatment arm. Patients were classified as having an adverse health event if they had any hospital claim-or at least 2 physician or outpatient claims at least 30 days apart-for any of the following diagnoses: ischemic and thrombotic events, endocrine events, sexual dysfunction, dementia, and depression. To incorporate time from beginning of observation through evidence of an event, we determined the cumulative incidence of each event. Competing risks Cox regression was used, adjusting for covariates. RESULTS In total, 1134 eligible US-based male patients with metastatic PC were randomized to continuous vs intermittent ADT in the S9346 trial. A total of 636 of trial participants (56%) had at least 1 year of continuous Medicare parts A and B coverage and no health maintenance organization participation. The median age was 71.3 years. The most common long-term events were hypercholesterolemia (31%) and osteoporosis (19%). The 10-year cumulative incidence of ischemic and thrombotic events differed by arm; 24% for continuous and 33% for intermittent ADT (hazard ratio, 0.69; P= .02). There were no statistically significant differences by arm in any other adverse health events. CONCLUSIONS AND RELEVANCE Contrary to our hypothesis that intermittent ADT would reduce long-term health-related events compared with continuous ADT, we found that older men assigned to intermittent ADT had no apparent reduction in bone, endocrine, or cognitive events and an increased incidence of ischemic and thrombotic events.