5602 Background: LHRH agonists are the mainstay for medical castration in advanced prostate cancer; however, they cause an initial testosterone (T) surge with a delayed onset of castration and require depot injection. Relugolix is the first oral GnRH receptor antagonist, which was previously shown to rapidly suppress T levels. The HERO trial compared the safety and efficacy of relugolix with leuprolide acetate in advanced prostate cancer patients. Methods: HERO is a 48-week, global, pivotal phase III trial that randomized 934 patients with androgen-sensitive advanced prostate cancer in a 2:1 ratio to receive relugolix 120 mg orally QD after a single l or leuprolide acetate 3-month depot injection. The primary endpoint was to achieve and maintain serum T suppression to castrate levels (< 50 ng/dL) through 48 weeks. Key secondary endpoints included castration rates at Day 4, profound castration (< 20 ng/dL) rates at Days 4 and 15, PSA response rate at Day 15 and FSH levels at Week 25. Testosterone recovery was evaluated in a subset of 184 patients. Results: A total of 96.7% (95% CI: 94.9%, 97.9%) of men on relugolix achieved and maintained castration through 48 weeks compared to 88.8% on leuprolide. The difference of 7.9% (95% CI: 4.1%, 11.8%) demonstrated non-inferiority (margin -10%) and superiority (P < 0.0001) of relugolix to leuprolide. All key secondary efficacy endpoints tested demonstrated superiority over leuprolide (P < 0.0001) (Table). In the testosterone recovery subset, median T levels were 270.76 ng/dL in the relugolix compared to 12.26 ng/dL in the leuprolide group 90 days after discontinuation of therapy. In a prespecified analysis, the incidence of major adverse cardiovascular events (MACE) was lower in the relugolix group than in the leuprolide group (2.9% vs. 6.2%, respectively); otherwise the safety and tolerability profiles were generally similar. Conclusion: Relugolix achieved castration as early as Day 4 and demonstrated superiority over leuprolide in sustained T suppression through 48 weeks, faster T recovery after discontinuation and a 50% reduction in MACE. Relugolix has the potential to become a new standard for T suppression for patients with advanced prostate cancer. Clinical trial information: NCT03085095 . [Table: see text]
RTOG 0518: randomized phase III trial to evaluate zoledronic acid for prevention of osteoporosis and associated fractures in prostate cancer patients
