Wednesday, February 23, 2022 CCTG PR22: DASL-HiCaP: Darolutamide augments standard therapy for localized very high-risk cancer of the prostate (ANZUP1801). a randomized phase 3 double-blind, placebo-controlled trial of adding darolutamide to androgen deprivation therapy and definitive or salvage radiation. This is an international trial with sites accruing in Australia, New Zealand, US, UK, Ireland and Canada. Background: Radiation therapy (RT), plus androgen deprivation therapy (ADT) with a luteinizing hormone releasing hormone analog (LHRHA), is standard of care for men with very high-risk localized prostate cancer (PC), or with very high-risk features and persistent PSA after radical prostatectomy (RP). Despite this, incurable distant metastases develop within 5 years in 15% of men with very high-risk features. Darolutamide is a structurally distinct oral androgen receptor antagonist with low blood-brain-barrier penetration, a demonstrated favorable safety profile, and low potential for drug-drug interactions. Our aim is to determine the efficacy of adding darolutamide to ADT and RT in the setting of either primary definitive therapy, or salvage therapy for very high-risk PC. Methods: This study is a randomized (1:1), phase 3, placebo-controlled, double-blind international trial for men planned for RT who have very high-risk localized PC on conventional imaging; or very high-risk features with PSA persistence or rise within one year following RP. The trial is stratified by: RP; use of adjuvant docetaxel; pelvic nodal involvement. 1100 participants will be randomized to darolutamide 600 mg or placebo twice daily for 96 weeks in combination with SOC: LHRHA for 96 weeks, plus RT starting week 8-24 from randomization. Participants are allowed nonsteroidal antiandrogen in addition to LHRHA for up to 90 days prior to randomization. Early treatment with up to 6 cycles of docetaxel completed at least 4 weeks prior to RT is permitted. The primary endpoint is metastasis-free survival (ICECaP-validated), with secondary endpoints overall survival, PC-specific survival, PSA-progression free survival, time to subsequent hormonal therapy, time to castration-resistance, frequency and severity of adverse events, health related quality of life, fear of recurrence. Tertiary endpoints include incremental cost-effectiveness, and identification of prognostic and/or predictive biomarkers of treatment response, safety, and resistance to study treatment. Clinical trial information: NCT04136353.