Bipolar androgen therapy sensitizes castration-resistant prostate cancer to subsequent androgen receptor ablative therapy

Background: Cyclical, high-dose testosterone administration, termed bipolar androgen therapy (BAT), can induce clinical responses and restore sensitivity to androgen signalling inhibition in patients with previously treated castration-resistant prostate cancer (PCa) (CRPC). This trial evaluated whether BAT is a safe and effective first-line hormonal therapy for patients with CRPC. Patients and Methods: In cohort C of this single-centre, open-label, phase II, multi-cohort trial (RE-sensitizing with Supraphysiologic Testosterone to Overcome REsistance study), 29 patients with CRPC received first-line hormonal therapy with 400 mg of testosterone cypionate intramuscularly every 28 days concurrent with a luteinising hormone-releasing hormone agonist/antagonist. The primary end-point of the study was the PSA₅₀ response rate to BAT treatment. Results: After treatment with BAT, four of 29 patients (14%; 95% confidence interval [CI]: 4–32%) experienced a PSA₅₀ response. The median radiographic progression-free survival to BAT was 8.5 months (95% CI: 6.9–15.1) for patients with metastatic CRPC. After progression on BAT, 17 of 18 patients (94%; 95% CI: 73–100%) achieved a PSA₅₀ response and 15 of 18 patients (83%; 95% CI: 59–96) achieved a PSA₉₀ response on abiraterone or enzalutamide. Twelve of 15 patients (80%; 95% CI: 52–96) with metastatic CRPC remain on abiraterone or enzalutamide with a median duration of follow-up of 11.2 months. Conclusion: As first-line hormonal treatment for CRPC, BAT was well tolerated and resulted in prolonged disease stabilisation. After progression on BAT, patients had favourable responses to second-generation androgen receptor–targeted therapy. Trial Registration: ClinicalTrials.gov