Five-year outcomes of fractionated stereotactic body radiotherapy for oligometastatic prostate cancer from the TRANSFORM phase II trial

Abstract

Metastasis-directed therapy (MDT) for oligometastatic prostate cancer (PCa), including stereotactic body radiotherapy (SBRT), has shown promise but is still considered investigational. This is the 5-year analysis of the TRANSFORM trial, the largest prospective cohort of men with oligometastatic PCa treated with SBRT-based MDT. The primary endpoint was 5-year treatment escalation-free survival (TE-FS), defined as freedom from any new cancer therapy other than further SBRT. In total, 199 men received SBRT; 76.4% were hormone-naïve at baseline. The rate of 5-year TE-FS was 21.7% (95% confidence interval [CI]: 15.7%–28.7%) overall and 25.4% (95% CI: 18.1%–33.9%) in the hormone-naïve subgroup. The subgroups with International Society of Urological Pathology Grade Groups 4–5 disease (hazard ratio [HR] = 1.48, 95% CI: 1.05–2.01, p =.026), a higher baseline prostate-specific antigen (PSA) (HR = 1.06, 95% CI: 1.03–1.09, p