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

Abstract

AbstractMetastasis‐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 < .001) and those who received prior androgen deprivation therapy (ADT) (HR = 2.13, 95% CI: 1.40–3.26, p < .001), were at greater risk of treatment escalation. Outcomes for participants with four or five initial lesions were comparable to those with one to three lesions. At last follow‐up, 18.9% (95% CI: 13.2%–25.7%) of participants were free from treatment escalation (median follow‐up of 67.9 months) and two participants had an undetectable PSA level. No treatment‐related grade three or higher adverse events were reported. The findings of this study demonstrate that SBRT‐based MDT is an effective option for delaying systemic treatment escalation in the context of oligometastatic PCa. Future randomised trials comparing SBRT‐based MDT to standard‐of‐care ADT‐based approaches are required to evaluate the impact of delaying ADT on survival.