RADIOSA Trial Shows ADT Addition to SBRT Improves Progression-Free Survival in Oligorecurrent Prostate Cancer
Key Insights
The RADIOSA phase II trial demonstrated that adding 6 months of androgen-deprivation therapy (search) to stereotactic body radiotherapy (search) significantly improved median progression-free survival from 15.1 to 32.2 months in hormone-sensitive oligorecurrent prostate cancer (search) patients.
The combination therapy showed a 57% reduction in disease progression risk with minimal toxicity, representing the first randomized trial to show clinical benefit of SBRT (search) plus short-course ADT in this patient population.
Results reinforce the role of metastasis-directed therapy in delaying systemic treatment escalation, though researchers emphasize the need for biomarkers to identify patients who might benefit from SBRT (search) alone.
The addition of androgen-deprivation therapy (search) (ADT) to stereotactic body radiotherapy (search) (SBRT (search)) significantly improved progression-free survival in patients with hormone-sensitive oligorecurrent prostate cancer (search), according to results from the RADIOSA phase II trial published in The Lancet Oncology. The Italian single-center study represents the first randomized trial to demonstrate clinical benefit of combining SBRT with short-course ADT in this patient population.
Trial Design and Patient Population
The open-label RADIOSA trial enrolled 102 efficacy-evaluable patients at the European Institute of Oncology (search), IRCCS, Milan, between August 2019 and April 2023. Patients were randomly assigned to receive either SBRT (search) plus ADT (n=51) or SBRT alone (n=51). The SBRT regimen consisted of 30 Gy delivered in three fractions every other day, equivalent to 98.6 Gy in 2-Gy fractions. ADT treatment involved 6 months of luteinizing hormone-releasing hormone analog (search) therapy initiated within one week before SBRT.
Significant Improvement in Disease Control
After a median follow-up of 31 months, the combination therapy demonstrated substantial clinical benefits. Median progression-free survival reached 32.2 months in the SBRT (search) plus ADT group compared to 15.1 months with SBRT alone, representing a 57% reduction in progression risk (hazard ratio = 0.43, 95% CI = 0.26-0.72, P = 0.0010).
The progression-free survival rates at key time points highlighted the sustained benefit of combination therapy. At one year, 96% of patients in the combination group remained progression-free versus 63% in the SBRT (search)-only group. At two years, these rates were 61% versus 33%, respectively.
Biochemical Response and Safety Profile
Biochemical progression-free survival also favored the combination approach, with median times of 26.8 months versus 12.6 months for SBRT (search) plus ADT and SBRT alone, respectively (HR = 0.40, P = 0.0002). Overall survival remained excellent across both groups, reaching 100% at one year and 95% at two years among all patients.
The safety profile proved favorable with minimal severe toxicity. Only one grade 3 treatment-related adverse event occurred—left ureter stenosis in a patient receiving combination therapy. No grade 4 or 5 treatment-related events or late toxicities were observed. ADT-related side effects were predominantly grade 1 or 2, including hot flushes (43%), asthenia (16%), insomnia (8%), and muscular pain (4%).
Clinical Implications and Future Directions
The investigators emphasized the significance of these findings for metastasis-directed therapy approaches. "By demonstrating improved clinical progression-free survival, the RADIOSA trial reinforces the role of metastasis-directed therapy in delaying systemic treatment escalation," the researchers noted. However, they acknowledged that "carefully selected patients might still benefit from SBRT (search) alone."
The study authors highlighted important areas for future research, including determining the optimal duration of ADT and identifying biomarkers that could predict response to SBRT (search) monotherapy. These developments could help personalize treatment approaches and avoid unnecessary ADT exposure in patients who might achieve similar outcomes with radiation alone.
The RADIOSA trial provides compelling evidence for combination therapy in hormone-sensitive oligorecurrent prostate cancer (search), offering a new standard of care option that significantly extends time to disease progression while maintaining an acceptable safety profile.