Stereotactic body radiotherapy for oligorecurrent granulosa cell tumours

Objective: To evaluate the efficacy and safety of stereotactic body radiotherapy (SBRT) in patients with oligorecurrent granulosa cell tumours (GCTs). Methods: We retrospectively analysed 26 patients treated with ablative SBRT for oligorecurrent GCT at the European Institute of Oncology between May 2007 and November 2023. Primary endpoints were the time to next systemic therapy (TNST) and local control (LC). Secondary outcomes were progression-free survival (PFS), overall survival (OS), and SBRT-related acute adverse events. Kaplan-Meier analyses were used for time-to event outcomes, and Cox regression was performed only for enpoint with observed events. Inhibin B levels before and after SBRT were compared using the Wilcoxon signed-rank test. Results: Seventy-two lesions were treated, most commonly at visceral (41.7%) and lymph node (20.8%) sites. Median follow-up was 4.1 years. Median TNST was 6.26 years, with 2-, 3-, and 5-year rates of 80.8%, 60.6% and 50.5%, respectively. Five-year LC was 90.7%. The 2-,3-, and 5-yeat PFS rates were 28.4%,14.2% and 7.1%, respectively. No deaths occurred during follow-up and median OS was not reached. Inhibin B levels declined significantly after SBRT (median 107.1 to 30.0 ng/L; p < 0.001). SBRT was well tolerated with no acute adverse events in 50% of patients and only grade 1 events in 42.3%, mainly gastrointestinal. Conclusions: SBRT should be considered an effective and safe metastasis-directed treatment for selected patients with oligorecurrent GCT, providing durable LC and delaying further systemic therapy. These findings support the incorporation of SBRT into the multidisciplinary management and warrant prospective validation in larger collaborative series.