Clinical Outcomes of Stereotactic Body Radiation Therapy for Extracranial Oligometastatic Ovarian Cancer

Abstract

The purpose of this study was to evaluate the role of stereotactic body radiosurgery (SBRT) for extracranial metastases in patients with ovarian cancer. From March 2009 to June 2018, 33 patients with ovarian cancer of any histology underwent SBRT treatment of 90 extracranial lesions. All patients underwent primary surgical excision at the time of diagnosis and at least one line of chemotherapy. Median age was 63 years (range: 36-84). Dosing regimens included 6 Gy x 4 in 26 (29%), 6 Gy x 3 in 8 (9%), 10 Gy x 3 in 10 (11%), 7 Gy x 3 in 8 (9%), and 12 Gy x 3 in 7 cases (8%). The sites of disease included lymph node (46 lesions), liver (20 lesions), soft tissue (16 lesions), bone (4 lesions), spleen (2 lesions), pancreas (1 lesion), and lung (1 lesion). Response to SBRT was assessed via FDG-PET/CT using PERCIST criteria in 66 cases and via CT imaging using RECIST criteria in 24 cases. Toxicity was assessed via the RTOG/EORTC criteria. Median follow-up was 54.6 months. Imaging completed 3 months after treatment showed a complete response (CR) in 59 cases (66%), partial response (PR) in 16 cases (18%), stable disease (SD) in 13 cases (14%), and progressive disease in 2 cases (2%). Patients with nodal lesion were more likely to achieve CR when compared to liver lesions (p=0.02, 78.3% vs 55.0%) and soft tissue lesions (p= 0.046, 78.3% vs 50.0%). Local control (LC) was 80% at 5 years, and multivariate analysis revealed that achieving CR (p=0.016) correlated with improved LC. The median systemic treatment-free interval, median progression-free survival (PFS), and median overall survival (OS) were 8 months, 3.3 months, and 49.6 months, respectively. Achieving CR was associated with improved OS (p=0.001, 5-year OS 54% vs 30%) and improved PFS (p=0.014, 1-year PFS 22% vs 7%). Overall acute toxicity occurred in 27 cases (30%), and all of which were grade 1 or 2. This analysis suggests that SBRT is a well-tolerated and effective treatment option for oligometastatic ovarian cancer, providing durable local control with the potential to delay systemic treatment. Patients who achieved CR were shown to have improved LC, PFS, and OS.