Stereotactic body radiation therapy for oligometastatic ovarian cancer: a step toward a drug holiday

Purpose: To evaluate stereotactic body radiation therapy (SBRT) for metachronous oligometastatic ovarian cancer patients in terms of local control, delay of systemic treatment, survival outcomes, and toxicity. Methods and Materials: Retrospective data collection from a single institution was performed. The inclusion criteria were as follows: (1) oligorecurrent or oligoprogressive disease in ovarian cancer patients during or after systemic therapy; (2) surgery or other local therapies not feasible; and (3) relative contraindication to systemic therapy for reasons such as unavailability of additional chemotherapy lines or refusal of the patient. Tumor response and toxicity were evaluated using the Response Evaluation Criteria in Solid Tumors and the Common Terminology Criteria for Adverse Events version 4.03, respectively. A new systemic therapy regimen was started after an SBRT treatment course in 57 of 109 cases (52.3%). Local progression–free survival, progression-free survival, and overall survival were calculated via the Kaplan-Meier method. The systemic treatment–free interval was calculated in cases without concomitant systemic therapy. Results: Between May 2012 and December 2016, 82 patients (156 lesions) underwent SBRT with a median dose of 24 Gy in 3 fractions. The median follow-up period was 17.4 months. Patients received a median of 3 systemic therapy regimens prior to SBRT. Concomitant systemic therapy was performed for 29 lesions (18.6%). Among 152 evaluable lesions, a complete radiologic response, partial response, stabilization, and progressive disease were observed in 91 (60%), 26 (17%), 24 (16%), and 11 (7%), respectively. No grade 3 or 4 acute or late toxicities were observed. The median systemic treatment–free interval after SBRT was 7.4 months, and 1 of 3 patients was disease free at 1 year after SBRT. The actuarial 2-year local progression–free survival, progression-free survival, and overall survival rates were 68%, 18%, and 71%, respectively. The pattern of failure was predominantly out of field. Conclusions: SBRT for oligometastatic ovarian cancer showed good local control and a good toxicity profile. It might be an appealing alternative to other invasive local therapies to delay systemic therapy in the case of chemorefractory disease or intolerance to systemic agents.