Involved-field radiation therapy for recurrent ovarian cancer: Results of a multi-institutional prospective phase II trial

Objective: To evaluate the efficacy and safety of involved-field radiation therapy (IFRT) in patients with locoregionally confined recurrent or persistent epithelial ovarian cancer. Methods: This study included patients with recurrent epithelial ovarian cancer eligible for IFRT either during diagnosis of the recurrence or after salvage therapies. IFRT was performed at a dose of ≥45 Gy for all tumors with 10–15-mm margins as seen on standard imaging. The primary endpoint was progression-free survival (PFS); the secondary endpoints were safety, response rate, local control, and overall survival (OS). Results: Thirty patients with a mean number of 5.7 metastatic lesions each were enrolled between 2014 and 2016. Seventeen were treated with 3-D conformal radiation therapy (RT) and 13 with intensity-modulated RT. IFRT was well tolerated in all patients, and acute toxicity ≥ grade 2 was not observed. One case of grade 3 abdominal pain was reported 10 months post-RT. The overall and complete response rates were 85.7% and 50%, respectively. After a median follow-up of 28 (range, 17–42) months, the median PFS was 7 months. The 2-year PFS rate was 39.3%. Six of the 16 patients who developed outfield disease progression after IFRT were successfully treated with repeat IFRT as salvage treatment. The 3-year local control and OS rates were 84.4% and 55.8%, respectively. Conclusions: Although the primary endpoint was not met, IFRT might be safe and effective for in-field tumor control in patients with persistent epithelial ovarian cancer with a limited number of metastatic foci. We plan to conduct a larger scale multi-center phase II prospective study.