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Published on: May 8, 2018
First Report of Staged Adaptive Frameless Stereotactic Radiosurgery in 3 "Pulses" to Salvage Brain Metastases that
Daniel Tong1, Dana Shor1, Beibei Zhang1,2
1Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada.
Background And Objectives:
Staged stereotactic radiosurgery (SRS) for brain metastases (BMets) takes advantage of longer intervals between fractions to reduce treatment-related side effects while maintaining effectiveness. We report our approach for frameless staged SRS consisting of 3 fractions of 8 Gy, 8 Gy, and 4 Gy every 2 weeks as salvage reirradiation of BMets that progressed after previous SRS.
Methods:
Patients treated with frameless staged SRS for both intact and postoperative metastases were identified from our institutional database. Only metastases that failed previous SRS were included. The primary outcome was the rate of radiation necrosis (RN), and secondary outcomes included local failure (LF) and overall survival (OS). Outcomes were calculated using Kaplan-Meier or competing-risks methods. Cox regression and Fine-Gray competing-risks regression were used to identify factors associated with RN, LF, and OS.
Results:
Fifty patients with 89 metastases were treated with staged SRS. The majority were patients with breast (34.8%) and lung (41.6%) cancer. Seventy-seven (86.5%) lesions were intact, and 20 (22.5%) were from radioresistant primaries. Median follow-up was 9.6 months. RN rates were 6.8%, 12.4%, and 13.8% at 6, 12, and 18 months, respectively. At 1 year, 4 (4.5%) RN events were Grade 1 or 2, and 7 (7.9%) were Grade 3. LF and OS rates at 6, 12, and 18 months were 16.1%, 28%, 30.8%, and 81.6%, 60.4%, 42.3%, respectively. On regression analysis, maximum dose within the target lesion as a weighted average (hazard ratio = 1.14 per additional Gy, P = .048) predicted for RN. There was a trend toward worse LF in radioresistant lesions (hazard ratio = 2.09, P = .078). A reduction in target volume was observed in 63% and 75% of all treated lesions between fractions 1 to 2 and 2 to 3, respectively.
Conclusion:
Our staged SRS regimen was an effective and well-tolerated adaptive treatment of reirradiation of BMets with a favorable RN profile.
