MET-10 Preliminary report of radiotherapy for brain metastases from breast and kidney using mask system of Leksell Gamma Knife Icon

Object: Leksell Gamma Knife Icon enables us to apply new methods of immobilization using mask fixation and the option of fractionated treatment. This provides exceptional accuracy and precision of radiosurgery, making it a possibility for many more disease types and many more patients to be treated. Methods: We retrospectively analyzed 97 patients (140 times) with brain metastases from breast (B group) and 26 patients (33 times) with brain metastases from kidney (K group) and who underwent Gamma Knife Icon using mask fixation between September 25th, 2017 and June 30th, 2020 at Rakusai Shimizu Hospital. Patients with small, few, newly diagnosed, and non-eloquent area tumors were treated in a single session. If the tumor volume was larger than 5.0 ml, recurrence, or the location was in an eloquent area, we applied a fractionated schedule. If the tumor number was large, we selected a multisession schedule. Median tumor number was three (1–64) in B group and two (1–31) in K group. Median tumor size was 2.7 (0. 01-58.8) ml in B group and 2.8 (0.02–123.5) ml in K group. We selected fractionated schedules as follows; 7.0 Gy x 5Fr (5–10 ml), 4.2Gy x 10Fr (10-20ml), 3.7Gy x 10Fr (20-30ml), 3.2Gy x 10Fr (30ml-). Results: 32 (B) and 14 (K) cases were treated in a single session, 80 (B) and 17 (K) with fractionation, and 28 (B) and 2 (K) with multiple sessions. Median survival times after Icon treatment was 28.2 (B) and 15.5 (K) months. Local control rates were 89 % (B) and 85% after 12-month Icon treatment. Qualitative survival rates were 91% (B) and 86% (K) after 12-month Icon treatment. There were no statistically differences between two groups. Conclusions: Although these results are limited to short periods, survival rates, local control rates and qualitative survival rates were within the acceptable ranges.