Results of linac-based stereotactic radiotherapy for brain metastasis

Objective: To determine the effect of stereotactic radiotherapy(SRT) or X-knife on the clinical course of brain metastasis. Methods: From March 2001 to July 2004, 98 patients with brain me- tastases were treated with 6 MV linear accelerator based SRT. All patients had pathological diagnosis of the primary focus or the metastatic focus. Comparision of the focus on CT/MRI taken immediately before and 6 months after treatment was made. Results: The follow-up duration ranged from 12-52 months (mean 30 months), and the follow-up rate was 94%. The overall median survival in this series was 10 months, and 1-year survival was 41%. Median survival in patients with a single focus was 12 months, and 1-year survival was 45%, while those with multiple focuses was 7 months and 38% respectively (P =0.181). Clinical syndrome was relieved in 83%. Focus control (CR + PR) was observed in 82% of 111 brain metastatic focuses after follow-up of more than 6 months. Focus control of focuses ≤14.1 cm3 and > 14.1 cm3 was 85% and 60% respectively demonstrating a difference of P=0.029. There were 21 focuses with necrosis in the cen- ter, and their focus control was 62%. There was significant difference between lesions with and without (87%) necrosis (P=0.013). And the focus control was not related with pathological diagnosis. Conclusions: Stereotactic radiotherapy may prolong the medium survival time in patients who suffer from brain metastasis with any kind of pathological diagnosis. Local focus control of the brain metastatic tumor ≤14.1 cm3 is higher. (authors)