Stereotactic radiosurgery for brain metastases using a linac system: evaluation of initial local response by imaging

We analyzed the efficacy of initial local response of MBT by imaging obtained within two months after treatment, to determine if there are factors that may be important for the initial local response of the disease. If an earlier local tumor response can be expected from SRS, patients with a poor prognosis should be treated with this modality.

Thirty-six patients with 59 lesions were treated by linac radiosurgery. The primary tumor, peripheral dose, tumor volume, and CT enhancement pattern of the tumor before treatment (homogeneous or ring-enhancing) were chosen as factors related to local tumor response and were used in the statistical analysis.

1) The initial local response of radiation-resistant tumors to conventional EBRT was worse than that of other tumors. The initial local responses of MBT from breast carcinoma, colon carcinoma, and pulmonary carcinoma were good. 2) Excluding radioresistant tumors, the cases irradiated at 25 Gy or more tended to show good local control. 3) No statistically significant differences were found between local response and factors such as the enhancement pattern and tumor volume in the analysis of MBT.