Therapeutic effect of linac-based stereotactic radiotherapy with a micro-multileaf collimator for the treatment of patients with brain metastases from lung cancer

Objective: To assess the efficacy of hypofractionated linac-based stereotactic radiotherapy with a micro-multileaf collimator (mMLC) in lung cancer patients with brain metastases. Methods: Seventy-eight lesions of brain metastases in 49 lung cancer patients treated by stereotactic radiotherapy between September 2003 and December 2006 were analyzed. In the treatment planning, the planning target volume (PTV) was defined as an enhanced lesion plus 3 mm margin. A total dose of 39-42 Gy in three fractions was delivered to the isocenters of the PTV. Results: The median survival time after stereotactic radiotherapy was 17.4 months. The 1- and 2-year survival rates were 61% and 32%, respectively. The presence of extracranial tumors, the pre-treatment performance status, and the Radiation Therapy Oncology Group recursive partitioning analysis class were significant prognostic factors. The 1-and 2-year local recurrence rates were 14% and 17%, respectively, with no serious acute toxic effect. Injuries involving brain necrosis were observed in six patients. New brain metastases or meningeal carcinomatosis was seen in more than half of the patients following treatment with stereotactic radiotherapy. Conclusions: Hypofactionated stereotactic radiotherapy with mMLC is considered to be an effective and safe modality for the treatment of brain metastases in lung cancer patients.