Evaluation of MRI findings and short-term outcome in lung cancer patients with brain metastases after stereotactic radiotherapy

Objective: To evaluate the treatment outcomes in lung cancer patients with brain metastases (BM) after stereotactic radiotherapy (SRT) according to magnetic resonance imaging (MRI) findings and the Response Evaluation Criteria In Solid Tumors (RECIST). Methods: A retrospective analysis was performed on 31 lung cancer patients with 60 BM lesions who were treated with SRT. Tumor responses were evaluated according to MRI findings and the RECIST. Results: The MRI after SRT showed that (1) 14 lesions recurred, with nodular enhancement in 8 lesions, homogeneous enhancement in 5 lesions, and inhomogeneous enhancement in 1 lesion; (2) 11 lesions (18%) had suspected progression, with homogeneous enhancement in 5 lesions, inhomogeneous enhancement in 3 lesions, peripheral enhancement in 2 lesions,and nodular enhancement in 1 lesion; (3) 35 lesions were controlled, with decreased volume or disappearance in 19 lesions, insignificant volume change in 10 lesions, and increased volume in 6 lesions; (4) the overall response rate was 76.7% (suspected progression + controlled). According to the RECIST, 15 lesions (25%) achieved a complete response (CR), 9 lesions (15%) achieved a partial response (PR), 12 lesions (20%) had stable disease,and 24 lesions (40%) had progressive disease, and the response rate (CR + PR) was 40%. Conclusions: There are various MRI findings for brain metastases in lung cancer patients after SRT, and 18% of the lesions are difficult to evaluate by MRI. RECIST underestimates the short-term effect of SRT. (authors)