What Factors Predict the Response of Larger Brain Metastases to Radiosurgery?

Abstract BACKGROUND: Approximately 20 to 40% of patients with systemic malignancies develop brain metastases. OBJECTIVE: To assess the potential role of stereotactic radiosurgery (SRS) for larger metastatic brain tumors, we reviewed our recent experience. METHODS: Between 2004 and 2008, 70 patients with a metastatic brain tumor larger than 3 cm in maximum diameter underwent Gamma knife SRS. Thirty-three patients had received previous whole brain radiation therapy (WBRT) and 37 received only SRS. RESULTS: The overall median follow-up was 8.1 months. At the first planned imaging follow-up at 2 months, 29 (41%) tumors had >50% volume reduction, 22 (31%) had 10 to 50% volume reduction, and 19 (28%) were stable or larger. We also evaluated brain edema using MRI T2 images. In 11 patients (16%) the peritumoral edema volume was reduced by more than 50%, in 25 (36%) it was reduced by 10 to 50%, in 21 (30%) it was stable, and in 13 (19%) it was increased. Twenty (36%) discontinued corticosteroids by the time of first imaging follow-up. Because of persistent symptoms, 7 patients (10%) required a craniotomy to remove the tumor. Tumor volume reduction (>50%) was associated with a single metastasis (P = .012), no previous WBRT (P = .002), and a tumor volume 50%) was associated with a single metastasis (P = .024), no previous WBRT (P = .05), and breast cancer histology (P = .044). CONCLUSION: Surgical resection remains the primary approach for larger brain metastases if feasible. Tumor volume is a better indicator than maximum diameter. Tumor volume and edema responded better in patients who underwent SRS alone.