Minimized Doses for Linear Accelerator Radiosurgery of Brainstem Metastasis

Purpose Treatment of cerebral metastases located inside the brainstem remains a challenge, as the brainstem is considered to be a neurological organ at risk, whatever the treatment strategy. We report a retrospective study of 30 consecutive patients treated in our institution between 2005 and 2007 with micromultileaf linear accelerator (LINAC) –radiosurgery for brainstem metastases, with reduced doses compared to those usually reported in the literature. Methods and Materials Mean follow-up was 311 days (range, 41–1351). Median age was 57 years (range, 37–82), Mean Karnofsky Index (KI) was 80. Primary tumor site was lung ( n = 13), breast ( n = 4), kidney ( n = 4), skin (melanoma; n = 3), and others (n = 6). Primary tumor was controlled in 17 cases; extracranial metastases were controlled in 12 cases. Mean number of metastases was 1.46 (one to three); median volume was 2.82 cc (0.06–18). Dose was delivered by a micromultileaf collimator 6-MV LINAC . Results Dose administered at the 70% isodose was 13.4 Gy (range, 8.2–15). Median survival was 10 months. Local control rates at 3, 6, and 12 months were 100%, 100%, and 79% respectively. Median neurological control duration was 5 months. Neurological control rates at 3, 6, and 12 months were 73%, 42%, and 25%, respectively. No parameter was found to significantly correlate with survival, local, or cerebral control. No patients had severe side effects (Grade III–IV), according to the Radiation Therapy Oncology Group (RTOG) scale. Conclusion Lower doses than previously reported can achieve the same local control and survival rates in brain metastases, with minimal side effects.