Stereotactic radiosurgery: A new paradigm for melanoma and renal cell carcinoma spine metastases.

Abstract

2030 Background: Renal cell carcinoma (RCC) and melanoma metastatic to the spine present an especially vexing clinical scenario because responses to conventionally fractionated palliative radiotherapy are particularly poor. The advent of image guided treatment techniques, coupled with intensity modulated radiotherapy, have provided the mechanism to deliver high-dose single-fraction radiation safely to spinal metastases. We hypothesized that high dose single fraction radiation (spine SRS) would provide excellent radiographic local control and symptom palliation. Methods: All patients with metastatic RCC (n = 50) or melanoma (n = 30) treated with spine SRS between 2004-2008 were assessed prospectively every 3-4 months until death with serial MRI or CT spine imaging, visual analogue pain scale (VAS), narcotic use, and American Spine Injury Association (ASIA) scores. Each case was assessed for suitability in a multidisciplinary spine clinic or conference. No patient had previous surgery or radiation at the site of interest. Patients received 18-24 Gy in a single fraction (median 24 Gy). Actuarial statistical analyses were performed. Results: The overall median survival was 9 months (2-56 months). Ninety percent of patients achieved radiographic local control and 90% achieved durable symptom palliation. There was no difference in clinical outcome based upon histology (92% RCC vs. 89% Melanoma, p = 0.5). When the dose of radiation was assessed, there was a trend of worse outcomes in the low dose cohort (18-22Gy) when compared to the high dose group (24 Gy), 77% vs. 96% achieved durable local control (p = 0.12). All melanoma patients who received less than 24 Gy (mean 18Gy) experienced local relapse (p = 0.012). Toxicity was limited to grade 1 or 2 complications, and no spinal cord injury was encountered. Conclusions: While the long term local control of melanoma and renal cell carcinoma spine metastases is reported in the range of 30%-40% with conventionally fractionated radiotherapy, spine SRS appears to prove very high tumor control for even highly radioresistant histologies with minimal toxicity. High dose spine SRS (24 Gy) provides better results than lower dose treatment, especially for melanoma patients. No significant financial relationships to disclose.