Outcomes Following Spine Stereotactic Radiosurgery for the Treatment of Melanoma Spine Metastases

Abstract

With new targeted and immunotherapies improving survival among patients with metastatic melanoma, the prevalence of metastatic disease within the spine is likely to increase. Spine stereotactic radiosurgery (sSRS) as a palliative treatment strategy for spinal metastasis allows for dose escalation, which may improve the therapeutic ratio of radioresistant tumors such as melanoma. We sought to evaluate the outcomes of patients with spinal metastasis from primary melanoma treated with sSRS. Patients who were diagnosed with metastatic melanoma to the spine and underwent sSRS with at least 1 month of follow-up were included. Clinical and treatment data, including initial consultation notes, disease characteristics, prior surgery and radiotherapy (including sSRS) were collected. The primary outcome was pain relief. Secondary outcomes included pain progression- and radiographic failure-free survival. Actuarial outcomes were assessed with Kaplan-Meier analysis. Cox proportional hazards modeling was utilized to evaluate the association between clinical and treatment factors with treatment outcomes. From our database of over 700 treatments, 36 treatments in 15 patients met inclusion criteria. One patient had metastatic uveal melanoma whereas 14 had metastatic cutaneous melanoma. Median KPS was 80 (range, 70-90). Median prescription dose was 16 Gy (range, 12-30 Gy) in 1 fraction (range, 1-5 fractions) with a median follow-up time of 5 months (range, 2.1-66.1 months). Median time to pain relief was 1.28 months. Cumulative incidence of pain relief at 1, 3, and 12 months were 3.2%, 77.0%, and 92.3%, respectively. Pain progression- and radiographic failure-free survival at 1, 3, and 12 months were 94.4%, 73.9%, and 73.9%, and 100%, 84.8%, and 84.8%, respectively. Overall, 11% of treatments developed radiographic failure with a median time to failure of 2.6 months (range, 1.6-2.8 months). Crude rates of pain flare and vertebral compression fracture after sSRS were 22.2% and 25%, respectively. Univariate analysis did not identify any disease or treatment characteristics that predicted for pain progression or radiographic failure after sSRS. sSRS for metastatic melanoma provides very favorable and durable radiographic and pain control. Due to the limited number of treatments in this series, caution must be utilized in interpreting the pain flare and vertebral compression fracture rates.