The role of spinal stereotactic radiosurgery in the treatment of renal cell carcinoma spinal metastases

OBJECTIVE: Renal cell carcinoma (RCC) spinal metastases can lead to intractable pain and neurological deficits and are traditionally considered radioresistant to conventional radiotherapy. Spinal stereotactic radiosurgery (SRS) has emerged as a minimally invasive management modality to deliver high doses of conformal radiation while sparing critical structures to overcome radioresistance. The aim of this large, single-institution study was to evaluate outcomes following SRS for patients with RCC spinal metastases. METHODS: Eighty-one patients who underwent SRS for 152 primary RCC spinal metastases met inclusion criteria. The primary outcome was local control (LC). Secondary outcomes were overall survival (OS), pain palliation, and adverse radiation effects (AREs). Univariable and multivariable Cox proportional hazards regression analyses were conducted to assess prognostic factors related to study outcomes. RESULTS: At a median follow-up of 10 (range 1-125) months, 40 lesions (26%) demonstrated radiographic progression. The median time to progression was 9 (range 3-60) months. Following SRS, the 6-month, 1-year, and 2-year crude LC rates were 91%, 78%, and 65%, respectively. The median OS was 15 (range 1-129) months, with rates of 6-month, 1-year, and 2-year OS of 84%, 57%, and 39%, respectively. Tumors with extension into the paraspinal musculature (HR 2.70, 95% CI 1.17-6.26; p = 0.020) and those causing radiographic spinal misalignment (HR 3.79, 95% CI 1.43-10.06; p = 0.008) were associated with worsened LC. No predictors were found for OS. Clinical improvement or stability in pain was observed in 97%, 88%, and 81% of lesions at 1, 3, and 6 months after SRS, respectively. Twenty-six AREs (17%) were observed, including 14 vertebral compression fractures (VCFs, 9%). Baseline VCF at the irradiated level (HR 6.00, 95% CI 1.29-27.87; p = 0.023) was significantly associated with VCF following SRS. CONCLUSIONS: Spinal SRS is a safe and effective treatment modality that confers high rates of tumor control and symptomatic pain relief for patients with RCC spinal metastases.