2623 - Salvage Fractionated Stereotactic Spine Radiosurgery for Recurrent Metastatic Renal Cell Carcinoma
Presenter(s)
F. Kwong1, S. Perni2, M. C. Tom2, T. Beckham2, B. De2, C. Wang2, D. N. Yeboa2, C. Alvarez-Breckenridge3, R. North3, M. F. F. McAleer2, C. Tatsui3, J. Li2, L. D. Rhines3, and A. J. Ghia2; 1Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 2Department of CNS Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): Stereotactic spinal radiosurgery (SSRS) provides high dose radiation delivery to the target with rapid dose falloff for normal tissue sparing. Renal cell carcinoma (RCC) is a radioresistant histology for which conventional palliative radiation offers limited local control (LC). There are limited data about optimal salvage approaches. In this study, we analyzed our institutional experience of salvage SSRS for RCC spine metastases which recurred after palliative radiation courses.
Materials/Methods: We conducted an IRB approved single-institution retrospective review of patients with biopsy-confirmed RCC and recurrence after initial conventional palliative radiation treatment to spine metastases who received 3- or 5-fraction salvage SSRS (n=20) between 2003-2016. As a comparison group, we analyzed patients with treatment-naïve RCC spine metastases receiving 3- or 5-fraction SSRS (n=75) between 2003-2016. The primary endpoint was LC. Progression was defined using SPINO guidelines. Kaplan-Meier calculations and Cox proportional hazards modeling were used to conduct survival and univariable analyses (UVA).
Results: We identified 20 patients receiving salvage SSRS for recurrent RCC spine metastases. Median age was 60.5 years (range 44-88), and treatment sites were 3 (15%) cervical, 10 (50%) thoracic, and 7 (35%) lumbar spine. 65% of patients had disease at time of treatment. The most common prior radiation regimen was 30Gy in 10 fractions (n=11) with initial dose range of 30-40Gy and fractionation range of 10-20. Median time to salvage was 10 months (range 4-35). 65% received 3-fraction salvage SSRS and 35% received 5-fraction salvage SSRS. Median dose was 27Gy (range 27-30). Median cumulative biologically effective dose (BED) was 90Gy (range 86-102). 7 (35%) patients experienced progression. 1-year LC was 81%, median LC time was 20 months (95% CI 7-NR), and median overall survival (OS) was 15.5 months (95% CI 9-21). On UVA for LC, there were no statistically significant associations with age, gender, spine site, presence of epidural disease, or cumulative BED. As a comparison group, we identified 75 patients with treatment-naïve RCC spine metastases receiving SSRS. Between these groups, there were no statistically significant differences in age, gender, spine site, or presence of epidural disease. Median dose was 27Gy (range 24-30) delivered as either 3- or 5-fraction SSRS. 37 (49%) patients experienced progression. 1-year LC was 64% with a median LC of 27 months (95% CI 13-34) and a median OS of 22 months (95% CI 15-28). On UVA for LC between cohorts, there was no effect of prior radiation.
Conclusion: We found high LC rates with salvage SSRS for RCC spine metastases after conventional palliative radiation, which compares favorably to upfront fractionated SSRS treatment for radiation-naïve metastases. Future analyses will focus on larger samples to evaluate optimal regimens.