Repeat courses of spine stereotactic radiosurgey (SRS): Efficacy and toxicity
Elibe E, Boyce-Fappiano D, Siddiqui S, Lee I, Rock J, and Siddiqui F. Repeat courses of spine stereotactic radiosurgey (SRS): Efficacy and toxicity. Int J Radiat Oncol Biol Phys 2017; 99(2):E518-E519.
Int J Radiat Oncol Biol Phys
Purpose/Objective(s): Due to recent increased utilization of spine SRS, a unique phenomenon is being observed; spine SRS is being used as a salvage for tumor recurrence after initial SRS treatment. Since limited data is available regarding this subject, our study aims to determine the efficacy and potential consequences of irradiating the spine with two or more courses of SRS. Purpose/Objective(s): 49 patients and 60 re-irradiated spine tumors (83 vertebral bodies) treated at our institution between 6/2001 and 12/2015 were retrospectively reviewed in this Institutional Review Board approved analysis. Each patient received at least two courses of SRS to the same spinal level. 3 patients had three courses of SRS to the same spinal level, and the remaining 46 patients in this study had two courses of SRS. Electronic medical records of clinical exams, and CT/MRI were evaluated. Primary endpoints were pain response, neurological response, radiographic tumor control and the development of any treatment related toxicities. Results: 37 patients (76%) were deceased. Median survival after last SRS treatment was 6.3 months (range 0 days-3.7 years). Follow-up to evaluate clinical (pain and neurological) responses was available for 47 patients, and radiographic follow up for 40 tumors. Median follow-up time was 6.7 months. Time between courses of SRS was an average of 1.4 years (median 1.2 years). Mean number of re-irradiated vertebral bodies was two (range 1-5). Median cumulative dose delivered to a vertebral body was 34 Gy (a median of 18 Gy/1 fx for the first course of SRS and 16 Gy/1 fx for the last course of SRS). For SRS planning, the dose constraint used was 10 Gy to 10% with a maximum point dose of 14Gy]. Cumulative dose delivered to a tumor ranged from 22 Gy-60 Gy. SRS dose range was 8-22 Gy/1 fx. Pain progressed in 6% of tumors. Overall pain response rate was 86% (53% PR, 33% CR), and pain was stable in 8%. Neurological improvement occurred in 73% (18% PR, 55% CR), remained stable in the remaining 27%. 25.6% of tumors showed radiographic evidence of progression. Radiographic tumor control was observed in 72.5% of tumors (55% stable, 17.5% PR). 8 tumors recurred after the last course of SRS. 8 patients experienced adverse effects (including myelomalacia, death, lower extremity weakness, radiculopathy, and minor sensory changes) for which SRS could not be excluded as a potential cause. 56 vertebral compression fractures (VCFs) were observed, 21 of which were potentially SRS induced. Conclusion: Repeat courses of SRS achieved favorable response rates with few toxicities in our cohort. To the best of our knowledge, this is the only reported series analyzing the efficacy and potential consequences of irradiating the spine with multiple courses of SRS.