2485 - Additional Salvage Spine Stereotactic Radiosurgery (SRS) Following Radiographic Progression of Spinal Metastases in Patients Previously Re-Irradiated with SRS

J. J. Bai¹, E. H. Balagamwala², L. Angelov³, J. H. Suh², E. S. Murphy², S. D. Pestak², J. L. Barnhart², S. Johnson², and S. T. Chao²; ¹Case Western Reserve University School of Medicine, Cleveland, OH, ²Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, ³Department of Neurological Surgery, Cleveland Clinic Foundation, Cleveland, OH

Purpose/Objective(s): Re-irradiation with salvage spine stereotactic radiosurgery (sSRS) has emerged as a viable strategy for spinal metastases with progressive disease. We report the characteristics and clinical outcomes of spinal segments that received at least three courses of spine sSRS. Materials/

Methods: 11 spinal segments in 6 patients who received at least three courses of sSRS were evaluated from an IRB-approved retrospective single-institution database. Median overall survival (OS) and time to radiographic failure was calculated by Kaplan-Meier analysis. Radiographic failure was defined as progression on imaging at the treated segment. Toxicity outcomes were collected.
Results: Median follow-up was 8.9 months (range, 0.2 – 46.3). 3 patients died at the time of analysis, with a median OS from final course of sSRS of 66 days (range, 30 - 260). 50% of patients were female, median age at treatment was 63.2 years (range, 36.9 – 77.2), and median consult KPS was 80 (range, 70 – 90). Of the 11 spinal segments treated, 45.5% (5/11) were thoracic, 45.5% (5/11) were lumbar, and 9.1% (1/11) were sacral. The primary cancers were colorectal adenocarcinoma (45.5%; 5/11), NUT midline carcinoma (9.1%; 1/11), lung carcinoid (9.1%; 1/11), renal clear cell carcinoma (27.3%; 3/11), and myxoid liposarcoma (9.1%; 1/11). The median dose for the first sSRS course was 30 Gy/3 fractions (range, 16 – 30 Gy/1-5 fractions). For the second sSRS course, the median dose was 30 Gy/4 fractions (range, 30 Gy/4 fractions – 30 Gy/5 fractions). Median dose for the third course of sSRS was 30 Gy/4 fractions (range, 27 – 30 Gy/4 – 5 fractions). Median cumulative Dmax and D10% to the spinal cord was 58.79 Gy (range, 42.67 – 84.35) and 47.01 Gy (range, 35.61 – 76.62), respectively. Median cumulative Dmax and D10% to the cauda equina was 66.61 Gy (range, 61.73 – 98.2) and 50.69 Gy (range, 45.95 – 72.29), respectively. 37.5% (3/8) of treatments had radiographic progression, at a median time of 13.8 months (range, 2.8 – 14.3). Of these, 33% showed radiographic progression within the paraspinal soft tissues, neural foramen, and pedicles, while 66% showed progression within the epidural space and vertebral body. 37.5% (3/8) of treatments resulted in pain flare, which were all adequately treated with steroids. No cases of vertebral fractures or radiation myelopathy were reported. One patient who received 4 total courses of sSRS to the sacrum/coccyx is currently alive and to date, 99 days since the last course of sSRS, has not experienced any complications nor further radiographic failure.
Conclusion: Three courses of sSRS may be a safe and effective salvage treatment for spinal metastases demonstrating radiographic failure. More investigation is warranted into the clinical characteristics and outcomes of patients who receive at least three courses of sSRS.