Local disease control after decompressive surgery and adjuvant high-dose single-fraction radiosurgery for spine metastases

Abstract

Object Adjuvant radiation following epidural spinal cord decompression for tumor is a powerful tool used to achieve local disease control and preserve neurological function. To the authors' knowledge, only 1 published report addresses adjuvant stereotactic radiosurgery after this procedure, but that study used significantly lower doses than are currently prescribed. The authors review their experience using high-dose single-fraction radiosurgery as a postoperative adjuvant following surgical decompression and instrumentation to assess long-term local tumor control, morbidity, and survival. Methods A retrospective chart review identified 21 patients treated with surgical decompression and instrumentation for high-grade, epidural, spinal cord compression from tumor, followed by single-fraction high-dose spinal radiosurgery (dose range 18–24 Gy, median 24 Gy). Spinal cord dose was limited to a cord maximal dose of 14 Gy. Tumor histologies, time between surgery and radiosurgery, time to local recurrence after radiosurgery as assessed by serial MR imaging, and time to death were determined. Competing risk analysis was used to evaluate these end points. Results In this series, 20 tumors treated (95%) were considered highly radioresistant to conventional external beam radiation. The planning target volume received a high dose (24 Gy) in 16 patients (76.2%), and a low dose (18 or 21 Gy) in 5 patients (23.8%). During the study, 15 (72%) of 21 patients died, and in all cases death was due to systemic progression as opposed to local failure. The median overall survival after radiosurgery was 310 days (range 37 days to not reached). One patient (4.8%) underwent repeat surgery for local failure and 2 patients (9.5%) underwent spine surgery for other reasons. Local control was maintained after radiosurgery in 17 (81%) of 21 patients until death or most recent follow-up, with an estimated 1-year local failure risk of 9.5%. Of the failures, 3 of 4 were noted in patients receiving low-dose radiosurgery, equaling an overall failure rate of 60% (3 of 5 patients) and a 1-year local failure estimated risk of 20%. Those patients receiving adjuvant stereotactic radiosurgery with a high dose had a 93.8% overall local control rate (15 of 16 patients), with a 1-year estimated failure risk of 6.3%. Competing risk analysis showed this to be a significant difference between radiosurgical doses. One patient experienced a significant radiation-related complication; there were no wound-related issues after radiosurgery. Conclusions Spine radiosurgery after surgical decompression and instrumentation for tumor is a safe and effective technique that can achieve local tumor control until death in the vast majority of patients. In this series, those patients who received a higher radiosurgical dose had a significantly better local control rate.