Stereotactic radiosurgery for primary malignant spinal tumors.

OBJECTIVES: We adopted stereotactic radiosurgery (SRS) to treat primary malignant spinal tumors. The objective of this study was to evaluate local control rate and to identify prognostic factors after SRS for primary malignant spinal tumors.

METHODS: Medical records and radiological data for 29 patients with primary malignant spinal tumors were retrospectively analyzed. The histological diagnoses were chordoma (11 cases), chondrosarcoma (5 cases), osteosarcoma (3 cases), synovial sarcoma (3 cases), plasmacytoma (2 cases), Ewing sarcoma (2 cases), malignant peripheral nerve sheath tumor (2 cases), and malignant fibrous histiocytoma (1 case). Patient age ranged from 11 to 68 years (median, 46 years). Surgical resection and percutaneous biopsy were chosen as initial treatments in 25 and 4 cases, respectively. Stereotactic radiosurgery was used as primary treatment method in 14 cases and as a salvage treatment for progressed lesions in 15 cases. Distant metastasis was noted in two sarcoma patients. Eleven patients had undergone previous conventional external beam radiation therapy (cEBRT) before SRS. Overall survival, local progression-free survival, and the prognostic factors affecting local recurrence were investigated.

RESULTS: Tumor volume ranged from 2·0 to 235 cc (median, 14 cc). Delivered radiation doses were from 12 to 50 Gy with two to six sessions. The mean radiation dose converted into a biological effective dose (BED) was 60 Gy (range, 43-105 Gy). The mean follow-up period was 50 months (range, 8-126 months). The mean overall survival was 84 months for chordoma patients and 104 months for sarcoma patients. No factors that affected overall survival were found. The mean local progression-free survival was 56 months for chordoma patients and 73 months for sarcoma patients. The recurrent mode of presentation was predictive of local progression of spinal sarcomas (P  =  0·009). However, in chordoma patients, no factors were found to correlate with local recurrence.

CONCLUSION: These preliminary results suggest that SRS could provide good local control when applied as postoperative adjuvant or salvage treatment after cEBRT for primary malignant spinal tumors.