Long-Term Outcomes After Reirradiation With Spine Stereotactic Body Radiation Therapy: Single-Institutional Retrospective Experience.

Reirradiation of spinal metastases using stereotactic body radiation therapy (SBRT) presents clinical challenges, with limited patient outcomes data to guide decision-making. We report a retrospective, single-institutional experience of 107 lesions treated in 91 patients. Of these, 88 (72%) lesions were initially irradiated with conventional radiation therapy (median equivalent dose of 33 Gy to the target, IQR, 23-35 Gy) with a median time to reirradiation of 12 months (IQR, 4-21 months). For reirradiation, most lesions received either 1 fraction (18-24 Gy) or 3 fractions (30-36 Gy) of SBRT. The median equivalent dose in 2 Gy fractions was 38 Gy (IQR, 30-41 Gy), 27 Gy (22-36 Gy), and 65 (54-73 Gy) for previous courses, reirradiation, and cumulatively, respectively. At 1 year, overall survival was 61% with a cumulative incidence of local failure at 12% and vertebral compression fracture at 9% considering death as a competing risk. None of the 79 treated lesions at L1 or above developed radiation myelitis, but 5 patients developed chronic peripheral neuropathy. In our analysis, most adverse events or local failures occur within the 2 years after retreatment. These findings demonstrate the safety and effectiveness of spine reirradiation with SBRT.