Applicability of RECIST1.1, MDACC and SPINO Tumor Response Criteria After Adjuvant Stereotactic Spinal Radiosurgery in Surgically Treated Spinal Metastases.

Background and Objectives: Up to 40% of patients with cancer develop spinal metastases, and stereotactic spinal radiosurgery (SSRS) achieves high local control rates as definitive or postoperative treatment. Multiple tumor response assessments have been used but their compared clinical performance in post-surgical patients remains unclear. We sought to compare the applicability of RECIST1.1, MDACC and SPINO criteria. Materials and Methods: This IRB-approved retrospective study included patients with high-grade epidural spinal cord compression treated with decompressive surgery followed by adjuvant SSRS, with MRI follow-up available. Lesions were classified according to each of the scale's objective (RECIST1.1 and MDACC) and subjective (SPINO [radiology reports]) criteria. Results: Ninety-four treated levels in 93 patients (median age 58.9 years) were analyzed. Most metastases were thoracic, and all cases had preoperative high-grade epidural spinal cord compression. Adjuvant SSRS was delivered in one or three fractions. Median follow-up was 16 months (range, 1-132), SPINO-based assessment was feasible in 100% of cases, RECIST1.1 in 43.6% and MDACC in 46.8%. Progressive disease criteria were met in 21.3% of cases using SPINO-based assessment, 19.5% using RECIST1.1, and 6.8% using MDACC. Conclusions: The SPINO recommendations provide a practical and comprehensive framework for radiographic response assessment in monitoring spinal metastases treated with a combination of surgical decompression and adjuvant SSRS.