Phase 1 trial shows feasibility of 3D CRT plus SBRT boost for metastatic spinal cord compression

PURPOSE: Palliative 3D-conformal radiation therapy (3D CRT) is the standard treatment for metastatic epidural spinal cord compression (MESCC) in nonsurgical candidates, but pain, motor, and neurologic outcomes are variable. We conducted a pilot study to determine feasibility of stereotactic body radiation therapy (SBRT) boost following 3D CRT and characterize impact on outcomes. METHODS AND MATERIALS: Eligible patients included those with a solid malignancy, evidence of at least Bilsky 1b MESCC, and Rades motor scale function of at least 3. Patients were initially treated with 3D CRT (either 20 Gy/5 or 8 Gy/1) followed by SBRT boost within 6 weeks to a dose of 18 to 24 Gy/2. The primary outcome was feasibility of planning and delivery of 3D CRT and SBRT boost, with a success rate defined as 80% of accrued patients (95% CI, 75%-97%). RESULTS: Sixteen patients were initially accrued from 2018 to 2022. Thirteen patients were treated successfully with SBRT boost following 3D CRT, meeting the primary outcome (0.81, 0.57-0.93). Motor function was maintained in 76.9% and improved by 2 points from baseline in 15.4% of patients at 1-month post-SBRT . Ambulatory function improved at 1, 3, and 6 months post-SBRT in 15.4%, 18.2%, and 12.5% of patients respectively. Pain improved in 7.7%, 27.3%, and 37.5% of patients at 1, 3, and 6 months. Only 1 grade 3 toxicity (chest wall pain) occurred, which resolved at 3 months. Median global quality of life using European Organization of Research and Treatment of Cancer Quality of Life Questionnaire-Core-30 improved from baseline of 69.2, to 76.3, 76.6, and 82.5 at 1, 3, and 6 months, respectively. European Organization of Research and Treatment of Cancer-Bone Metastasis 22 scores improved in functional and pain domains at 1, 3, and 6 months. CONCLUSIONS: SBRT boost following 3D CRT for MESCC was feasible, with no added neurologic toxicity, and resulted in moderate improvements from baseline or prolonged maintenance of motor, ambulatory function, and pain control, with suggestion of improved quality of life over time.