Functional outcome and survival after radiotherapy of metastatic spinal cord compression in patients with cancer of unknown primary

Purpose: Patients with cancer of unknown primary (CUP) account for about 10% of patients with metastatic spinal cord compression (MSCC). This study aims to define the appropriate radiation regimen for these patients. Methods and Materials: Data of 143 CUP patients irradiated for MSCC were retrospectively evaluated. Short-course radiotherapy (RT) (1×8 Gy, 5×4 Gy, n = 68) and long-course RT (10×3 Gy, 15×2.5 Gy, 20×2 Gy, n = 75) plus 8 further potential prognostic factors (age, gender, performance status, visceral metastases, other bone metastases, number of involved vertebrae, ambulatory status, time of developing motor deficits before RT) were compared for functional outcome and survival. Results: Improvement of motor function occurred in 10% of patients, no further progression of motor deficits in 57%, and deterioration in 33%. On multivariate analysis, functional outcome was positively associated with slower development of motor deficits (p < 0.001), absence of visceral metastases (p = 0.008) and other bone metastases (p = 0.027), and ambulatory status (p = 0.054), not with the radiation regimen (p = 0.74). Recurrence of MSCC in the irradiated region occurred in 7 patients after median 6 months. Median survival was 4 months. On multivariate analysis, better survival was significantly associated with absence of visceral metastases (p < 0.001), absence of other bone metastases (p = 0.005), ambulatory status (p = 0.001), and slower development of motor deficits (p = 0.030). Conclusions: For MSCC treatment in patients with CUP, no significant difference was observed between short-course and long-course RT regarding functional outcome and survival. Short-course RT appears preferable, at least for patients with a poor predicted survival, as it is more patient convenient and more cost-effective.