Evaluation of Five Radiation Schedules and Prognostic Factors for Metastatic Spinal Cord Compression

Abstract

To study five radiotherapy (RT) schedules and potential prognostic factors for functional outcome in metastatic spinal cord compression (MSCC). One thousand three hundred four patients who were irradiated from January 1992 to December 2003 were included in this retrospective review. The schedules of 1 x 8 Gy in 1 day (n = 261), 5 x 4 Gy in 1 week (n = 279), 10 x 3 Gy in 2 weeks (n = 274), 15 x 2.5 Gy in 3 weeks (n = 233), and 20 x 2 Gy in 4 weeks (n = 257) were compared for motor function, ambulatory status, and in-field recurrences. The following potential prognostic factors were investigated: age, sex, performance status, histology, number of involved vertebra, interval from cancer diagnosis to MSCC, pretreatment ambulatory status, and time of developing motor deficits before RT. A multivariate analysis was performed with the ordered logit model. Motor function improved in 26% (1 x 8 Gy), 28% (5 x 4 Gy), 27% (10 x 3 Gy), 31% (15 x 2.5 Gy), and 28% (20 x 2 Gy); and posttreatment ambulatory rates were 69%, 68%, 63%, 66%, and 74% (P = .578), respectively. On multivariate analysis, age, performance status, primary tumor, involved vertebra, interval from cancer diagnosis to MSCC, pretreatment ambulatory status, and time of developing motor deficits were significantly associated with functional outcome, whereas the RT schedule was not. Acute toxicity was mild, and late toxicity was not observed. In-field recurrence rates at 2 years were 24% (1 x 8 Gy), 26% (5 x 4 Gy), 14% (10 x 3 Gy), 9% (15 x 2.5 Gy), and 7% (20 x 2 Gy) (P < .001). Neither the difference between 1 x 8 Gy and 5 x 4 Gy (P = .44) nor between 10 x 3 Gy, 15 x 2.5 Gy, and 20 x 2 Gy (P = .71) was significant. The five RT schedules provided similar functional outcome. The three more protracted schedules seemed to result in fewer in-field recurrences. To minimize treatment time, the following two schedules are recommended: 1 x 8 Gy for patients with poor predicted survival and 10 x 3 Gy for other patients. Results should be confirmed in a prospective randomized trial.