Effect of Single-Fraction vs Multifraction Radiotherapy on Ambulatory Status Among Patients With Spinal Canal Compression From Metastatic Cancer

Abstract

IMPORTANCE Malignant spinal canal compression, a major complication of metastatic cancer, is managed with radiotherapy to maintain mobility and relieve pain, although there is no standard radiotherapy regimen. OBJECTIVE To evaluate whether single-fraction radiotherapy is noninferior to 5 fractions of radiotherapy. DESIGN, SETTING, AND PARTICIPANTS Multicenter noninferiority randomized clinical trial conducted in 42 UK and 5 Australian radiotherapy centers. Eligible patients (n = 686) had metastatic cancer with spinal cord or cauda equina compression, life expectancy greater than 8 weeks, and no previous radiotherapy to the same area. Patients were recruited between February 2008 and April 2016, with final follow-up in September 2017. INTERVENTIONS Patients were randomized to receive external beam single-fraction 8-Gy radiotherapy (n = 345) or 20 Gy of radiotherapy in 5 fractions over 5 consecutive days (n = 341). MAIN OUTCOMES AND MEASURES The primary end point was ambulatory status at week 8, based on a 4-point scale and classified as grade 1 (ambulatory without the use of aids and grade 5 of 5 muscle power) or grade 2 (ambulatory using aids or grade 4 of 5 muscle power). The noninferiority margin for the difference in ambulatory status was -11%. Secondary end points included ambulatory status at weeks 1, 4, and 12 and overall survival. RESULTS Among 686 randomized patients (median [interquartile range] age, 70 [64-77] years; 503 (73%) men; 44% had prostate cancer, 19% had lung cancer, and 12% had breast cancer), 342 (49.8%) were analyzed for the primary end point (255 patients died before the 8-week assessment). Ambulatory status grade 1 or 2 at week 8 was achieved by 115 of 166 (69.3%) patients in the single-fraction group vs 128 of 176 (72.7%) in the multifraction group (difference, -3.5%[1-sided 95% CI, -11.5% to infinity]; P value for noninferiority = .06). The difference in ambulatory status grade 1 or 2 in the single-fraction vs multifraction group was -0.4%(63.9% vs 64.3%; [1-sided 95% CI, -6.9 to infinity]; P value for noninferiority = .004) at week 1, -0.7%(66.8% vs 67.6%; [1-sided 95% CI, -8.1 to infinity]; P value for noninferiority = .01) at week 4, and 4.1% (71.8% vs 67.7%; [1-sided 95% CI, -4.6 to infinity]; P value for noninferiority = .002) at week 12. Overall survival rates at 12 weeks were 50% in the single-fraction group vs 55% in the multifraction group (stratified hazard ratio, 1.02 [95% CI, 0.74-1.41]). Of the 11 other secondary end points that were analyzed, the between-group differences were not statistically significant or did not meet noninferiority criterion. CONCLUSIONS AND RELEVANCE Among patients with malignant metastatic solid tumors and spinal canal compression, a single radiotherapy dose, compared with a multifraction dose delivered over 5 days, did not meet the criterion for noninferiority for the primary outcome (ambulatory at 8 weeks). However, the extent to which the lower bound of the CI overlapped with the noninferiority margin should be considered when interpreting the clinical importance of this finding.