Does facility volume influence survival in patients with primary malignant bone tumors of the vertebral column? A comparative cohort study.

Background Context: Facility volume has been correlated with survival in many cancers. This relationship has not been established in primary malignant bone tumors of the vertebral column (BTVC).
Purpose: To investigate whether facility patient volume is associated with overall survival in patients with primary malignant BTVCs.
Study Design: Retrospective comparative cohort.
Patient Sample: Adult patients with chordomas, chondrosarcomas, or osteosarcomas of the mobile spine.
Outcome Measures: Five-year survival.
Methods: We retrospectively analyzed 733 patients with primary malignant BTVCs in the national cancer database from 2004 through 2015. Univariate and multivariate analyses were used to correlate specific outcome measures with facility volume. Volume was stratified based on cumulative martingale residuals to determine the inflection point of negative to positive impact on survival based on the patient cohort. Long-term survival was compared between patients treated at high and low volume using the Kaplan-Meier method. Only patients with malignant primary tumors were considered eligible for inclusion; patients with incomplete treatment data or benign tumors were excluded.
Results: Patients treated at high-volume centers (HVCs) were younger (p=.0003) and more likely to be insured (p<.0001). There were no significant differences in tumor characteristics. Patients treated at high-volume facilities had improved 5-year survival of 71% versus 58% at low-volume centers (p<.0001). Patients treated at HVCs were more likely to receive surgical treatment (91% vs. 80%, p<.0001); if surgery was performed, they were more likely to undergo an en bloc resection (48% vs. 30%, p<.0001). However, there were no differences in margin status or utilization of radiotherapy or chemotherapy between HVCs and low-volume centers. In a multivariate analysis, facility volume was independently associated with improved survival overall (HR 0.75 [0.58-0.97], p=.03).
Conclusions: Primary malignant BTVCs are rare, even for HVCs. Despite this, patient survival was significantly improved when treatment was performed at HVCs.
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