Is Treatment at a High-volume Center Associated with an Improved Survival for Primary Malignant Bone Tumors?
Authors: Malik Azeem Tariq , Alexander John H. , Khan Safdar N. , Scharschmidt Thomas J. 
Published: November 2019

Abstract

Background
Centralization of cancer care to high-volume facilities has been shown to improve the overall survival of patients with soft-tissue sarcomas. Current evidence regarding the impact of increased hospital volume on treatment patterns and survival rates for patients with primary malignant bone tumors remains limited. Understanding the facility volume-outcome relationship for primary malignant bone tumors will further discussion on ways to promote delivery of quality cancer care across the nation.

Questions/purposes
(1) Is there a difference in overall survival for patients with primary malignant bone tumors undergoing treatment at a high-volume facility (at least 20 patients per year) versus those treated at a low-volume facility (less than 20 patients per year)? (2) Do surgical treatment patterns (limb-salvage versus amputation) and margin status (positive versus negative) vary between high-volume and low-volume facilities?

Methods
The 2004 to 2015 National Cancer Database was queried using International Classification of Disease for Oncology topographical codes to identify patients undergoing treatment (surgery, chemotherapy, and/or radiation therapy) for primary malignant bone tumors of the extremities (C40.0-C40.3, C40.8, and C40.9) or pelvis (C41.4). Histologic codes were used to group the tumors into the following categories: osteosarcomas, Ewing’s sarcomas, chondrosarcomas, chordomas, and other or unspecified. Patients who did not receive any treatment (surgery, chemotherapy, and/or radiotherapy) at the reporting facility were excluded from the study. Facility volume was calculated based on the average number of patients per year for the entire study period. A preliminary stratified Cox regression model was used to identify evidence-based thresholds or cutoffs for high-volume and low-volume facilities, while adjusting for differences in patient, tumor, and treatment characteristics. We identified high-volume facilities as those treating at least 20 patients per year and low-volume facilities as those treating fewer than 20 patients per year. A Kaplan-Meier survival analysis was used to report overall unadjusted 5-year survival rates at high-volume and low-volume facilities. Multivariate Cox regression analyses were used to assess whether undergoing treatment at a high-volume facility was associated with a lower risk of overall mortality, after controlling for differences in baseline demographics, tumor presentation, and treatment characteristics. For patients undergoing surgery, multivariate regression models were used to evaluate whether patients receiving care in a high-volume facility were more likely to receive resections with limb salvage surgery than to receive amputation and whether facility volume was associated with a patient’s likelihood of having a positive or negative surgical margin.

Results
A total of 14,039 patients were included, 15% (2115) of whom underwent treatment in a high-volume facility. Patients undergoing treatment at a high-volume facility were more likely to be white, have tumors involving the pelvis, have larger tumor sizes, and have a higher tumor grade at presentation than those undergoing treatment at a low-volume facility. Unadjusted 5-year overall survival rates were greater for high-volume facilities than for low-volume facilities (65% versus 61%; p = 0.003). After controlling for differences in patient demographics, tumor characteristics (including histologic type, grade, stage, size, and location) and treatment factors, we found that patients treated at high-volume facilities had a slightly lower overall mortality risk than those treated at low-volume facilities (hazard ratio 0.85 [95% CI 0.77 to 0.93]; p < 0.001). Patients treated at high-volume facilities were also slightly more likely to undergo resection with limb-salvage surgery to than to undergo amputation (odds ratio 1.34 [95% CI 1.14 to 1.59]; p = 0.001). Patients undergoing surgical treatment at high-volume facilities also had a lower odds of having positive resection margins than those undergoing treatment at low-volume facilities (OR 0.56 [95% CI 0.44 to 0.72]; p < 0.001).

Conclusions
Patients undergoing treatment for primary malignant bone tumors at high-volume facilities experience a slightly better overall survival than those receiving treatment at low-volume facilities. Further research questioning the value of care at high-volume facilities is required before sweeping changes in regionalization can be considered.

Level of Evidence
Level III, therapeutic study.