Identifying the Minimum Volume Threshold for Retroperitoneal Soft Tissue Sarcoma Resection: Merging National Data with Consensus Expert Opinion

Abstract

The complexity of retroperitoneal soft tissue sarcoma (RPS) surgery has prompted international recommendations to regionalize it to high-volume hospitals (HVHs). A minimum procedural volume threshold for RPS is not yet defined, hampering effective referral and regionalization in the US. This multihospital study sought to establish an HVH threshold informed by national data and international expert opinion. The 2004-2015 National Cancer Database identified 8,721 surgically treated RPS patients. Multivariable models, using linear splines, identified annual volume thresholds predictive of overall and 90-day mortality. Transatlantic Australasian Retroperitoneal Soft Tissue Sarcoma Working Group members (n= 48) completed a 15-item survey regarding these data. Overall mortality risk was reduced by 4% per additional case (hazard ratio [HR] 0.96, 95% CI 0.95 to 0.98) up to a threshold of 13 cases/year; no further reduction was observed over 13 (HR 0.99, 95% CI 0.97 to 1.01). After revealing the results from our statistical analysis, 71.4% of respondents who initially chose >30 cases/year as a cutoff shifted their response to a lower value. More than 56% cited 11 to 20 procedures/year as the cutoff for an HVH. Median survival in hospitals with <13 vs >13 cases/year was 94 vs 139 months, respectively (p < 0.001). Forty percent of respondents cited 1% to 2% as an acceptable90-day mortality. This was achieved with a minimum of 13 cases/year based on risk-adjusted survival analysis. This is the first multicenter analysis to merge data-driven RPS surgery volume thresholds to clinically meaningful sarcoma expert opinions. These findings will help inform national/international consensus recommendations, a practical volume threshold, trial design, and motivate evidence-based hospital referral.