New Sarculator Prognostic Nomograms for Patients with Primary Retroperitoneal Sarcoma

To update the current Sarculator retroperitoneal sarcoma (RPS) prognostic nomograms considering the improvement in patient prognosis and the case volume effect.Survival of patients with primary RPS has been increasing over time, and the volume-outcome relationship has been well recognized. Nevertheless, the specific impact on prognostic nomograms is unknown.All consecutive adult patients with primary localized RPS treated at 8 European and North American sarcoma reference centers between 2010 and 2017 were included. Patients were divided in two groups: high volume centers (HVC, ≥13 cases/year) and low volume centers (LVC, <13 cases/year). Primary endpoints were overall survival (OS) and disease free-survival (DFS). Multivariable analyses for OS and DFS were performed. The nomograms were updated by recalibration. Nomograms performance was assessed in terms of discrimination (Harrell C index) and calibration (calibration plot).The HVC and LVC groups comprised 857 and 244 patients, respectively. Median annual primary RPS case volume (interquartile range) was 24.0 in HVC (15.0-41.3) and 9.0 in LVC (1.8-10.3). Five-year OS was 71.4% (95% CI 68.3-74.7%) in the HVC cohort and 63.3% (56.8-70.5%) in the LVC cohort (P=0.012). Case volume was associated with both OS (LVC vs. HVC HR 1.40, 95%CI 1.08-1.82, P=0.011) and DFS (HR 1.93, 95%CI 1.57-2.37, P<0.001) at multivariable analyses. When applied to the study cohorts, the Sarculator nomograms showed good discrimination (Harrell C index between 0.68 and 0.73). The recalibrated nomograms showed good calibration in the HVC group while the original nomograms showed good calibration in the LVC group.New nomograms for patients with primary RPS treated with surgery at high-volume versus low-volume sarcoma reference centers are available in the Sarculator app.