Preoperative metastatic disease burden to predict overall survival following cytoreductive nephrectomy independent of IMDC risk category.

Abstract

652 Background: Studies suggest that overall survival (OS) following cytoreductive nephrectomy (CN) is associated with preoperative tumor measurements including primary tumor diameter, number of metastatic sites, sum of metastatic tumor diameters and primary tumor percent of overall burden. Current risk models, however, do not account for tumor burden. This study evaluated associations between OS and preoperative tumor measurements for patients treated with CN during the targeted therapy era. Methods: Data for consecutive mRCC patients treated with CN at 4 institutions from 2006-2017 were analyzed after determining IMDC risk category, primary tumor (PT) diameter, number of metastatic sites, sum of metastatic tumor diameters and PT percentage of overall burden. Univariate and multivariable (MV) Cox models evaluated tumor measurement and IMDC risk associations with OS. Results: A total of 617 patients were available for analysis. Median PT diameter was 10.0 cm (IQR 7-13cm), number of metastatic sites was 2 (IQR 1-2), sum of metastatic tumor diameters was 4.5 cm (IQR 2-10cm) and PT percent of overall burden was 73.7% (IQR 60-85%). After univariate analysis, all 4 tumor burden measures were associated with OS (p≤0.001 for all). MV models evaluating IMDC risk category with individual tumor burden measurements demonstrated that all measures were predictive as continuous variables: PT diameter (HR 1.03, 95% CI 1.01-1.06, p=0.007), sum of metastatic tumor diameters (HR 1.04, 95% CI 1.02-1.05, p<0.001), PT percent of overall burden (HR 0.43, 95% CI 0.27-0.68, p<0.001), and number of metastatic sites (HR 1.52, 95% CI 1.25-1.85, p<0.001). Additional MV models were created using clinically significant tumor measurement cutoffs and IMDC risk groups. OS was independently associated with IMDC intermediate (HR 3.17, 95% CI 1.84-5.44, p<0.001) and poor risk (HR 3.85, 95% CI 2.21-6.70, p<0.001), PT percentage of overall burden <90% (HR 1.41, 95% CI 1.05-1.89, p=0.021), and >2 metastatic sites (HR 1.60, 95% CI 1.29-2.00, p<0.001). Conclusions: PT and metastatic disease burden are independently associated with OS following CN. Future risk models should include tumor burden measurements.