Sarcomatoid Dedifferentiation as a Predictor of Cancer-Specific Mortality in Surgically Treated Localized Renal Cell Carcinoma

Background: In contemporary surgically treated patients with localized high-grade (G3 or G4) clear-cell renal cell carcinoma (ccRCC), it is not known whether presence of sarcomatoid dedifferentiation is an independent predictor and/or an effect modifier, when cancer-specific mortality (CSM) represents an endpoint. Methods: Within the Surveillance, Epidemiology, and End Results database, all surgically treated localized high-grade ccRCC patients treated between 2010 and 2020 were identified. Univariable and multivariable Cox-regression models were used. Results: In 18,853 surgically treated localized high-grade (G3 or G4) ccRCC patients, 5-year CSM-free survival was 87% (62% vs. 88% with vs. without sarcomatoid dedifferentiation, p < 0.001). Presence of sarcomatoid dedifferentiation was an independent predictor of higher CSM (hazard ratio [HR] 1.8, p < 0.001). In univariable survival analyses predicting CSM, presence versus absence of sarcomatoid dedifferentiation in G3 versus G4 yielded the following hazard ratios: HR 1.0 in absent sarcomatoid dedifferentiation in G3; HR 2.7 (p < 0.001) in absent sarcomatoid dedifferentiation in G4; HR 3.9 (p < 0.001) in present sarcomatoid dedifferentiation in G3; HR 5.1 (p < 0.001) in present sarcomatoid dedifferentiation in G4. Finally, in multivariable Cox-regression analyses, the interaction terms defining present versus absent sarcomatoid dedifferentiation in G3 versus G4 represented independent predictors of higher CSM. Conclusions: In contemporary surgically treated patients with localized high-grade ccRCC, sarcomatoid dedifferentiation is not only an independent multivariable predictor of higher CSM, but also interacts with tumor grade and results in even better ability to predict CSM.