Cancer-specific mortality free survival rates in non-metastatic non-clear cell renal carcinoma patients at intermediate/high risk of recurrence

BACKGROUND: To date, five trials testing the effect of adjuvant systemic therapy in surgically treated non-metastatic renal cell carcinoma included patients with non-clear cell histology. We tested the effect of papillary vs. chromophobe histological subtype, stage, and grade on 10-year cancer-specific survival, in patients eligible for & GE;1 such trial.METHODS: We identified patients meeting ASSURE, SORCE, EVEREST, PROSPER, or RAMPART trial inclusion criteria in the SEER (2000-2018) database. Kaplan-Meier analyses estimated 10-year survival rates and multivariable Cox regression models tested for the independent predictor status of histological subtype, stage, and grade.RESULTS: We identified 5465 (68%) papillary and 2562 (32%) chromophobe renal cell carcinoma patients. Cancer -specific survival rates at 10 years were 77% in papillary vs. 90% in chromophobe. In multivariable Cox regression models applied to papillary patients, cancer-specific mortality independent predictor status was reached for T3G3-4 (HR 2.9), T4Gany (HR 3.4), TanyN1G1-2 (HR 3.1), and TanyN1G3-4 (HR 8.0, P<0.001), relative to T1/2Gany. In multivariable Cox regression models applied to chromophobe patients, mortality independent predictor status was reached for T3G3-4 (HR 3.6), T4Gany (HR 14.0), TanyN1G1-2 (HR 5.7), and TanyN1G3-4 (HR 15.0, P<0.001), relative to T1/2Gany.CONCLUSIONS: In surgically treated non-metastatic intermediate/high-risk renal cell carcinoma patients, papillary histologic subtype exhibited worse cancer-specific survival than chromophobe histologic subtype. Although stage and grade represented independent predictors in both histological subtype groups, the magnitude of their effect was invari-ably worse in chromophobe than in papillary patients. In consequence, papillary and chromophobe patients should be considered separate entities instead of being combined under the non-clear cell designation.