Few data factually support the prognostic distinction between renal cell carcinomas (RCC) < 2 vs. 2.1-4 cm, in terms of cancer-specific mortality (CSM). We investigated CSM rates over time in <2 vs. 2.1-4 cm RCC, according to patient and tumor characteristics.
Within the Surveillance, Epidemiology and End Results (SEER) database, we focused on patients with TNM RCC who underwent either radical or partial nephrectomy between 2000 and 2015. Temporal trends, Kaplan-Meier plots and multivariable Cox-regression analyses assessed CSM.
Of 43,147 TNM patients, 12,238 (28.4%) harbored RCC < 2 cm and 30,909 (71.6%) 2.1-4 cm RCC. The distribution of histological subtypes according to 2 cm cut-off was as follows: a). clear-cell G1/G2: 64.5 vs. 61.8%; b). papillary G1/G2 15.9 vs. 11.1%; c). clear-cell G3/G4: 9.9 vs. 16.1%; d). papillary G3/G4 4.9 vs. 5.4%; and e). chromophobe 4.9 vs. 5.2%. Five-year CSM rates were invariably lower in RCC < 2 cm than in 2.1-4 cm, for all histological subtypes and grade groups (a-e), even after additional multivariable adjustment for age and residual tumor size differences. 5-year CSM rates improved in more contemporary years, in both tumor size groups (< 2 vs. 2.1-4 cm), but to a greater extent in 2.1-4 cm renal masses.
Our results validate the presence of prognostically more favorable CSM outcomes in RCC < 2 cm vs. 2.1-4 cm, across all histological subtypes and grades. Moreover, temporal improvements were also recorded in both <2 and 2.1-4 cm RCC groups, with more pronounced improvements in patients with 2.1-4 cm renal masses. However, prospective randomized trials are needed to further confirm our results.

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