To evaluate whether incidental pathologic T3a (pT3a) upstaging after partial nephrectomy (PN) for clinical T1 disease results in inferior oncologic outcomes compared to pT1a-b disease.

Retrospective chart review was completed at the University of Michigan and Moffitt Cancer Center to identify patients undergoing PN for clinical T1 masses between 1995 and 2015. A total of 1955 patients were identified, of which 95 had pT3a upstaging. Median follow-up was 38.2 months. Patients with pT3a disease were individually matched by clinicopathologic features with patients undergoing PN with pT1a-b disease in a 1:2 ratio. Kaplan-Meier analysis and univariate and multivariable Cox proportional hazards regression analysis were performed. Primary endpoint was recurrence-free survival (RFS). Secondary endpoints were all-cause mortality, cancer-specific survival (CSS), and rates of local and distant recurrence.

Recurrence rates were significantly higher in pT3a disease compared to pT1a-b controls (P <.01). In those patients with pT3a upstaging, 3- and 5-year RFS were 81% and 58%, compared to 86% and 75% in pT1a-b controls (P = .01). CSS at 3 and 5 years were 91% and 90% in pT3a disease and 100% and 97% in pT1a-b controls (P <.01). All-cause mortality at 3 and 5 years were 82% and 71% in pT3a disease and 93% and 80% in pT1a-b controls (P = .04). Univariate and multivariable analysis of pT3a disease demonstrated no association between demographic or pathologic characteristics and RCC recurrence.

Patients with pT3a upstaging following PN experience a significantly reduced RFS and CSS when compared to pT1 disease.