Preoperative predictors of malignancy and unfavorable pathology for clinical T1a tumors treated with partial nephrectomy: A multi-institutional analysis

Purpose: To determine preoperative predictors associated with renal cell carcinoma (RCC) and unfavorable pathology in small renal masses treated with partial nephrectomy (PN). Materials and methods: PN records from 5 centers were retrospectively queried for patients with a clinically localized single tumor <4. cm on imaging (clinical T1a). Between 2007 and 2013, 1,009 patients met the inclusion criteria. Unfavorable pathology was defined as any grade III or IV RCC or tumors upstaged to pathologic T3a disease. Logistic regression models were used to determine preoperative characteristics associated with RCC and with unfavorable pathology. Results: A total of 771 (76.4%) patients were found to have RCC and 198 (19.6%) had unfavorable pathology. On multivariate, bootstrap-adjusted logistic regression analysis, factors associated with the presence of malignancy were imaging tumor size≥3. cm (odds ratio [OR] = 1.46; P = 0.040), male sex (OR = 1.88; P<0.0001), and nephrometry score≥8 (OR = 1.64; P = 0.005). These same factors were independently associated with risk of unfavorable pathology: size≥3. cm (OR = 1.46; P = 0.021), male sex (OR = 2.35; P<0.0001), and nephrometry score≥8 (OR = 1.49; P = 0.015). The c statistic was 0.62 for the predicting malignancy and 0.63 for unfavorable pathology. Conclusions: In this multi-institutional cohort, male sex, imaging tumor size≥3. cm, and nephrometry score≥8 were predictors of RCC and adverse pathology following PN. These factors may assist in risk stratification and selective renal mass biopsy before decision making. Further studies are necessary to validate these findings.