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BACKGROUND: RENAL Nephrometry Score (RENAL NS) and C-Index quantify the anatomic features of renal tumors for patients undergoing partial nephrectomy (PN). Here, we compare C-Index and RENAL NS to predict the complexity of PN using a composite complexity endpoint (CCE).
METHODS: A binary CCE of PN was determined a priori and defined as ≥1 of the following: positive surgical margin, estimated blood loss >1 standard deviation above mean, urine leak, any ≥Clavien Grade 3 complication, and new ≥ Stage 3 chronic kidney disease (eGFR<60mL/min/1.73m). Data were retrospectively obtained for patients who had PN at one institution from 2007-2009. Blinded physicians reviewed preoperative imaging and assigned RENAL NS and C-Index. Univariate logistic regression analysis was used for associations between scoring systems and the CCE. Area under receiver operating characteristic curve (AUC) was calculated for C-Index and RENAL NS.
RESULTS: Among 212 patients, mean C-Index was 2.8±1.7 and RENAL NS was 7.5±1.8. 85 patients (40.1%) met the CCE. Both C-Index and RENAL NS were significantly associated with the CCE (p<0.01). With each additional Nephrometry point, the odds of meeting the CCE increased 1.37 times (p<0.01). With each additional C-Index unit, the odds of meeting the CCE decreased 0.70 times (p<0.01). The AUC for RENAL NS and C-Index were 0.66 (95%CI: 0.58-0.73) and 0.69 (95%CI: 0.61-0.76), respectively (p=0.33).
CONCLUSIONS: As measured by CCE, C-Index and RENAL NS have highly significant association with complexity of PN, with similar predictive abilities. Adoption of one system over another thus may be determined by their relative ease and speed of calculation.