Usefulness of a Pretreatment CT-Based Modified RENAL Nephrometry Score in Predicting Renal Function After Cryotherapy for T1a Renal Mass

Purpose We investigated the usefulness of the modified RENAL nephrometry (mRN) scoring system for predicting post-cryotherapy renal function in patients with T1a renal mass. Patients and Methods A total of 75 patients with a T1a renal mass were enrolled. The mRN score was determined based on the tumor size, the tumor's exophytic/endophytic properties, the tumor's nearness to the collecting system, and the anterior/posterior location of the kidney. The change in the estimated glomerular filtration rate (eGFR) was calculated as follows: Delta eGFR=100 x ([pretreatment eGFR - eGFR at 6 months after cryotherapy]/pretreatment eGFR). Based on the Delta eGFR results, we classified the patients into two groups: a preserved renal function group (Delta eGFR < 10%) and an impaired renal function group (Delta eGFR >= 10%). We then analyzed the relationships between the mRN score and Delta eGFR and between the mRN score and the chronic kidney disease (CKD) stage. Results The mean Delta eGFR for all patients was 5.5%. The mRN scores of the preserved renal function group (5.8 +/- 0.3) were significantly lower than those of the impaired group (7.4 +/- 0.3) (p < 0.001). When the mRN score cutoff value was set at 7 points, the mRN had 67.7% sensitivity, 72.7% specificity, 61.8% positive predictive value (PPV), 76.1% negative predictive value (NPV), and 70.7% accuracy for predicting impaired renal function. For predicting a deterioration of CKD stage, the mRN had 92.9% sensitivity, 67.2% specificity, 39.4% PPV, 97.6% NPV, and 72% accuracy. Conclusion Our newly proposed modified RENAL nephrometry score was suggested to be useful for predicting renal function after renal cryotherapy.