Renal lesions with low R.E.N.A.L nephrometry score are associated with more indolent renal cell carcinomas (RCCs) or benign histology: findings in an Australian cohort.

OBJECTIVE: To validate the relationship of the R.E.N.A.L nephrometry score to histological features of renal lesions treated by surgical excision by radical nephrectomy (RN) or nephron-sparing surgery (NSS) at an Australian tertiary referral centre. PATIENTS AND METHODS: Patients undergoing surgery between 2005 and 2009 with imaging studies available were included. The R.E.N.A.L. nephrometry score is an objective measure of factors important in determining suitability for NSS, e.g. size, exophytic nature, proximity to collecting system and polar location, and R.E.N.A.L scoring was done using the online template at http://www.nephrometry.com. Pathological details were collected by retrospective chart review. Comparisons were made using chi-squared or Fisher's exact tests and trends analysed by linear regression.
RESULTS: The rate of benign pathology decreased from 12/58 (20.7%) low-complexity lesions to 1/16 (6.2%) high-complexity lesions (P= 0.09), renal cell carcinomas (RCCs) were stable between 45/58 (77.6%) and 13/16 (81.2%), but other malignancies increased (P= 0.058) from 1/58 (1.7%) to 2/16 (12.5%). Among the RCCs, high vs low R.E.N.A.L score was associated with an increasing risk of clear cell histology (84.6% vs 64.4%, P < 0.05), stage ≥ pT3 (76.9% vs 8.9%, P < 0.001) and grade 4 tumours (15.4% vs 2.2%, P < 0.05), and conversely with a lower risk of papillary histology (0% vs 24.4%, P < 0.02) and stage T1a (0% vs 84.4%, P < 0.001).
CONCLUSIONS: Increasing R.E.N.A.L score is associated with histological features of tumour aggressiveness, thus reinforcing the need for RN for lesions with a high score, and conversely the safety of NSS or observation for lesions with a low score.