Renal tumour invasion index as a novel anatomical classification predicting urological complications after partial nephrectomy

Abstract

Objective. The goal of anatomical classification systems (ACSs) is to assess renal tumour complexity and predict surgical complications. However, the present ACSs may include some relatively unimportant components and may be complicated to use. This study introduces the invasion depth of the renal tumour divided by the parenchymal thickness, called the renal tumour invasion index (RTII), as a novel ACS and compares it with previous ACSs in predicting urological complications after partial nephrectomy. Material and methods. This retrospective single-institution study assessed 280 consecutive patients subjected to a planned partial nephrectomy. The main outcome was perioperative 30-day urological complications. RTII was compared with the PADUA (preoperative aspects and dimensions used for an anatomical) classification score, RENAL (radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior and location relative to polar lines) nephrometry score and C (centrality) index to predict urological complications, using statistical methods of receiver operating curve and logistic binary regression. Results. Areas under the curve for RTII, RENAL, C index and PADUA were 0.64 (95% CI 0.57–0.72, p < 0.001), 0.61 (95% CI 0.54–0.69, p = 0.004), 0.64 (95% CI 0.57–0.71, p < 0.001) and 0.57 (95% CI 0.49–0.65, p = 0.06), respectively, indicating that all the ACSs studied are able to predict urological complications. Similarly, in a multivariate logistic regression model adjusted for comorbidity and surgical approach, all ACSs were statistically significant predictors of urological complications. Conclusions. RTII is as good as the previous more complicated ACSs in predicting urological complications after partial nephrectomy. As a simple measurement with a straightforward anatomical interpretation, RTII may be useful in counselling patients and stratifying patients in studies.

Key Words::

• anatomical classification
• complications
• partial nephrectomy
• renal cell carcinoma

Acknowledgements

We thank MSocSc Jessica Nisen for her statistical support. The study was supported by an EVO grant from Helsinki University Central Hospital.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.