EAU 2019: Proposal for Tripartite Reclassification of cT1 Renal Cell Carcinoma Into cT1a (very low risk), cT1b (low risk), and cT1c (intermediate risk) Substages

Barcelona, Spain (UroToday.com) According to the Guidelines, T1 renal tumors subdivision is based on the tumor size (T1a ≤4cm and T1b from 4cm to ≤7cm), but there is a mention that such sub-classification might not be optimal for nephron-sparing surgery. In this relation, new criteria are currently being investigated. A team from the University of California San Diego suggests a three-tier classification which allows more rationally risk stratification of T1 renal masses.

Authors conducted a multicenter retrospective analysis of patients with cT1 renal cell carcinoma (RCC) undergoing partial or radical nephrectomy. All patients were stratified by tumor size into three groups cT1a (≤2cm, very low risk), cT1b (2cm< and ≤5cm, low risk), and cT1c (5cm< and ≤7cm, intermediate risk). The primary outcome was recurrence-free survival (RFS) and the secondary outcome was overall survival (OS).

A total of 4710 patients were stratified into proposed T1 groups (T1a=856, T1b=2909, T1c=945; median follow-up 39 months). There was a significant difference in 5-years RFS depending on the stage (95.7%, 90.8%, and 80.8% in cT1a, cT1b and cT1c tumors, respectively [p<0.001], Figure 1a). The similar differences in 5-years OS were found (89.3%, 85.5%, and 73.3%, respectively [p=<0.001], Figure 1b).
EAU2019 Fig1a tripartite reclassification of cT1 renal cell carcinomaEAU2019 Fig1a tripartite reclassification of cT1 renal cell carcinoma

Multivariable Cox Regression analysis showed that increasing tumor stage (Referent T1a; cT1b HR=1.927 p=0.002, cT1c HR=3.687 p<0.001) was independent risk factor for RFS as well as increasing age (HR=1.02, p<0.001), diabetes mellitus (HR=1.41, p=0.017), high tumor grade (HR=2.65, p<0.001).

According to Kaplan-Meier analysis, increasing age (HR=1.05), diabetes mellitus (HR=1.57), high tumor grade (HR=1.80 (p<0.001 for all) and increasing tumor stage (Referent T1a; cT1b HR=1.10 p=0.44, cT1c HR=1.747 p<0.001) were independent risk factors for OS.

Subdivision of cT1 RCC into three clinical stage categories allows respecting the different biological potential which varies significantly. A proposed classification may influence treatment tactics and change postoperative follow-up protocols by delineating a very low risk and intermediate risk subset of renal tumors. Although a prospective observational study is needed, it is hard to carry it out because a large proportion of patients with very low-risk tumors (< 2 cm) with small tumors currently choose active surveillance, as suggested in EAU Guidelines.

Presented by: Ithaar H. Derweesh, MD, Urologic Oncologist, Professor of Urology and Radiology, the University of California San Diego, Department of Urology, San Diego, United States

Written by: Kirill Shiranov, MD, Fellow, Department of Urology, Rostov University, Rostov on Don, Russia, at the 34th European Association of Urology (EAU 2019) #EAU19 conference in Barcelona, Spain, March 15-19, 2019.