Is there a need to further subclassify pT2 renal cell cancers as implemented by the revised 7th TNM version?

BACKGROUND: The recently modified TNM classification of renal cell carcinoma (RCC) (7th edition) has implemented a subdivision of pT2 tumours into stage pT2a (>7 or ≤10 cm) versus pT2b disease (>10 cm).
OBJECTIVE: Our aim was to evaluate whether this subdivision of pT2 RCC is justified due to a clinical prognosis divergence between the two groups (pT2a vs pT2b) DESIGN, SETTING, AND PARTICIPANTS: In total, 5122 patients were subjected to either radical nephrectomy or nephron-sparing surgery at three centres in Germany (University Hospitals of Hannover, Homburg/Saar, and Marburg). Patients were reclassified into stage pT2a and pT2b according to the maximum tumour diameter as suggested by the 7th revised version of the TNM classification system. MEASUREMENTS: The t test and Fisher exact test were applied to evaluate the comparability of the two groups (pT2a vs pT2b) regarding several additional patients' and tumour-specific characteristics of known prognostic relevance for RCC. Univariable (Kaplan-Meier analysis) and multivariable statistical analyses (Cox proportional hazards regression model) were applied to identify a possible difference between the two groups (pT2a vs pT2b) regarding cancer-specific survival (CSS). RESULTS AND LIMITATIONS: Applying the new TNM classification, 579 previously pT2-staged patients were divided into 445 (76.9%) with pT2a and 134 (23.1%) with pT2b tumours. Kaplan-Meier curves revealed no significant difference in CSS between pT2a and pT2b patients; 5-yr CSS was 79.0% and 74.1%, respectively (p=0.38). When applying multivariable analysis, unlike tumour grade and N/M status, pT2 subclassification failed to independently predict survival in RCC patients.
CONCLUSIONS: The new subclassification of pT2 RCC into two different subgroups as suggested by the latest modification of the TNM system does not yield additional/prognostic information.