Prognostic performance of the 1973 and 2004 WHO grading classification in upper tract urothelial carcinoma

Grading of upper tract urothelial carcinoma (UTUC) is routinely used in clinical practice; however, reports concerning prognostic performance of different grading systems are contradictory. We aim to assess the clinical reliability of the 1973 and 2004 World Health Organization (WHO) grading classification systems in UTUC.

We retrospectively evaluated 458 consecutive patients with UTUC from 2008 to 2013. The postoperative tumor grades were evaluated by a single uropathologist using the 1973 and 2004 WHO grade classification systems. The Kaplan-Meier method was used to estimate cancer-specific survival (CSS) and overall survival (OS). Univariate and multivariate analyses were used to test the association between clinical variables and the CSS and OS rates.

There were 133 (29.0%) low-grade patients and 325 (71.0%) high-grade patients. The 3-year CSS rates were 87.0% and 76.0% for G2 and G3 disease and 89.0% and 80.0% for low- and high-grade disease according to the 2004 system, respectively. For all UTUC patients, there were significant differences in the CSS and OS rates between G2 and G3 cases, as well as between the low- and high-grade groups. The CSS and OS rates were significantly different between the G2 and G3 cases for the overall high-grade population (CSS: P = 0.003; OS: P = 0.009), while no significant difference emerged between low- and high-grade tumors in G2 UTUC patients (CSS: P = 0.717; OS: P = 0.280). In the subgroup of high-grade non-muscle-invasive tumors, the 1973 WHO grading system was an independent predictor of CSS (P = 0.045).

The results support the hypothesis that the 1973 WHO system is superior to the 2004 system for predicting clinical outcomes in patients with non-muscle-invasive UTUC.