Combining two grading systems: the clinical validity and inter-observer variability of the 1973 and 2004 WHO bladder cancer classification systems assessed in a UK cohort with 15 years of prospective follow-up

Abstract

Purpose Paucity of reliable long-term data on the prognostic implications of the 2004 WHO bladder cancer classification system necessitates utilisation of both this and the 1973 grading systems. This study evaluated, in noninvasive (pTa) bladder tumours, the prognostic value of the 2004 system independently and in combination with the 1973 system while establishing concordance between tertiary centre uropathologists. Methods We used a cohort of non-muscle invasive bladder cancer (NMIBC) patients diagnosed between 1991 and 93 where tumour features were gathered prospectively with detailed cystoscopic follow-up data recorded over 15 years. Initial grading was by one senior expert uropathologist (UP1) using the 1973 WHO classification alone. Subsequently, two other expert uropathologists (UP2 and UP3), blinded to the previous grading, re-evaluated the pathology slides and graded the tumours using both the 1973 and 2004 systems. Association between grade and recurrence/progression was analysed and the Cohen Kappa test assessed concordance between pathologists. Results Of 370 new NMIBC, 229 were staged noninvasive (pTa). Recurrence rates were 46.2% and 50.0% for LGPUC (low-grade papillary urothelial carcinoma) and HGPUC (high-grade papillary urothelial carcinoma), respectively, while progression was seen in 3.9% and 10.0% of LGPUC and HGPUC, respectively. Concordance between uropathologists UP2 and UP3 for the 2004 and 1973 systems was good (Kappa = 0.69) and fair (Kappa = 0.25), respectively. Conclusions With good inter-observer concordance, the 2004 WHO classification system of noninvasive bladder tumours appears to accurately predict recurrence and progression risks. The combination of both grading systems to low-grade tumours allows further refinement of the natural history.

Meta-analysis of global variations in grade of pT1 urothelial bladder cancer and supplementary evaluation of a Sri Lankan cohort

“…[3] A single-institution study from the UK on TURBT or biopsy specimens showed that reproducibility of grading utilizing the 2004 system was 'good' (Kappa = 0.69) and for the 1973 system to be 'fair' (Kappa = 0.25). [61] Tosoni et al found that in a single-institution series of TURBT specimens, there was a discrepancy in the grading of 38% of patients evaluated by two uropathologists. [62] In a singleinstitution USA study of TURBT specimens, reassessment of histopathology by dedicated uropathologists showed a change in the original diagnosis in 27% including a change in grade in 5%; this implied a potential change in treatment in 15% of patients.…”

Re: Bas W.G. van Rhijn, Anouk E. Hentschel, Johannes Bründl, et al. Prognostic Value of the WHO1973 and WHO2004/2016 Classification Systems for Grade in Primary Ta/T1 Non–muscle-invasive Bladder Cancer: A Multicenter European Association of Urology Non–muscle-invasive Bladder Cancer Guidelines Panel Study. Eur Urol Oncol 2021;4:182–91

“…In conclusion, it is undeniable that both the 1973 and 2004/2016 WHO grading systems have their own clinical significance [1] and the "combination of both grading systems to low-grade tumors allows further refinement of the natural history" [9]. However, we feel that the background of the systems should be readdressed in order to reach the goal of a single successful grading system, Fig.…”

What's new in WHO fifth edition – urinary tract

“…The distinction of low‐grade (LG) and high‐grade (HG) carcinomas reflects the known genetic alterations in bladder carcinogenesis and allows for greater harmonisation with the terminology and clinical implications of urinary cytology findings. Furthermore, for this classification, a diagnostic term that should be used has better reproducibility and interobserver variability than the former 1973 grading scheme (G1–G3) 7,8 . The descriptions and images in the fifth edition (as in former editions) are provided to offer a reference and instructions to reproduce the LG/HG distinction.…”