The WHO classification of 1973 is more suitable than the WHO classification of 2004 for predicting survival in pT1 urothelial bladder cancer

What's known on the subject? and What does the study add? Grading so far is the most important prognostic parameter in non muscle-invasive urothelial bladder cancer. We first compared prognostic value of grading concerning WHO classifications 1973 and 2004 on stage T1 bladder cancer. OBJECTIVE To ascertain which of the currently defined World Health Organization (WHO) grading classifications of pT1 urothelial bladder cancer (BC), published in 1973 and 2004, is more suitable for predicting outcome. PATIENTS AND METHODS Transurethral resection of the bladder (TURB) specimens of 310 patients with first diagnosis of initial pT1 BC were reassessed by three urological pathologists according to the WHO classifications of 1973 and 2004. The TURB procedure was followed by either immediate cystectomy or adjuvant bacille Calmette-Guerin (BCG) instillations. Kaplan-Meier analysis was used to compare survival rates of the different tumour grades (mean follow-up was 57 months). RESULTS According to the 1973 WHO classification, none of the pT1 BC specimens were graded as G1, while 36% were graded as G2 and 64% were graded as G3. Histological reassessment according to the 2004 WHO classification highlighted only 4% low-grade and 96% high-grade tumours. The 10-year cancer-specific survival rates of high-grade tumours (85%) were intermediate between G2 (96%) and G3 (78%). CONCLUSIONS The results of the present study support the presumption that the 1973 WHO classification is more suitable for predicting outcome for pT1 tumours, by defining at least two prognostic groups. A new classification should revise the definition of low- and high-grade pT1 BC to preserve the prognostic value of tumour grading.