Survival and progression in high grade tumour subset of G2 and G3 pT1 bladder transitional cell carcinoma

International Society of Urological Pathology (ISUP) Consensus Conference on Current Issues in Bladder Cancer. Working Group 2: Grading of Mixed Grade, Invasive Urothelial Carcinoma Including Histologic Subtypes and Divergent Differentiations, and Non-Urothelial Carcinomas

The 2022 International Society of Urological Pathology (ISUP) Consensus Conference on Urinary Bladder Cancer Working Group 2 was tasked to provide evidence-based proposals on the applications of grading in noninvasive urothelial carcinoma with mixed grades, invasive urothelial carcinoma including subtypes (variants) and divergent differentiations, and in pure non-urothelial carcinomas. Studies suggested that predominantly low-grade noninvasive papillary urothelial carcinoma with focal high-grade component has intermediate outcome between low- and high-grade tumors. However, no consensus was reached on how to define a focal high-grade component. By 2004 WHO grading, the vast majority of lamina propria-invasive (T1) urothelial carcinomas are high-grade, and the rare invasive low-grade tumors show only limited superficial invasion. While by 1973 WHO grading, the vast majority of T1 urothelial carcinomas are G2 and G3 and show significant differences in outcome based on tumor grade. No consensus was reached if T1 tumors should be graded either by the 2004 WHO system or by the 1973 WHO system. Because of the concern for underdiagnosis and underreporting with potential undertreatment, participants unanimously recommended that the presence of urothelial carcinoma subtypes and divergent differentiations should be reported. There was consensus that the extent of these subtypes and divergent differentiations should also be documented in biopsy, transurethral resection, and cystectomy specimens. Any distinct subtype and divergent differentiation should be diagnosed without a threshold cutoff, and each type should be enumerated in tumors with combined morphologies. The participants agreed that all subtypes and divergent differentiations should be considered high-grade according to the 2004 WHO grading system. However, participants strongly acknowledged that subtypes and divergent differentiations should not be considered as a homogenous group in terms of behavior. Thus, future studies should focus on individual subtypes and divergent differentiations rather than lumping these different entities into a single clinicopathological group. Likewise, clinical recommendations should pay attention to the potential heterogeneity of subtypes and divergent differentiations in terms of behavior and response to therapy. There was consensus that invasive pure squamous cell carcinoma and pure adenocarcinoma of the bladder should be graded according to the degree of differentiation. In conclusion, this summary of the International Society of Urological Pathology Working Group 2 proceedings addresses some of the issues on grading beyond its traditional application, including for papillary urothelial carcinomas with mixed grades and with invasive components. Reporting of subtypes and divergent differentiation is also addressed in detail, acknowledging their role in risk stratification. This report could serve as a guide for best practices and may advise future research and proposals on the prognostication of these tumors.

The impact of grading scheme on non-muscle invasive bladder cancer progression: potential utility of hybrid grading schemes

Non-muscle invasive bladder cancer (NMIBC) grade is a major determinant of progression risk. The most widely utilised grading systems are the World Health Organization (WHO) 1973 and 2004 schemes. Recent publications suggest the utility of combining both into a four-tier or a hybrid three-tier system, subdividing WHO 2004 high grade into two separate categories while maintaining low grade as a single group. We identified two retrospective cohorts of bladder resections/biopsies of papillary urothelial NMIBC with long term clinical follow-up. The sentinel specimen was assessed for WHO 2004 and 1973 grade, along with pathological stage and carcinoma in situ. Each case was additionally stratified into a hybrid three-tier system (low grade; high grade, grades 2 and 3) and a four-tier system (low grade, grades 1 and 2; high grade, grades 2 and 3). Uni- and multivariable analysis for progression and event free survival (PFS/EFS) were calculated along with the time dependent area under the curve (AUC) for each grading scheme. There were 609 cases (Cohort A, n=343; Cohort B, n=266), including 449 (74%) pTa, 156 pT1 (26%) and four pTx with 338 (56%) low grade (177, grade 1; 161, grade 2) and 271 (44%) high grade (137, grade 2; 134, grade 3). A total of 108 patients progressed (17.7%): 97 high grade, (grade 3, n=59; grade 2, n=38). Multivariable analyses of PFS with the hybrid 3- and 4-tier systems showed higher Harrell's concordance indices (0.851 and 0.853, respectively) than WHO 1973 (0.844) and WHO 2004 (0.846). In both cohorts AUC values were higher (0.77-0.85) for the two hybrid grading systems compared to WHO 1973 or WHO 2004 (0.72-0.82). Similar results were seen on analysis of EFS. The data support the use of a hybrid three-tier or four-tier grading system to improve stratification of NMIBC patients.

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

BACKGROUND

In the current European Association of Urology (EAU) non-muscle-invasive bladder cancer (NMIBC) guideline, two classification systems for grade are advocated: WHO1973 and WHO2004/2016.

OBJECTIVE

To compare the prognostic value of these WHO systems.

DESIGN, SETTING, AND PARTICIPANTS

Individual patient data for 5145 primary Ta/T1 NMIBC patients from 17 centers were collected between 1990 and 2019. The median follow-up was 3.9 yr.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Univariate and multivariable analyses of WHO1973 and WHO2004/2016 stratified by center were performed for time to recurrence, progression (primary endpoint), cystectomy, and duration of survival, taking into account age, concomitant carcinoma in situ, gender, multiplicity, tumor size, initial treatment, and tumor stage. Harrell's concordance (C-index) was used for prognostic accuracy of classification systems.

RESULTS AND LIMITATIONS

The median age was 68 yr; 3292 (64%) patients had Ta tumors. Neither classification system was prognostic for recurrence. For a four-tier combination of both WHO systems, progression at 5-yr follow-up was 1.4% in low-grade (LG)/G1, 3.8% in LG/G2, 7.7% in high grade (HG)/G2, and 18.8% in HG/G3 (log-rank, p < 0.001). In multivariable analyses with WHO1973 and WHO2004/2016 as independent variables, WHO1973 was a significant prognosticator of progression (p <  0.001), whereas WHO2004/2016 was not anymore (p =  0.067). C-indices for WHO1973, WHO2004, and the WHO systems combined for progression were 0.71, 0.67, and 0.73, respectively. Prognostic analyses for cystectomy and survival showed results similar to those for progression.

CONCLUSIONS

In this large prognostic factor study, both classification systems were prognostic for progression but not for recurrence. For progression, the prognostic value of WHO1973 was higher than that of WHO 2004/2016. The four-tier combination (LG/G1, LG/G2, HG/G2, and HG/G3) of both WHO systems proved to be superior, as it divides G2 patients into two subgroups (LG and HG) with different prognoses. Hence, the current EAU-NMIBC guideline recommendation to use both WHO classification systems remains correct.

PATIENT SUMMARY

At present, two classification systems are used in parallel to grade non-muscle-invasive bladder tumors. Our data on a large number of patients showed that the older classification system (WHO1973) performed better in terms of assessing progression than the more recent (WHO2004/2016) one. Nevertheless, we conclude that the current guideline recommendation for the use of both classification systems remains correct, since this has the advantage of dividing the large group of WHO1973 G2 patients into two subgroups (low and high grade) with different prognoses.

Survival Following the Diagnosis of Noninvasive Bladder Cancer: WHO/International Society of Urological Pathology Versus WHO Classification Systems

PURPOSE

The WHO/International Society of Urological Pathology classification of bladder cancer, introduced in 1998, differs from the traditional 1973 WHO classification. Few studies have reported survival data based on the WHO/International Society of Urological Pathology classification and none has demonstrated clear superiority compared to the 1973 WHO system. In a large, nonselected population of patients with bladder cancer we rated all incident tumors using each system and compared long-term patient survival.

MATERIALS AND METHODS

New Hampshire residents with bladder cancer diagnosed between 1994 and 2000 were identified through the State Cancer Registry. Slides were retrieved from more than 90% of cases and reviewed by a single pathologist. Tumors were classified according to WHO and WHO/International Society of Urological Pathology criteria. Overall patient survival was determined for the cohort of 504 patients after an average of 7 years using a national mortality database.

RESULTS

For both grading systems there was a gradient of progressively lower survival times from the lowest grade to the highest grade tumors. Hazard ratios and 95% confidence intervals for the WHO/International Society of Urological Pathology system were 1.9 (1.0-3.4) for low grade papillary urothelial carcinoma and 3.0 (1.5-6.0) for high grade papillary urothelial carcinoma, compared to papillary urothelial neoplasms of low malignant potential. For the WHO (1973) system compared to grade 1 tumors the hazard ratio for grade 2 tumors was 1.8 (1.1-3.1) and for grade 3 was 2.4 (1.2-4.7).

CONCLUSIONS

Advantages of the WHO/International Society of Urological Pathology bladder tumor classification include more detailed diagnostic criteria, the ability to define a lesion with minimal malignant potential and the ability to identify a larger group of patients needing closer surveillance. However, we found that the WHO/International Society of Urological Pathology tumor categories did not detect a clear overall survival advantage compared to the WHO (1973) classification system.