International Society of Urological Pathology Consensus Conference on Current Issues in Bladder Cancer. Working Group 4: Molecular Subtypes of Bladder Cancer-Principles of Classification and Emerging Clinical Utility.

Molecular subtyping has been a major focus of bladder cancer research over the past decade. Despite many promising associations with clinical outcomes and treatment response, its clinical impact has yet to be defined. As part of the 2022 International Society of Urological Pathology Conference on Bladder Cancer, we reviewed the current state of the science for bladder cancer molecular subtyping. Our review included several different subtyping systems. We derived the following 7 principles, which summarize progress and challenges of molecular subtyping: (1) bladder cancer has 3 major molecular subtypes: luminal, basal-squamous, and neuroendocrine; (2) signatures of the tumor microenvironment differ greatly among bladder cancers, particularly among luminal tumors; (3) luminal bladder cancers are biologically diverse, and much of this diversity results from differences in features unrelated to the tumor microenvironment, such as FGFR3 signaling and RB1 inactivation; (4) molecular subtype of bladder cancer associates with tumor stage and histomorphology; (5) many subtyping systems include idiosyncrasies, such as subtypes recognized by no other system; (6) there are broad fuzzy borders between molecular subtypes, and cases that fall on these fuzzy borders are often classified differently by different subtyping systems; and (7) when there are histomorphologically distinct regions within a single tumor, the molecular subtypes of these regions are often discordant. We reviewed several use cases for molecular subtyping, highlighting their promise as clinical biomarkers. Finally, we conclude that data are currently insufficient to support the routine use of molecular subtyping to guide bladder cancer management, an opinion shared with the majority of conference attendees. We also conclude that molecular subtype should not be considered an "intrinsic" property of a tumor but should instead be considered the result of a specific laboratory test, performed using a specific testing platform and classification algorithm, validated for a specific clinical application.

Report From the International Society of Urological Pathology (ISUP) Consultation Conference On Molecular Pathology Of Urogenital Cancers. II. Molecular Pathology of Bladder Cancer: Progress and Challenges.

During the 2019 International Society of Urological Pathology Consultation Conference on Molecular Pathology of Urogenital Cancer, the Working Group on Bladder Cancer presented the current status and made recommendations on the diagnostic use of molecular pathology, incorporating a premeeting survey. Bladder cancers are biologically diverse and can be separated into "molecular subtypes," based on expression profiling. These subtypes associate with clinical behavior, histology, and molecular alterations, though their clinical utility has not been demonstrated at present and use in bladder cancer is not recommended. Mutations in the TERT promoter are present in the majority of bladder cancers, including the noninvasive stage of tumor evolution, but not in reactive conditions. Mutational analysis of the TERT promoter thus distinguishes histologically deceptive cancers from their benign mimics in some cases. A minority of pathologists employ this test. FGFR3 mutations are common in bladder cancer, and metastatic urothelial carcinoma (UC) with such mutations frequently responds to erdafitinib, an FGFR inhibitor. Testing for FGFR3 alterations is required before using this drug. Metastatic UC responds to immune-oncology (IO) agents in 20% of cases. These are approved as first and second-line treatments in metastatic UC. Several biological parameters associate with response to IO agents, including tumor mutational burden, molecular subtype, and infiltration by programmed death-ligand 1-positive lymphocytes, detected by immunohistochemistry. Programmed death-ligand 1 immunohistochemistry is mandatory before administering IO agents in the first-line setting. In conclusion, much has been learned about the biology of bladder cancer, and this understanding has improved the care of patients with the disease.

Altered Expression of the Transcription Factor Forkhead Box A1 (FOXA1) Is Associated With Poor Prognosis in Urothelial Carcinoma of the Upper Urinary Tract.

OBJECTIVE: To determine the prognostic significance of Forkhead Box A1 (FOXA1) expression in patients with upper tract urothelial carcinoma (UTUC) undergoing radical nephroureterectomy (RNU). MATERIALS AND METHODS: A retrospective analysis of 566 patients undergoing RNU at seven academic medical centers was performed. Tissue microarrays were subjected to immunohistochemistry using a commercially available polyclonal FOXA1 antibody. Logistic regression determined the association of FOXA1 expression with pathologic features and survival outcomes. RESULTS: Three hundred twenty-two men and 244 women were included. The pathologic distribution of specimens included 53% muscle-invasive or greater (≥pT2), 74% high-grade, 16% with flat architecture, 13% with necrosis, 21% with lymphovascular invasion, 18% with concomitant carcinoma in situ, and 8% with positive lymph nodes. The median FOXA1 score was 5.0 (range: 0-8). Lower FOXA1 expression was significantly correlated with advanced pathologic stage (≥pT3) (P = .02), concomitant carcinoma in situ (P = .006), and renal pelvis (vs ureter) location (P < .0001). At a median follow-up of 27.0 months (range: 3-196), 139 patients (25%) experienced disease recurrence and 121 (21%) died from the disease. In a multivariate model, lower FOXA1 expression was independently associated with disease recurrence (hazard ratio [HR]: 1.11, 95% confidence interval [CI]: 1.05-1.62, P = .04), cancer-specific mortality (HR: 1.17, 95% CI: 1.03-1.92, P = .04), and all-cause mortality (HR: 1.08, 95% CI: 1.02-1.18, P = .05). CONCLUSION: Lower FOXA1 expression is associated with adverse pathologic features and inferior survival outcomes for UTUC patients undergoing RNU. These data indicate lower FOXA1 expression may be a marker of aggressive disease in UTUC.