Prognostic significance of BAP1 expression in high-grade upper tract urothelial carcinoma: a multi-institutional study

Purpose: To evaluate the prognostic value of BRCA1-associated protein-1 (BAP1) expression in upper tract urothelial carcinoma (UTUC), as BAP1 mutations have been associated with prognostic implications in urologic and non-urologic malignancies. Methods: We reviewed a multi-institutional cohort of patients who underwent radical nephroureterectomy (RNU) for high-grade UTUC from 1990–2008. Immunohistochemistry (IHC) for BAP1 was performed on tissue microarrays. Staining intensity was graded from 0–3, with BAP1 loss defined as an average intensity of < 1. Clinicopathologic characteristics and oncologic outcomes [recurrencefree (RFS), cancer-specific (CSS), and overall survival (OS)] were stratified by BAP1 status. The prognostic role of BAP1 was assessed using Kaplan–Meier (KM) and Cox regression analysis. Significance was defined as p < 0.05. Results: 348 patients were included for analysis and 173 (49.7%) showed BAP1 loss. Median follow-up was 36.0 months. BAP1 loss was associated with papillary architecture and absence of tumor necrosis or CIS. On univariable analysis, BAP1 loss was associated with improved RFS (HR 0.60, p = 0.013) and CSS (HR 0.55, p = 0.007), although significance was lost on multivariable analysis (HR 0.71, p = 0.115 and HR 0.65, p = 0.071; respectively) after adjusting for other significant parameters. BAP1 expression was not significantly associated with OS. Conclusions: BAP1 loss was associated with favorable pathologic features and better oncologic outcomes in univariate but not multivariate analysis in patients with high-grade UTUC. In contrast to renal cell carcinoma, loss of BAP1 expression appears to confer a better prognosis in high-grade UTUC. The role of the BAP1 pathway in UTUC pathogenesis remains to be further elucidated.