Expression of Nectin-4 in Variant Histologies of Bladder Cancer and Its Prognostic Value—Need for Biomarker Testing in High-Risk Patients?

SIMPLE SUMMARY: Variant histologies of bladder cancer present at advanced stage and are often treated with radical cystectomy. As Nectin-4 appears to be a promising target for novel therapies in conventional bladder cancer, we aimed to analyze the expression of Nectin-4 and its prognostic value in variant histologies of bladder cancer. We found a high expression of Nectin-4 in squamous cell carcinoma and adenocarcinoma and a low expression in sarcomatoid urothelial carcinoma. No impact of Nectin-4 expression on survival has been detected in our study. Our study reveals the need to perform further biomarker testing for Nectin-4 in prospective trials including patients with variant histologies. ABSTRACT: Variant histologies of bladder cancer (BC) often present with advanced tumor stage and the status of perioperative therapy is unclear. Thereby, squamous cell carcinoma (SCC), adenocarcinoma (ADENO), and sarcomatoid urothelial carcinoma (SARCO) are the most frequent variants. Nectin-4 has emerged as a highly interesting target in BC and might guide therapeutic application of antibody–drug conjugates (ADC). We therefore aimed to investigate expression patterns and prognostic value of Nectin-4 in variant histologies of BC. A single-center retrospective analysis was conducted of patients who underwent radical cystectomy (RC) for BC and revealed variant histologies of BC in the final specimens. Immunohistochemical staining for Nectin-4 was performed on tissue microarrays with 59 SCC, 22 ADENO, and 24 SARCO, and Nectin-4 expression was scored using the histochemical scoring system (H-score). Overall survival (OS) and progression-free survival (PFS) was calculated by Kaplan–Meier method. Median expression of Nectin-4 was 150 (range 0–250) in SCC, 140.5 (range 30–275) in ADENO, and 10 (0–185) in SARCO, with significantly lower levels for SARCO compared to SCC or ADENO (p < 0.001). For SCC, ADENO or SARCO no differences regarding OS or PFS were observed based on Nectin-4 expression levels (p > 0.05). Multivariate analysis revealed nodal stage as an independent prognostic factor for OS and PFS and metastases for PFS but not Nectin-4 expression. In conclusion, Nectin-4 was not prognostic in histological subtypes of BC in our study cohort. However, the high expression of Nectin-4 in SCC and ADENO might guide future treatment with novel Nectin-4-directed ADCs and provide this high-risk patient collective with a new promising therapeutic option. Testing Nectin-4 expression as a biomarker should be considered in trials with SARCO, where low Nectin-4 expression has been observed.