Abstract
Molecular subtyping of muscle-invasive bladder cancer (MIBC) predicts disease progression and treatment response. However, present subtyping techniques are based primarily on transcriptomic analysis, which is relatively expensive. Subtype classification of protein levels by immunohistochemistry (IHC) are more affordable and feasible to perform in a general pathology laboratory. Recent data demonstrated that GATA3, CK20, CK5/6, and CK14 protein levels were correlated with MIBC molecular subtypes. We aimed to evaluate the correlation of those IHC markers with survival outcomes after radical cystectomy in Thai patients. Moreover, we aim to evaluate molecular subtypings by mRNA expression analysis. We evaluated the IHC-based subtypes in MIBC, as classified by GATA3, CK20, CK5/6, and CK14 expression in 132 MIBC patients who underwent radical cystectomy followed by adjuvant chemotherapy (2008–2016). All individual markers and clinicopathological parameters were analyzed against treatment outcomes after radical cystectomy and some selected tissues were sent for whole transcriptome sequencing and clustering from mRNA expression. The result showed that the mean patient age was 65.6 years, and the male to female ratio was 6.8:1. Positive IHC expression rates of GATA3, CK20, CK5/6, and CK14 were 80.3%, 50.8%, 42.4%, and 28.0%, respectively. The 5-year overall survival (OS) was 27.0% (95% confidence interval (CI) 19.6%–35.0%). Only GATA3 and CK5/6 were significantly associated with survival outcome (log-rank p-values = 0.004 and 0.02). GATA3 and CK5/6 were then used to establish subtypes, which were luminal (GATA+ and CK5/6−, 38.6%), basal (GATA− and CK5/6+, 12.9%), mixed (GATA+ and CK5/6+, 37.9%), and double-negative (GATA− and CK5/6−, 10.6%). Patients with the mixed subtype had a significantly better 5-year OS at 42.8%, whereas patients with the double-negative subtype had the worst prognosis among the four groups (5-year OS 7.14%). In the multivariable analysis, lymph node status and subtype independently predicted survival probability. The double-negative subtype had a hazard ratio of 3.29 (95% CI 1.71–6.32). In conclusion, subtyping using GATA3 and CK5/6 was applicable in MIBCs, and patients with the double-negative subtype were at the highest risk and may require more intensive therapy and mRNA subtyping by mRNA expression must showed the significant relationship with survival rate.
