Divergent biological response to neoadjuvant chemotherapy in muscle-invasive bladder cancer

Despite cisplatin-based neoadjuvant chemotherapy (NAC) 60% of patients with muscle-invasive bladder cancer still have residual invasive disease at radical cystectomy (RC). The NAC-induced biological alterations in these cisplatin-resistant tumors remain largely unstudied. We analyzed gene expression from 133 patients with residual invasive disease after cisplatin-based NAC. H&E and immunohistochemistry were used to confirm tissue sampling and gene expression analysis. Established molecular subtyping models proved to be inconsistent in their classification of the post-NAC samples. Unsupervised consensus clustering revealed four distinct consensus clusters (CC). The CC1-Basal and CC2-Luminal subtypes expressed genes consistent with a basal-like and a luminal-like phenotype, respectively. The CC3-Immune subtype had the highest immune activity, including T-cell infiltration and checkpoint molecule expression, but lacked both basal and luminal markers. The CC4-Scar-like subtype expressed genes associated with wound-healing/ scarring and was associated with favorable prognosis. RC samples were available for gene expression analysis from 133 patients with residual invasive disease after cisplatin-based NAC. Unsupervised consensus clustering (CC) was performed and the CC were investigated for their biological and clinical characteristics. H&E and immunohistochemistry on tissue microarrays were used to confirm tissue sampling and gene expression analysis.