Apparent Plasticity In The Biological Response To Neoadjuvant Chemotherapy In Muscle-Invasive Bladder Cancer.

433Background: After cisplatin-based neoadjuvant chemotherapy (NAC) almost two thirds of patients have residual muscle-invasive bladder cancer (MIBC) present at radical cystectomy (RC). The alterations induced by NAC in these cisplatin-resistant tumors remain largely unstudied. Here, we aim to investigate the characteristics of cisplatin-resistant tumors. Methods: RC samples were available for gene expression analysis from 133 patients with residual invasive disease after cisplatin-based NAC, of whom 116 had matched pre-NAC samples. In addition, the tumor bed (scar tissue) of 21 post-NAC RC specimens with no residual tumor was profiled. Unsupervised consensus clustering (CC) was performed and the CC were investigated for their biological and clinical characteristics. Hu0026E and immunohistochemistry (KRT5/6, GATA3, KI67 and CD8) were used to confirm tissue sampling and gene expression analysis. Results: Unsupervised consensus clustering yielded four distinct consensus clusters (CC). Consistent basal-(CC1) and...