CA9 and neoplasm: Todenhöfer et al. explored CA9 mRNA expression in patients with MIBC treated with NAC and reported no significant association with pathological outcome.26 Hoskin et al. reported that OS negatively correlates with CA9 positivity in tumor cells (negative vs. low vs. high; p = 0.021).27 However, the rates of NAC were low in these studies and, to our knowledge, no previous study on the chemotherapy response based on CA9 tissue immunohistochemical staining has been reported in urothelial cancer.