The present invention provides therapeutic and diagnostic methods and compositions for bladder cancer (e.g., a locally advanced or metastatic urothelial carcinoma). The invention provides methods of treating bladder cancer, methods of determining whether a patient suffering from bladder cancer is likely to respond to treatment comprising a PD-L1 axis binding antagonist, methods of predicting responsiveness of a patient suffering from bladder cancer to treatment comprising a PD-L1 axis binding antagonist, and methods of selecting a therapy for a patient suffering from bladder cancer, based on expression levels of a biomarker of the invention (e.g., PD-L1 expression levels in tumor-infiltrating immune cells in a tumor sample obtained from the patient).本發明提供針對膀胱癌(例如局部晚期或轉移性尿路上皮癌)之治療及診斷方法以及組成物。本發明提供治療膀胱癌之方法、確定罹患膀胱癌之患者是否有可能響應於包含PD-L1軸結合拮抗劑之治療的方法、預測罹患膀胱癌之患者對包含PD-L1軸結合拮抗劑之治療的反應性的方法，以及基於本發明生物標記物之表現水準(例如，獲自該患者之腫瘤樣品中之腫瘤浸潤免疫細胞中之PD-L1表現水準)為罹患膀胱癌之患者選擇療法的方法。
