Probiotics Combined With Targeted Therapy Plus Immunotherapy in Bladder-Preserving Setting for Patients With MIBC

Inclusion Criteria: * Patients have histologically confirmed, radiologically staged cT2-3N0M0 urothelial carcinoma of the bladder, in which urothelial carcinoma is the predominant component (\>50%). * Serum butyrate level \<46 μg/L as determined by quantitative mass spectrometry. * HER2 expression is assessed by immunohistochemistry (IHC) on pretreatment tumor specimens, with confirmed IHC ≥1+. * Patients are deemed ineligible for radical cystectomy based on laboratory evaluation and patient preference. * Patients considered ineligible for cisplatin therapy and meeting at least one of the following criteria: ECOG performance status \>1 or Karnofsky performance status of 60-70%; Creatinine clearance \<60 mL/min; Hearing loss ≥ Grade 2 according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0; Peripheral neuropathy ≥ Grade 2 (NCI-CTCAE v5.0); New York Heart Association (NYHA) Class III or higher heart failure. * ECOG performance status of 0-2. * Adequate cardiac, bone marrow, hepatic, renal, and coagulation functions. Exclusion Criteria: * Prior ADCs or PD-1/PD-L1 inhibitor therapy. * Known hypersensitivity to microbiota-related preparations (microecological products), RC48-ADC or Toripalimab or any of its components. * Receipt of other approved systemic anticancer therapy or systemic immunomodulatory agents (including but not limited to interferon, interleukin-2, and tumour necrosis factor) within 28 days prior to enro…