Previous studies have reported the efficacy of Bacillus Calmette-Guérin (BCG) combined with other drugs for the treatment of bladder cancer. However, research on the combination of tislelizumab and BCG for bladder cancer treatment has largely been retrospective. Currently, ongoing clinical trials have not discussed the effectiveness of PD-1/PD-L1 inhibitors combined with BCG instillation in reducing postoperative recurrence in intermediate-risk NMIBC. Therefore, this study aims to explore the clinical efficacy and safety of tislelizumab combined with BCG in the treatment of intermediate and high-risk NMIBC. For this purpose, investigators have established strict screening criteria to include eligible patients in the study and have recruited suitable patients from multiple medical centers.Investigators have also developed a meticulous implementation process and follow-up considerations, hoping to better verify the clinical efficacy and safety of the combined use of these two drugs.

Inclusion Criteria:

1. Voluntary participation in the trial with signed informed consent;
2. Patients aged ≥18 and ≤75 years, regardless of gender, with an expected survival of ≥2 years;
3. Histologically confirmed non-muscle-invasive bladder urothelial carcinoma with positive PD-L1 expression. According to the 2014 guidelines of the Chinese Urological Association (CUA), patients are assessed as having a medium to high risk of recurrence or progression. (For patients considering a second transurethral resection, they may be included in the study after completing the procedure and if pathology confirms medium to high risk non-muscle-invasive bladder urothelial carcinoma);
4. Performance status score (Eastern Cooperative Oncology Group, ECOG) of 0-2;
5. Completion of screening-related examinations (complete blood count, coagulation function, liver and kidney function, infectious disease screening, 12-lead ECG, urinary system ultrasound, pelvic MR, and tissue pathology examination), without surgical contraindications.

Exclusion Criteria:

1. Any of the following conditions:

   Immune deficiency or impairment (such as AIDS patients), current use of immunosuppressive drugs or radiation therapy that may cause systemic BCG disease reaction; allergy to BCG components; patients with fever and acute infectious diseases, including active tuberculosis or those undergoing anti-tuberculosis treatment; those with severe chronic cardiovascular or cerebrovascular diseases or chronic kidney disease;

2. Concurrent urogenital system tumors or tumors in other organs;

3. Muscle-invasive bladder urothelial carcinoma (stage T2 and above) patients;

4. Patients who have received chemotherapy, radiotherapy, or immunotherapy within the past 4 weeks (except immediate postoperative bladder instillation chemotherapy);

5. Pregnant or lactating women, women of childbearing age not using effective contraception, or those planning to conceive during the trial period (including male participant partners);

6. Known or suspected intraoperative bladder perforation;

7. Presence of gross hematuria prior to enrollment, suspected unhealed surgical wounds or damaged urinary mucosa;

8. Severe urethral stricture preventing cystoscopy, history of bladder contracture, or functional bladder volume less than 100mL;

9. Accompanying cystitis, or those who have received other bladder instillation medications and have severe bladder irritation signs expected to affect the assessment of this study;

10. Patients with various mental disorders, severe coagulation function, liver and kidney function, hematopoietic function disorders, etc., that cannot tolerate surgical treatment;

11. Participation in other drug clinical trials within 3 months before enrollment;

12. Known or suspected opioid or alcohol dependence;

13. Any condition that the researcher believes may increase the risk to the participant or interfere with the execution of the clinical trial.