After TURBT, 10%-67% of patients will recur within 12 months, and 24%-84% of patients will recur within 5 years after surgery, mainly due to ectopic recurrence. The main reasons for recurrence are: (1) the primary tumor is not excised; (2) the tumor cells are shed and implanted during surgery; (3) it comes from the proliferation of the pre-existing metastatic epithelium or atypical lesions; (4) the bladder epithelium continues to be stimulated by intra-urinary carcinogenic substances. There are two peak periods of recurrence after TURBT for non-muscle invasive bladder cancer, 100-200 days postoperatively and 600 days postoperatively, respectively. The first peak of postoperative recurrence is associated with intraoperative tumor cell dissemination, and postoperative bladder perfusion therapy can greatly reduce recurrence due to tumor cell dissemination. Although TURBT theoretically allows complete resection of non-muscle-infiltrating bladder cancer, there is a high probability of recurrence in clinical management and some cases progress to muscle-infiltrating bladder cancer. TURBT alone does not address the high postoperative recurrence and progression, and therefore adjuvant bladder perfusion therapy is recommended for all patients with non-muscle invasive bladder cancer postoperatively. (1) Immediate bladder perfusion chemotherapy after TURBT: This means that intravesical perfusion of chemotherapeutic agents is completed within 24 hours after TURBT. For patients with low-risk non-muscle invasive bladder cancer, chemotherapy drugs such as epirubicin or mitomycin can be infused immediately after surgery. The probability of tumor recurrence is very low, so bladder infusion therapy can not be continued after immediate infusion. However, the killing effect of chemotherapeutic drugs on tumor cells all follow the principle of primary kinetics, i.e., they can only kill/injure most of the tumor cells, but not all of them, so the regimen of maintenance bladder perfusion chemotherapy is still recommended for patients with relatively high-risk bladder tumors. In addition, for patients with intraoperative bladder perforation or large surgical trauma of multiple bladder tumors, immediate bladder perfusion chemotherapy is also not recommended to avoid adverse effects caused by absorption of chemotherapy drugs. (2) Early postoperative bladder perfusion chemotherapy and maintenance bladder perfusion chemotherapy: For intermediate-risk and high-risk non-muscle invasive bladder cancer, after immediate bladder perfusion therapy within 24 hours after surgery, it is recommended to continue bladder perfusion chemotherapy once a week for 4-8 weeks, followed by maintenance bladder perfusion chemotherapy once a month for 6-12 months. Studies have shown that maintenance perfusion therapy for non-muscle invasive bladder cancer does not continue to reduce the probability of tumor recurrence at more than 6 months, so postoperative maintenance bladder perfusion therapy for 6 months is recommended. However, some studies have found that epirubicin maintenance perfusion for 1 year reduces the probability of bladder tumor recurrence. In case of severe bladder irritation during instillation, instillation therapy should be delayed or stopped to avoid secondary bladder contracture.2. Postoperative bladder instillation immunotherapy (1) BCG: BCG is a commonly used biological agent for intracavitary bladder instillation, which is a live biological bacterium with certain antigenicity, sensitization and residual toxicity, and is more effective in superficial, non-myeloablative infiltrated bladder tumors and carcinoma in situ. Its anti-tumor mechanism is still not very clear, but there are two points that are relatively clear at present: (1) BCG causes inflammatory response in bladder mucosa after contact with bladder mucosa, which stimulates local cellular immune response and forms collagen fiber-encapsulated fibroblasts, macrophages, and lymphocyte clusters to interfere with tumor cell growth. (2) BCG has direct cytotoxic effects on mucosal epithelial cells and tumor cells; Michael et al. (1991) found that BCG adheres to metastatic epithelial tumor cells and in vitro cultured bladder cancer cell lines T24 and MBT22 and is taken up by these cells, which subsequently lyse the cells through bacterial proliferation or produce certain toxic products that have toxic effects on the cells. BCG bladder perfusion is suitable for the treatment of high-risk non-muscle invasive bladder cancer and can prevent the progression of bladder tumors. However, BCG cannot alter the course of low-risk non-muscle invasive bladder cancer, and because of the high incidence of side effects associated with BCG instillation, BCG instillation is not recommended for low-risk non-muscle invasive bladder uroepithelial cancer. For intermediate-risk non-muscle-infiltrating bladder uroepithelial carcinoma, the probability of tumor recurrence after surgery is 45%, while the probability of progression is 1.8%. Therefore, the main purpose of bladder perfusion for intermediate-risk non-muscle-infiltrating bladder uroepithelial carcinoma is to prevent tumor recurrence, and bladder perfusion chemotherapy is generally recommended, and BCG perfusion therapy can also be used in some cases. The dose of BCG bladder perfusion: BCG treatment generally uses 6 weeks of perfusion to induce an immune response, plus 3 weeks of perfusion intensification to maintain a good immune response; BCG perfusion is generally used at a conventional dose (120-150 mg) for the treatment of high-risk non-muscle-infiltrating bladder uroepithelial carcinoma; BCG is generally used at a low dose (60-75 mg) for the prevention of recurrence of non-muscle-infiltrating bladder uroepithelial carcinoma. 75 mg). It was found that the efficacy of 1/4 dose (30-40 mg) of BCG infusion for the treatment of intermediate-risk non-muscle-infiltrating bladder uroepithelial carcinoma was the same as that of the full dose, but with significantly lower side effects. The efficacy did not differ between BCG strains, and BCG infusion was generally initiated 2 weeks after TURBT. maintenance BCG infusion reduced the probability of bladder tumor progression by 37%. Maintenance BCG instillation is required for 1 to 3 years (at least 1 year of maintenance instillation), therefore some literature recommends repeat BCG instillation at 3, 6, 12, 18, 24, and 36 months to maintain and intensify the efficacy. The main side effects of BCG bladder instillation are bladder irritation and systemic flu-like symptoms. Rare side effects include tuberculosis sepsis, prostatitis, epididymitis, and hepatitis. Therefore, BCG bladder irrigation should not be performed in cases such as open bladder trauma or sarcoid hematuria after TURBT to avoid serious side effects. Patients with immune deficiencies, such as congenital or acquired immunodeficiency syndrome (AIDS), organ transplant patients or other immunocompromised patients, should not be treated with BCG because it will not be effective. Patients with active tuberculosis should also not be treated with BCG infusion as it may cause deterioration of the disease. (2) Immunomodulators: Some immunomodulators can prevent bladder tumor recurrence as well as chemotherapy drugs, including interferon, interleukin-2 (IL-2), and keyhole limpet hemocyanin (KLH). IFN is a glycoprotein, the most commonly used biological agent for intravesical perfusion, which is able to upregulate the host’s immune response and has antiviral, antiproliferative and immunomodulatory effects. Intravesical application of recombinant IFN can increase the cytotoxic effect of NK cells and cytotoxic T lymphocytes by increasing the infiltration of immune cells in the bladder wall, i.e., it has the function of enhancing both the systemic immune system and the local immune function in the bladder. The recommended dose of IFNα for intravesical infusion is 1×107 U/dose to 1×108 U/dose. The side effects of intravesical IFNα are relatively mild, with an incidence of 27%, mainly fever, chills, fatigue and muscle pain similar to flu symptoms. IL-2 is another commonly used immunomodulator. Intravesical instillation or tumor site injection is usually used to achieve better efficacy, but the dose and protocol of use are yet to be standardized.