Objective:To explore the efficacy of adjuvant chemotherapy and adjuvant immunotherapy combined chemotherapy after radical cystectomy for muscle-invasive bladder cancer (MIBC) with high recurrence risk (pT 2 with positive lymph nodes, and pT 3-4a with or without positive lymph nodes). Methods:A retrospective analysis was conducted on clinical data of 217 patients with bladder cancer admitted to Tianjin Medical University Second Hospital from August 2016 to January 2022. Among them, 183 were male (84.3%) and 34 were female (15.7%), with an average age of (67.3±8.6) years old. All 217 patients underwent radical cystectomy with pelvic lymph node dissection. Based on postoperative adjuvant treatment, the patients were divided into an observation group (147 cases, 67.7%) and a treatment group (70 cases, 32.3%). The observation group and treatment group had similar demographic and pathological characteristics. The age of the observation group and treatment group was (67.4±9.0) years and (66.3±7.6) years, respectively ( P=0.14). The postoperative pathological stages T 2 with lymph node positivity were observed in 8 cases (5.4%) in the observation group and 6 cases (8.6%) in the treatment group. For stages T 3-4awith lymph node positivity, there were 34 cases (23.1%) in the observation group and 18 cases (25.7%) in the treatment group. And there were 105 cases (71.5%) in the observation group and 46 cases (65.7%) in the treatment group of stages T 3-4a without lymph node positivity, respectively( P>0.05). Tumor diameter ≥3 cm was found in 118 cases (80.3%) in the observation group and 54 cases (77.1%) in the treatment group ( P>0.05), while tumor diameter <3 cm was observed in 29 cases (19.7%) in the observation group and 16 cases (22.9%) in the treatment group ( P>0.05).In the treatment group, 36 patients (16.6%) received postoperative chemotherapy with gemcitabine (1 000 mg/m 2, days 1 and 8) and cisplatin (75 mg/m 2, days 2 to 4) (chemotherapy group), while 34 patients (15.7%) received postoperative immunotherapy with checkpoint inhibitors (intravenous infusion of sintilimab 200 mg, terlizumab 200 mg, or toripalimab 240 mg on day 1) in combination with albumin-bound paclitaxel (200 mg on day 2)(immunotherapy combined chemotherapy group). The age of the chemotherapy group and immunotherapy combined chemotherapy group was (66.8±8.4) years and (65.8±6.8) years, respectively ( P>0.05). Postoperative pathological stages T 2 with lymph node positivity were observed in 3 cases (8.3%) in the chemotherapy group and 3 cases (8.8%) in the immunotherapy combined chemotherapy group ( P>0.05). For stages T 3-4awith lymph node positivity, there were 6 cases (16.7%) in the chemotherapy group and 12 cases (35.3%) in the immunotherapy combined chemotherapy group. And there were 27 cases (75.0%) in the observation group and 19 cases (55.9%) in the treatment group of stages T 3-4a without lymph node positivity, respectively( P>0.05). Lymph node involvement was seen in 9 cases (25.0%) in the chemotherapy group and 15 cases (44.1%) in the immunotherapy combined chemotherapy group ( P>0.05). Tumor diameter ≥3 cm was found in 30 cases (83.3%) in the chemotherapy group and 10 cases (29.4%) in the immunotherapy combined chemotherapy group ( P>0.05), while tumor diameter <3 cm was observed in 6 cases (16.7%) in the chemotherapy group and 24 cases (70.6%) in the immunotherapy combined chemotherapy group ( P>0.05). Kaplan-Meier method and multivariate Cox regression test were used to analyze the overall survival (OS) at 1 and 3 years in the observation group and treatment group, as well as the disease-free survival (DFS) at 1 and 3 years in the chemotherapy group and immunotherapy combined chemotherapy group. Additionally, common adverse events were evaluated and compared between the chemotherapy group and immunotherapy combined chemotherapy group based on the criteria published by the U. S. Department of Health and Human Services. Results:The median follow-up time in this study was 18.4 (8.2, 34.7) months. The median follow-up time in the observation group and treatment group was 19.0 (8.3, 35.2) months and 17.5 (7.9, 33.2) months, respectively. The 1-year survival rate was significantly higher in the treatment group compared to the observation group (90.0% vs. 76.2%, χ2=6.92, P=0.009). Similarly, the 3-year survival rate was significantly higher in the treatment group compared to the observation group (82.9% vs. 57.8%, χ2=13.22, P<0.01). The median OS was 35.9 months in the observation group and was not reached in the treatment group, with a statistically significant difference ( HR=2.51, 95% CI 1.36-4.65, P=0.003).In the chemotherapy group and immunotherapy combined chemotherapy group, the median follow-up time was 10.7 (7.4, 22.1) months and 14.4 (6.3, 40.7) months, respectively. The 1-year disease-free survival rate was significantly higher in the immunotherapy combined chemotherapy group compared to the chemotherapy group (91.2% vs. 67.6%, χ2=4.60, P=0.032). The 3-year disease-free survival rate was significantly higher in the chemotherapy group compared to the immunotherapy combined chemotherapy group (88.2% vs. 55.6%, χ2=8.37, P=0.004). The median DFS was 27.7 months in the chemotherapy group and was not reached in the immunotherapy combined chemotherapy group, with a statistically significant difference ( HR=3.39, 95% CI 1.46-7.89, P=0.016).The treatment group had complications classified as follows: 140 cases of grade 1, 39 cases of grade 2, 8 cases of grade 3, 2 cases of grade 4, and 0 case of grade 5 adverse reactions. In the chemotherapy group and the immunotherapy combined chemotherapy group, there were both 5 cases with adverse reactions of grade 3 or higher. Specifically, in the chemotherapy group, there were 2 cases of anemia, 2 cases of decreased platelet count, and 1 case of decreased neutrophil count. In the immunotherapy combined chemotherapy group, there was 1 case of anemia, 1 case of decreased platelet count, and 2 cases of decreased neutrophil count. Additionally, there was 1 case with elevated gamma-glutamyltransferase (γ-GT) in the immunotherapy combined chemotherapy group. The incidence of adverse events of grade 3 or higher in the chemotherapy group and immunotherapy combined chemotherapy group was 13.9% and 14.7%, respectively, with no statistically significant difference( χ2=0.01, P=0.922). Conclusions:Adjuvant therapy significantly prolongs the overall survival in high risk of recurrence for MIBC patients after radical cystectomy. For patients intolerant to platinum-based chemotherapy or refusing platinum-based adjuvant chemotherapy, immunotherapy with checkpoint inhibitors combined with albumin-bound paclitaxel can be considered as an effective and well-tolerated adjuvant treatment after radical cystectomy.