Bladder cancer is the most common malignant tumor of the urinary system in China, and its incidence has been increasing year by year. It is classified into non-muscle-invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC). NMIBC accounts for 75% of newly diagnosed bladder cancer cases, and transurethral resection of bladder tumor (TURBT) followed by postoperative intravesical therapy is the standard treatment for NMIBC. However, the 5-year recurrence rate of NMIBC remains as high as 50%, with 20-30% of patients progressing to MIBC. MIBC is characterized by rapid progression and a high tendency for metastasis. The 5-year survival rate for patients with metastatic bladder cancer is only 5.4%. This study aims to investigate the efficacy of submucosal injection of the chemotherapeutic agent gemcitabine in preventing recurrence of intermediate- and high-risk NMIBC. Additionally, it seeks to develop software and devices related to submucosal injection to promote the clinical application of this new approach in the chemotherapeutic management of NMIBC. This research is expected to bring a revolutionary breakthrough in the standardisation of whole-process diagnosis and treatment of NMIBC, holding significant scientific value and major clinical translational importance for improving therapeutic outcomes and prognosis of bladder cancer.

Bladder cancer is a common malignant tumor of the urinary system. Globally, in 2023, there were approximately 610,000 new cases of bladder cancer and about 220,000 deaths attributed to the disease. In China, over the past two decades, the age-standardized incidence and prevalence rates of bladder cancer in men have increased by 71.79% and 195.38%, respectively. Over the last 15 years, the average annual mortality rate for male bladder cancer has risen by 3.84%, posing a serious threat to public health.

Bladder cancer is classified into non-muscle-invasive bladder cancer (NMIBC) and muscle-invasive bladder cancer (MIBC) based on whether the tumor invades the muscle layer. NMIBC accounts for approximately 75% of newly diagnosed bladder cancer cases. The standard treatment for NMIBC involves transurethral resection of bladder tumor (TURBT) followed by postoperative intravesical therapy. However, NMIBC often recurs within one year, with a recurrence rate as high as 60-70%, and 20-30% of cases progress to MIBC. Once bladder cancer advances to MIBC, it is characterized by rapid progression and a high tendency for metastasis. The standard treatment for MIBC is radical cystectomy with lymph node dissection, often accompanied by neoadjuvant or adjuvant chemotherapy. Traditional radical surgery for bladder cancer is highly invasive, associated with slow postoperative recovery and a high incidence of complications. The objective response rate for neoadjuvant or adjuvant chemotherapy is less than 50%. The 5-year survival rate for MIBC is below 60%, and for patients with distant metastasis, it drops significantly to just 5.4%.

In recent years, cancer immunotherapy, particularly immune checkpoint inhibitors, has advanced rapidly. However, immunotherapy also suffers from a low objective response rate, which is even below 30% in MIBC. Therefore, the high incidence, recurrence rate, and difficulty in curing bladder cancer remain significant challenges for both clinicians and patients.

TURBT is the standard surgical procedure for NMIBC. Intravesical therapy is a local adjuvant treatment used after TURBT to prevent recurrence. However, the efficacy of intravesical therapy is limited by inadequate drug absorption, resulting in insufficient local drug concentrations and suboptimal therapeutic outcomes. Moreover, postoperative intravesical therapy involves long-term, repeated invasive procedures, which often lead to complications such as urinary tract infections, bladder irritation, and urethral strictures. Improving the efficiency of drug utilization in intravesical therapy is a promising approach to address these issues. Enhancing drug absorption and prolonging the sustained-release effect of the agents could improve treatment efficacy while reducing the frequency of intravesical instillations, ultimately improving the prognosis of NMIBC, lowering recurrence rates, and reducing the risk of progression to MIBC. Submucosal injection of chemotherapeutic drugs offers a potential solution by increasing drug utilization efficiency and reducing complications associated with intravesical therapy.

Inclusion Criteria:

1. Patients aged 18 to 80 years (inclusive) with radiologically confirmed bladder tumor and scheduled to undergo transurethral resection of bladder tumor (TURBT).
2. Postoperative pathological confirmation of intermediate- or high-risk non-muscle-invasive bladder cancer (NMIBC).
3. Voluntarily participate in the study and sign the informed consent form, ensuring the patient fully understands the trial purpose, risks, and right to withdraw.

Exclusion Criteria:

1. Preoperative comorbidities including detrusor overactivity, urethral stricture, urge incontinence, stress incontinence, or overflow incontinence.
2. Concurrent urogenital infectious diseases (e.g., acute urethritis, acute cystitis).
3. History of pelvic radiotherapy.
4. Receiving systemic anti-tumor therapy for any malignant tumor.
5. Severe cardiovascular disease, hepatic or renal insufficiency, or coagulation dysfunction.
6. Presence of mental illness or psychological disorders that impair normal communication.
7. Any other situation deemed by the investigator as unsuitable for participation in this clinical study.

De-identified individual participant data (IPD) that underlie the results reported in the primary publications of this trial will be shared. This includes data on demographics, tumor characteristics, treatment allocation, recurrence, progression, safety, and quality of life scores.

IPD and supporting documents will become available following the publication of the primary results in a peer-reviewed journal. There is no end date for data sharing.

Data will be accessible to researchers who provide a methodologically sound proposal for approved purposes. Proposals should be directed to the corresponding author. Requestors will need to sign a data access agreement to gain access. A committee led by the principal investigator will review proposals.