This study is a prospective, randomized, multicenter clinical trial aiming to enroll 428 patients with non-muscle-invasive bladder cancer (NMIBC) from the Department of Urology at Jiangsu Provincial People's Hospital and its affiliated centers, who have undergone their initial transurethral resection and are scheduled for a second resection. Within 1-6 weeks after the first resection and prior to the second resection, 100ml of routine urine will be collected and sent within 24 hours to Beijing Genetron Health Clinical Laboratory Co., Ltd. for the extraction of urinary sediment DNA, which will then undergo genome-wide low-depth sequencing. Patients with positive test results will proceed with the second resection, while those with negative results will be randomly assigned in a 1:2 ratio to either the intervention group, which will not undergo a second resection, or the control group, which will undergo the second resection. All enrolled patients will be followed up for two years. The study will statistically analyze and compare the two-year recurrence-free survival rates between the two groups and evaluate the predictive capability of the test results for follow-up recurrence.

Inclusion Criteria:

• Patients with NMIBC who have completed the initial transurethral resection and are scheduled for a second resection, as recommended by guidelines or physician's choice:

  1. Incomplete initial TURBT due to various reasons (including large tumor size, high risk of intraoperative bleeding, extensive tumor range, etc.), posing a risk of residual tumor;
  2. Absence of muscle layer tissue in the initial resection specimen;
  3. Post-initial resection pathology indicating T1 stage;
  4. Post-initial resection pathology indicating G3/high-grade tumor, excluding pure carcinoma in situ;

• Ability to provide a 100ml routine urine sample within 1-6 weeks after the initial resection and before the second resection;

• Age ≥ 18 years;

• Willingness to provide basic clinical information, pathology, and subsequent - recurrence monitoring results;

• Willingness to sign the informed consent form.

Exclusion Criteria:

• Patients with other non-urothelial malignant tumors (including prostate cancer and renal cell carcinoma);
• Patients previously diagnosed with muscle-invasive bladder cancer;
• Patients unable to undergo a second resection;
• Patients with incomplete pathological information of the sample;
• Patients with contaminated samples;
• Patients whose urine samples fail quality control for valid reasons and cannot be resampled;
• Any condition deemed by the investigator as potentially harming the subject or preventing the subject from meeting or fulfilling the study requirements;
• Patients unable to provide written informed consent.

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