Safety and efficacy of intravesical bacillus Calmette-Guerin instillation for superficial recurrence following bladder-sparing therapy of muscle invasive bladder cancer.

787 Background: Patients treated with bladder-preserving therapy for muscle-invasive bladder cancer are at risk of developing recurrent non-muscle-invasive bladder cancer. This study aims to evaluate the efficacy and adverse events of postoperative Bacillus Calmette-Guerin (BCG) instillation in patients with superficial recurrence following bladder-preserving therapy for muscle-invasive bladder cancer. Methods: We retrospectively analyzed 120 patients diagnosed with non-muscle-invasive bladder cancer who underwent transurethral resection followed by BCG instillation. The 19 patients with prior muscle-invasive bladder cancer were categorized as the NMIBC-M group, while the remaining 101 patients formed the NMIBC group. All patients completed a six-cycle BCG course. Results: Both groups showed no significant differences in baseline characteristics, except for the number of BCG instillations (15.5 vs. 9, p = 0.010). Overall survival, recurrence-free survival, metastasis, bladder preservation, and adverse event profiles were comparable between groups. However, patients in the group with prior muscle-invasive bladder cancer reported lower rates of urinary retention (28.7% vs. 0.0%, p = 0.017) and fever (30.7% vs. 5.3%, p = 0.044). Conclusions: Postoperative BCG instillation in patients with superficial recurrence following bladder-preserving therapy for muscle-invasive bladder cancer showed comparable efficacy and side effects to those without muscle-invasive bladder cancer history.