| Summary: | Background: Intravesical bacillus Calmette-Guérin (BCG) instillation is a standard treatment for non–muscle-invasive bladder cancer (NMIBC); however, not all patients benefit from BCG therapy. Currently, no surrogate marker exists to predict BCG efficacy, and thereby, identify patients who will benefit from this treatment. Objective: To evaluate the utility of urine Mycobacterium tuberculosis complex polymerase chain reaction (MTC-PCR) assay as a predictive marker for recurrence and progression following BCG therapy. Design, setting, and participants: A prospective analysis was carried out for of intermediate- or high-risk NMIBC patients who received BCG instillation for the first time. Urine samples, for MTC-PCR assay, were collected at baseline and annually for up to 10 yr after the last BCG instillation, including induction and maintenance therapy. The first postoperative sample for MTC-PCR was taken at 1 yr from the last instillation. Outcome measurements and statistical analysis: A survival analysis was performed using the Kaplan-Meier method, and risk factors for recurrence and progression after BCG treatment were assessed using Cox regression analysis. Results and limitations: During follow-up (median: 57 mo), 468/521 samples (89.8%) were MTC-PCR positive, and 108/123 patients (87.8%) exhibited MTC-PCR positivity at least once. Five-year recurrence- and progression-free survival in patients who were not MTC-PCR positive was significantly lower than in patients who were MTC-PCR positive at least once (p < 0.001). Using multivariable Cox regression analysis, MTC-PCR positivity at least once was a significant prognostic factor for recurrence (hazard ratio [HR]: 36.782, p < 0.001) and progression (HR: 47.209, p < 0.001). Conclusions: Patients who were not MTC-PCR positive, even once after BCG therapy, were extremely likely to exhibit recurrence and progression. Urine MTC-PCR may be an extremely useful, noninvasive surrogate marker to predict recurrence and progression following BCG therapy. Patient summary: Urine Mycobacterium tuberculosis complex polymerase chain reaction may be a novel biomarker capable of identifying patients at risk of recurrence and progression after bacillus Calmette-Guérin (BCG) immunotherapy.
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