4538 Background: Optical coherence tomography (OCT) is a new biotissue imaging technique with spatial resolution approaching cellular level (10 to 15 μm). OCT can acquire real time in vivo structural images at a depth up to 2 mm. This multicenter study assessed OCT endoscopic diagnostic accuracy for suspicious bladder mucosal and subepithelial areas and for intraoperative adequate resection at tumor borders. Methods: A total of 102 patients were evaluated with 3 scans at each site with images compared to histopathology. Prospective analysis was performed in 95 patients (Group 1) undergoing cystoscopy and retrospective analysis in 7 patients with suspicious lesions (Group 2). Biopsies were obtained in normal and suspicious areas. OCT evaluated tumor borders during partial cystectomy or transurethral resection in 31 patients. Results: In Group 1, 63 of 95 had abnormal areas (31 benign, 32 dysplastic/malignant) with sensitivity of 98%, specificity 72%, positive predictive value (PPV) 78% and negative predictive value (NPV) 98%. In Group 2 with known lesions, sensitivity was 86%, specificity 90%, PPV 75% and NPV 95%. Histological comparison of tumor borders in 50 patients with abnormal scans revealed a 74% confirmation of results with 26% having border extension by OCT due to inflammation. In 6 cases (12%) OCT and the histological tumor extent was found more than 2 cm farther than visual border. No cancer recurrence has been found in 31 of 32 patients in Group 1 with minimal follow up of 15 months. Conclusions: This study suggests that OCT is a promising technology to evaluate bladder lesions found during cystoscopy and tumor extent during resection. High sensitivity and specificity with strong interobserver agreement on OCT strongly supports further evaluation of this as an adjunct to standard evaluation in selected cases. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Imalux Corp. Imalux Corp Imalux Corp. Imalux Corporation