Bladder cancer is the ninth most frequently diagnosed malignancy in the world  and is the fourth leading cause of death among men . The 5-year recurrence rate of non-muscle-invasive bladder cancer ranges from 50–70%, and the reported 5-year progression rate ranges from 10–30% .Transurethral resection of bladder tumor (TURBT) with intraoperative detection of the cancer by white light (WL) is the standard treatment for non-muscle invasive bladder cancer . However, it is difficult to detect flat lesions, including carcinoma in situ (CIS), with WL alone, and the high rate of intravesical recurrence of CIS is problematic. Therefore, it is important to accurately detect CIS in order to be able to remove any residual tumor. It is known that the addition of photodynamic diagnosis (PDD) and narrow-band imaging (NBI) to WL increases the detection rate of cancer in flat lesions that do not appear as distinct lesions with conventional WL [5–8]. PDD and NBI are also associated with lower recurrence rates compared to WL only [2, 9–11]. PDD is a technique that exploits the property of tumors or rapidly proliferating cells to emit red fluorescence during cystoscopy using blue light, after oral or intravesical administration of a photosensitizing precursor such as 5-aminolevulinic acid (5-ALA). NBI is a technique that utilizes the fact that tissue penetration by light depends on its wavelength. By exposing the bladder wall to light with two narrow-banded wavelengths, which are easily absorbed by hemoglobin, capillaries on the surface of the mucosa are displayed as brown and blood vessels inside the submucosa as blue-green, highlighting the tumor. PDD using 5-ALA (5-ALA-PDD) for non-muscle invasive bladder cancer reduces the risk of recurrence  and has a real-world sensitivity and specificity of 90.1% and 61.2%, respectively . For NBI, a meta-analysis showed that the pooled sensitivity and specificity for non-muscle invasive bladder cancer were 94.8% and 65.6%, respectively .
The 2021 European Association of Urology guidelines strongly recommend taking biopsies from both abnormal-looking urothelium and normal-looking mucosa (mapping biopsies from the trigone, bladder dome, right, left, anterior, and posterior bladder wall) when cytology is positive, in case of a history of high grade tumors, and for tumors with non-papillary appearance. Moreover, PDD-guided biopsies should be used if equipment is available. However, bladder biopsy using NBI during TURBT is weakly recommended .
Some studies have examined the usefulness of combining PPD and NBI for the detection of flat lesions [16, 17]. However, no comparative studies exist between 5-ALA-PPD and NBI for the detection of urothelial carcinoma, including both protruded and flat lesions. The purpose of this study was to compare 5-ALA-PDD and NBI in terms of bladder cancer detection capability in the same patients.