Diagnosis of histological type of early gastric cancer by magnifying narrow-band imaging: A multicenter prospective study

Objectives: Distinguishing undifferentiated-type from differentiated-type early gastric cancers (EGC) is crucial for determining the indication of endoscopic resection. We aimed to investigate the diagnostic performance of white-light endoscopy (WLE) and magnifying narrow-band imaging (M-NBI) for the histological type of EGC. Methods: In this multicenter prospective study, patients with histologically proven cT1 EGC, macroscopically depressed or flat type, size >= 5 mm, and without erosion/ulcer, were recruited. The diagnostic criterion of WLE for undifferentiated-type EGC was pale color. The M-NBI algorithm was created based on microsurface and microvascular patterns, and lesions with absent microsurface pattern and opened-loop microvascular patterns were diagnosed as undifferentiated-type. The center of the lesion was defined as the evaluation point and was initially evaluated by WLE, then by M-NBI, and a biopsy specimen was taken as a reference standard. The primary and key secondary endpoints were overall diagnostic accuracy and specificity, respectively. Results: In total, 167 lesions (122 differentiated-type and 45 undifferentiated-type EGCs) in 167 patients were analyzed. The overall accuracy, sensitivity, specificity, and positive likelihood ratio of WLE for undifferentiated-type cancer were 80%, 69%, 84%, and 4.4, respectively, and those of M-NBI were 82%, 53%, 93%, and 7.2, respectively. There was no significant difference in overall accuracy (p = 0.755), but specificity was significantly higher in M-NBI (p = 0.041). Conclusions: The use of M-NBI did not improve the accuracy of WLE for the diagnosis of depressed/flat undifferentiated-type EGCs but improved the specificity. It may reduce surgical overtreatment by preventing misdiagnosis of differentiated-type EGC as undifferentiated-type.