A forward-viewing radial-array echoendoscope is useful for diagnosing the depth of colorectal neoplasia invasion

Background It is important to accurately diagnose the depth of colorectal neoplasia invasion. We aimed to evaluate the usefulness of a new forward-viewing radial-array echoendoscope (FRE), relative to the pit pattern method. Methods In this prospective study, the invasion depth of suspected early-stage carcinoma was diagnosed using the pit pattern and FRE methods. The diagnoses were classified as T1a (submucosal invasion distance < 1,000 μm) or shallower and T1b (≥ 1,000 μm) or deeper. Pathological diagnoses were used to compare the diagnostic capabilities of the two methods. Results The final analyses included 110 lesions. The FRE was successfully inserted to the lesion in all cases. There were no significant differences between the two methods regarding the correct prediction rate (79.1% vs. 75.5%, P = 0.57), accuracy (81.3% vs. 79.0%, P = 0.68), specificity (81.3% vs. 70.8%, P = 0.135), positive predictive value (65.0% vs. 60.4%, P = 0.649), negative predictive value (91.0% vs. 98.1%, P = 0.108), or frequency of unevaluable cases (2.7% vs. 4.5%, P = 0.471). The correct prediction rate was calculated by adding the number of unevaluable cases to the denominator of accuracy. Relative to the pit pattern method, the FRE method offered significantly higher sensitivity for predicting T1b or deeper invasion (81.3% vs. 97.0%, P = 0.048). The pit pattern method had significantly poorer accuracy for large lesions (> 36 mm) than for smaller lesions (≤ 36 mm). In contrast, the accuracy of the FRE method did not differ significantly with lesion size. When using the FRE method, no cases were unevaluable because of attenuation. The FRE method provided correct diagnoses in 2 of 3 cases that were unevaluable using the pit pattern method. Conclusions The pit pattern and FRE methods offered similar diagnostic performance for invasion depth. Furthermore, the FRE method may be used to correctly diagnose cases that are unevaluable using the pit pattern method.