Assessment of the Diagnostic Performance of Endoscopic Ultrasonography After Conventional Endoscopy for the Evaluation of Esophageal Squamous Cell Carcinoma Invasion Depth

IMPORTANCE: Distinguishing between mucosal and submucosal cancers is important for selecting the optimal treatment for patients with esophageal squamous cell carcinoma (ESCC); however, standard procedures for diagnosing cancer invasion depth have not yet been determined. OBJECTIVE: To evaluate the diagnostic performance of endoscopic ultrasonography (EUS) after conventional endoscopy for the evaluation of ESCC invasion depth. DESIGN, SETTING, AND PARTICIPANTS: This prospective single-arm confirmatory diagnostic study comprising 372 patients with T1 esophageal cancer was conducted at 41 secondary or tertiary hospitals in Japan. Enrollment began on July 20, 2017; patients were enrolled in 2 steps, with the first registration occurring from August 4, 2017, to December 11, 2019, and the second from August 9, 2017, to December 11, 2019. After the completion of all first and second registration examinations, patients received treatment and were followed up for 30 days, with follow-up ending on February 14, 2020. Patients were eligible for inclusion if they had pathologically or endoscopically diagnosed esophageal cancer with T1 clinical depth of invasion. INTERVENTIONS: In the first registration, nonmagnifying endoscopy (non-ME) and magnifying endoscopy (ME) were used to diagnose cancer invasion depth. In the second registration, patients from the first registration who had cancers invading the muscularis mucosa or submucosa were enrolled and received EUS. After completion of the protocol examinations, patients received treatment with endoscopic resection or esophagectomy. The pathological results of the resected specimens were used as the reference standard for evaluating cancer invasion depth. MAIN OUTCOMES AND MEASURES: The primary end point was the proportion of overdiagnosis of submucosal cancer (defined as invasion depth >200 μm) after receipt of non-ME and ME, with or without the addition of EUS. The secondary end points were underdiagnosis, sensitivity, and specificity. RESULTS: Among 372 patients enrolled in the first registration, 371 received non-ME and ME. Of those, 300 patients were enrolled in the second registration, and 293 patients received EUS. A total of 269 patients (217 men [80.7%]; median age, 69 years; interquartile range, 62-75 years) were included in the final analysis. The addition of EUS was associated with a 6.6% increase in the proportion of overdiagnosis (from 16 of 74 patients [21.6%; 95% CI, 12.9%-32.7%] after non-ME and ME to 29 of 103 patients [28.2%; 95% CI, 19.7%-37.9%] after the addition of EUS; 1-sided P = .93). All subgroup analyses found similar increases in overdiagnosis of submucosal cancer. The addition of EUS was associated with a 4.5% reduction in the proportion of underdiagnosis (from 57 of 195 patients [29.2%; 95% CI, 23.0%-36.2%] after non-ME and ME to 41 of 166 patients [24.7%; 95% CI, 18.3%-32.0%] after the addition of EUS). After non-ME and ME, diagnostic sensitivity was 50.4% (95% CI, 41.0%-59.9%), specificity was 89.6% (95% CI, 83.7%-93.9%), and accuracy was 72.9% (95% CI, 67.1%-78.1%). After the addition of EUS, diagnostic sensitivity was 64.3% (95% CI, 54.9%-73.1%), specificity was 81.2% (95% CI, 74.1%-87.0%), and accuracy was 74.0% (95% CI, 68.3%-79.1%). CONCLUSIONS AND RELEVANCE: This study found that the addition of EUS was not associated with improvements in the diagnostic accuracy of cancer invasion depth. These findings do not support the routine use of EUS after conventional endoscopy for evaluating the invasion depth among patients with T1 ESCC.