Results of the interim analysis of a prospective, multicenter, observational study of small subepithelial lesions in the stomach.

Objectives: Long‐term outcomes of gastric subepithelial lesions have not been elucidated. To reveal the natural history, we initiated a prospective, 10‐year follow‐up of patients with small (≤20 mm) gastric subepithelial lesions in September 2014. Here, we report the results of an interim analysis of a prospective observational study. Methods: In total, 567 patients with 610 lesions were prospectively registered between September 2014 and August 2016. The location, size, morphology, and number of subepithelial lesions were recorded on a web‐based case report form. This study has been conducted as an Academic Committee Working Group of the Japan Gastroenterological Endoscopy Society. Results: The endoscopic follow‐up period was 4.60 ± 1.73 years (mean ± standard deviation), and survival data were investigated for 5.28 ± 1.68 years. This interim analysis revealed that the estimated cumulative incidence of a size increase ≥5 mm, after accounting for patients' death and resection of the tumor as competing risk events, was 4.5% at 5 years. In addition, the estimated cumulative incidence of lesion size increase ≥5 mm or resection of lesions was 7.9% at 5 years, and that of size increase ≥10 mm or resection of lesions was 4.5% at 5 years. Conclusion: These results indicate that approximately one in 13 patients with small (≤20 mm) gastric subepithelial lesions may require resection or further investigation for increased tumor size (≥5 mm) within 5 years. [ABSTRACT FROM AUTHOR]