Experienced endoscopists conducted all endoscopic procedures. Intravenous midazolam and pethidine hydrochloride were used to place patients under conscious sedation for endoscopic procedures. During ESD procedures, a single-channel upper gastrointestinal endoscope with a water jet system (GIF-Q260J; Olympus) with a transparent hood (D-201 – 11804; Olympus) attached to the tip of the endoscope and a standard electrosurgical generator (ICC 200 or VIO300D; Erbe Elektromedizin GmbH, Tübingen, Germany) were used. A B-knife or a Flush Knife and an insulation-tipped diathermy knife (IT knife-2; Olympus) were the main electrosurgical knives. A Coagrasper (FD-410LR; Olympus) was also used to stop bleeding or to prevent hemorrhage before vessel cutting. Initially, a hyaluronic acid solution was injected into the submucosal layer around the marking dots to lift it. Next, a needle knife was used to make a circumferential mucosal incision on the oral side around the periphery of the marking dots. After additional submucosal injection below the lesion, submucosal dissection was performed, using the same needle knife, from the oral side toward the anal side. After removing the lesion to the cardia of the stomach, circumferential cutting on the anal side, followed by submucosal dissection, was performed using a retroflex approach with an IT knife-2, and complete en bloc resection was performed. The total procedure time was defined as the period from injection of hyaluronic acid solution to removal of the tumor. Procedure speed (min/cm2) was calculated as the total procedure time (min) divided by the area of the resected specimen (cm2).