[Learning curve for a five-step procedure, transthoracic single-port assisted laparoscopic transabdominal diaphragmatic approach, for Siewert type II adenocarcinoma of the esophagogastric junction].

Objective: To investigate the learning curve for a five-step procedure, namely, a transthoracic single-port assisted laparoscopic transabdominal diaphragmatic approach, for Siewert type II adenocarcinoma of the esophagogastric junction. Methods: In this retrospective cohort study, we analyzed relevant clinical data of 66 patients with Siewert type II adenocarcinoma of the esophagogastric junction who had undergone the five-step procedure performed by the same surgeon in the Gastrointestinal Surgery Department of Guangdong Provincial Hospital of Chinese Medicine from May 2017 to April 2023. The learning curve were plotted using cumulative summation analysis and selected indicators, including intraoperative blood loss, duration of surgery, time to first flatus, time to first tolerance of liquid food, length of hospital stay, and incidence of perioperative complications at different stages were compared. The data were analyzed using SPSS 24.0 statistical software. Numerical data are presented as cases (%) and data were analyzed using the χ² test or Fisher's exact test. Normally distributed measurement data are presented as x±s, and independent sample t-testing was performed for inter group comparison. Non-normally distributed measurement data are presented as M(Q₁, Q₃) and the Mann-Whitney U test was used for inter group comparison. Results: The five-step procedure had been successfully completed without switching to open surgery in all 66 study patients. There were no perioperative deaths, blood loss was 100 (50, 200) mL and duration of surgery 329.4±87.3 minutes. The equation of optimal fit for the duration of surgery was y=0.031x³-4.4757x²+164.97x-264.4 (P<0.001, R²=0.9797). The cumulative summation learning curve reached a vertex when 25 surgical procedures had accumulated. Using 25 cases as the cut-off, we divided the learning curves into learning and proficiency periods and patients into learning (25) and proficiency period groups (41). There were no statistically significant differences between the two groups of patients in sex, age, body mass index, American Society of Anesthesiologists score, history of abdominal surgery, comorbidities, preoperative neoadjuvant therapy, maximum tumor diameter, surgical procedure, or T and N stage of tumor (P>0.05). The following factors differed significantly (all P<0.05) between the learning and proficiency stages: in the latter there was less intraoperative blood loss (100 [50, 100] ml vs. 200 [100, 200] ml, U=-3.940, P<0.001), shorter duration of surgery ([289.8±50.7] minutes vs. [394.4±96.0] minutes, t=5.034, P<0.001), more mediastinal lymph nodes removed (5 [2, 8] vs. 2 [1, 5], U=-2.518, P=0.012), earlier time to first flatus (2 [2, 3] days vs. 4 [3, 6] days, U=-4.016, P<0.001), earlier time to first tolerance of liquid food (5 [4, 6] days vs. 7 [6, 8] days, U=-2.922, P=0.003), shorter duration of hospital stay (8 [8, 10] vs. 10 [9, 12] days, U=-2.028, P=0.043). The incidence of surgical complications did not differ significantly between the two groups (P=0.238). Conclusion: Satisfactory results can be achieved with the five-step procedure for patients with Siewert type II adenocarcinoma of the esophagogastric junction once 25 procedures have been performed.