Literature search
A total of 1451 studies were identified after the initial search. After deletion of 631 duplicates, 771 studies were additionally excluded by careful review of the title and/or abstract. After screening the title and abstract, 49 studies were evaluated via full-text articles. At last, seven articles[7, 12-17] published were included for quantitative synthesis from 2016 to 2018. The flow diagram were summarized is shown in Fig. 1.
Study characteristics
Based on the inclusion and exclusion criteria, seven retrospective studies were included for this review. The characteristics of each study were shown in Table 1. The seven studies included a total of 592 patients: PG-DT was performed in 347 patients and TG was performed in 245 patients. The sample size of each study varied from 30 to 248 patients. All patients received laparoscopic or robotic surgery, of which 533 cases (90.0%) of belonged to stage I proximal gastric cancer. In the PG-DT group, 331 patients (95.4%) were stage I proximal gastric cancer, and in the TG group, 202 cases (82.4%) were stage I proximal gastric cancer.
Patient's clinicopathologic features
In the analysis of patients' basic conditions, there were differences in gender (OR=1.89, 95%CI=1.26-2.84, p=0.002, fixed-effects model) and American Society of Anesthesiologist (ASA) (OR=0.43, 95%CI=0.22-0.83, p=0.01, fixed-effects model) between both groups of patients underwent surgical treatment (LPG-DT vs. LTG). In terms of tumor lesion, patients with LPG-DT had smaller tumor sizes than those with LTG (WMD=-0.94, 95%CI=-1.26-(-0.62), p<0.001, fixed-effects model). The T stage (OR=2.21, 95%CI=1.17-4.17, p=0.01, fixed-effects model) and tumor stage (OR=2.70, 95%CI=1.35-5.39, p=0.005, fixed-effects model) were earlier in the LPG-DT group. However, there was no significant difference in N Stage between both groups (OR=0.77, 95%CI=0.34-1.71, p=0.52, fixed-effects model) (Table 2).
Surgical conditions and Short-term outcomes
In terms of surgical conditions, patients in the LTG group had longer proximal (WMD=-0.97, 95%CI=-1.80-(-0.14), p=0.02, random-effects model) and distal resection margins (WMD=-8.30, 95%CI=-9.57-(-7.03), p<0.001, random-effects model) and more retrieved lymph nodes (WMD=-11.28, 95%CI =-13.52-(-9.04), p<0.001, fixed-effects model). However, there was no significant difference in operative time (WMD=-10.43, 95%CI=-25.64-4.77, p=0.18, random-effects model) and intraoperative blood loss (WMD=3.74, 95%CI = -57.37-64.84, p=0.90, random-effects model) between both groups (Table 2).
Besides, there was no significant difference in short-term outcomes between both groups, including postoperative the length of hospital stay (WMD=-0.21, 95%CI=-1.21-0.80, p=0.68, fixed-effects model), all complications (Clavien-Dindo Grade I or more) (OR=0.87, 95%CI=0.36-2.13, p= 0.76, random-effects model), severe complications (Clavien-Dindo Grade III or more) (OR=0.35, 95%CI=0.12-1.07, p=0.07, fixed-effects model), and anastomotic leakage (OR=0.81, 95%CI=0.34-1.94, p=0.64, fixed-effects model) (Table 2).
Long-term outcomes
The long-term results including anastomotic stenosis, reflux, hematological status, vitamin B12, and oncological outcomes were analyzed. There was also no statistically significant difference between anastomotic stenosis (OR=0.91, 95%CI=0.33-2.50, p=0.85, fixed-effects model) and reflux (OR=1.87, 95%CI=0.62-5.65, p=0.27, fixed-effects model) (Fig. 2). By comparing the hematological and nutritional outcomes between both groups, body mass index (BMI) was mentioned in five studies, among which three showed statistical difference and two showed no statistical difference. Hemoglobin was investigated in six studies, among which only one showed statistical difference, while the other five showed no statistical difference. Ferritin was mentioned in two studies, they all showed no statistical difference. In addition, there were many studies investigated total protein, albumin, total cholesterol and total lymphocyte count, none of the results were statistically significant (Supplementary Table 2). Four of these studies reported postoperative vitamin B12. The vitamin B12 supplementation rate in the LPG-DT group was lower than the LTG group (OR=0.06, 95%Cl=0.01-0.59, p=0.02, random-effects model) (Fig. 2). At the end of follow-up, no patients underwent LPG-DT had recurrence or death. In the LTG group, a total of 4 patients relapsed.