Study design
This prospective, randomized, controlled study (registration: www.medresman.org.cn; #ChiCTR2200055966) was performed at Zhejiang Cancer Hospital from January 2017 to January 2021. The study was approved by the Institutional Ethics Review Board of Zhejiang Cancer Hospital (approval number: IRB-2016-157). Written informed consent was obtained from each patient enrolled. The primary endpoint was 3-year OS rate and the secondary endpoints were 3-year DFS rate and the safety.
Enrollment criteria were as follow: (1)first diagnosed AGC patients with T3~T4b confirmed by histologic evidence of resected specimens according to the 7th edition of the TNM classification for gastric cancer[19]; (2) without distant metastasis; (3) age ranges from 18 to 75 years; (4) did not receive any preoperative treatment, such as preoperative chemotherapy or radiotherapy; (5) Eastern Cooperative Oncology Group (ECOG) performance status of 0–1; (6) with white blood cells≥3.5×109/L, neutrophil≥1.5×109/L, platelet≥100×109/L, serum total bilirubin≤1.5-fold of the upper limits of the normal ranges (ULNS), serum creatinine≤1.2-fold ULNS, serum aspartate transaminase (AST) and alanine transaminase (ALT) level≤1.5-fold ULNS. Patients with positive cytology were excluded from the study.
Treatment
All patients were randomly assigned to HIPEC group or non-HIPEC group after radical gastrectomy using a web response system. Patients in HIPEC group received HIPEC treatment and systemic chemotherapy, while patients in non-HIPEC group received only systemic chemotherapy. The treatment-schedule of this study was showed in Figure 1.
I. Surgical treatment
All patients received open or laparoscopic surgery and a distal or total gastrectomy were selected depending on the tumor location. Routine D2 lymph node dissections were performed according to the Japanese gastric cancer treatment guidelines (4th edition)[20]. Different reconstruction methods including Billroth I gastroduodenostomy, Billroth II gastrojejunostomy, and Roux-en-Y esophagojejunostomy were selected based on the extent of gastrectomy. Resected specimens were evaluated by two experienced pathologists to confirm the exact pathological staging. A routine peritoneal cavity washing with at least 1-liter normal saline was performed in both groups after radical surgery.
II. HIPEC
For the patients allocated to HIPEC group, two inflow catheters were inserted in the upper abdomen and two outflow catheters in the pelvic cavity. HIPEC treatment was conducted twice within 72h after gastrectomy. Generally, the first HIPEC treatment was performed within 24h after surgery followed by the second HIPEC at an interval of 24-48h. Approximately 3 liters of heated normal saline containing cisplatin (40mg/m2) was infused into peritoneal cavity at a rate of 500 ml/min and circulated for 60 minutes using a custom-developed high-precision body cavity hyperthermic perfusion treatment system (BR-TRG-II, Bright Medical Technology Co., Ltd., Guangzhou, China). The temperature of the perfusate was maintaining at 43±0.3℃ during the process of intraperitoneal chemotherapy. And the perfusate was drained out after the completion of HIPEC.
III. Postoperative systemic chemotherapy
Postoperative systemic chemotherapy based on SOX regimen (6-8 cycles of S-1 combined with oxaliplatin) was administered for patients in both groups after 4-6 weeks of radical surgery. Oxaliplatin (130mg/m2) was administered intravenously on day 1 and S-1 (80, 100 and 120 mg/day for body surface area below 1.25 m2, between 1.25 and 1.5 m2 and above 1.5m2, respectively) was administered orally, twice a day for two consecutive weeks followed by a one-week rest.
Evaluation and follow up
The postoperative complications were confirmed by investigators according to Clavien-Dindo grading[21] and chemotherapy related adverse events were evaluated according to common terminology criteria for adverse events (CTCAE)[22]. The OS time was calculated from the date of initial diagnosis to the time of death or the date of the last follow-up. The DFS time was defined as the time from surgery to tumor recurrence.
After postoperative systemic chemotherapy, patients were assessed by physical examination, computerized tomography scan or the serum tumor markers every 3 months for the first 2 years, then every 6 months for 3–5 years. The last follow-up was performed in June 2022.
Sample size
According to some previous studies[23, 24], the 3-year overall survival (OS) rate of AGC patients was 74.2%-83% (mean, 78%). After D2 radical resection with HIPEC and systemic chemotherapy, the 3-year OS rate of AGC patients is estimated to be 86%. Assuming a two-sided α of 0.05 and 90% statistical power, with an estimated dropout rate of 15%, the required sample size was estimated to be 130 patients.
Statistical analysis
All data were systematically collected to establish a comprehensive database. The data were analyzed by SPSS software for windows, version 26.0 (SPSS Inc., Chicago, IL, USA). The Chi-squire test was used to compare the differences in age, gender, pathologic stage, differentiation degree, tumor size, tumor location and the occurrence rate of metastases, etc. The survival curves were calculated and compared by Kaplan-Meier method and the log-rank test. A p-value<0.05 was considered as statistically significant. Patients without complete data will not be included in the final analysis.