Dual tracer navigation for lymph node dissection in laparoscopic radical gastrectomy (DANCE trial): a protocol for a prospective, randomized clinical trial

The following are the inclusion criteria: (1) 18–75 years old; (2) primary gastric adenocarcinoma (papillary, tubular, mucinous, signet ring, undifferentiated adenocarcinoma) confirmed pathologically by endoscopic biopsy before surgery; (3) cT1-4a, cNany, cM0 according to the AJCC classification (version 7.0) before surgery; (4) absence of adjacent organ invasion and distant metastasis; (5) ECGO score 0 or 1 and ASA grades I–III; (6) signed informed consent.

The following are the exclusion criteria:(1) pregnant or lactating women. (2) serious mental disease; (3) previous upper abdominal surgery (except laparoscopic cholecystectomy); (4) previous gastric surgery (including ESD and EMR); (5) refusal to laparoscopic surgery; (6) allergy to iodinated contrast agents; (7) peri-gastric LN larger than 3 cm in preoperative imaging; (8) history of other malignancies within recent 5 years; (9) preoperative neoadjuvant chemoradiotherapy; (10) unstable angina pectoris or myocardial infarction within recent 6 months; (11) continuous systemic use of hormones within recent 1 month; (12) combined with other surgeries (except appendectomy or cholecystectomy); (13) emergent surgery due to complications caused by gastric cancer (bleeding, perforation or obstruction); (14) FEV1 less than 50% of the predicted value; (15) conversion to laparotomy.

The following are the withdrawal criteria: (1) diagnosis of M1 during or after surgery, i.e., distant metastasis upon intraoperative exploration or postoperative pathology, or positive exfoliated cells in the abdominal cavity; (2) duodenum invasion of diagnosis of T4b during or after surgery; (3) incomplete D2 dissection or R0 resection owing to masses formed by regional LNs coalescing or vital vessel surrounding; (4) necessary additional surgery during operation; (5) serious perioperative complications (unable to tolerate surgery or anesthesia); (6) referring to emergent surgery due to condition changes judged by attending physicians; (7) voluntary withdrawal or discontinued treatment due to personal reasons at any stage; (8) treatment violates study protocol.

Following enrollment, surgery should be performed within 2 weeks (including day 14). In addition to routine preoperative management, peritumoral submucosal CNs injection is administered 1 day before surgery in CNs group and dual tracer group. Carbon nanoparticles suspension injection (Chongqing Lummy Pharmaceutical Co., Ltd.) is diluted into 25 mg/ml with saline and then injected using “sandwich method.” Briefly, approximately 0.5 ml saline is firstly injected into the submucosal layer for mucosal elevation. Then, 0.2 ml CNs is injected. Finally, 0.5 ml saline is injected again to prevent leakage of CNs. This injection is performed at both proximal and distal sides of tumor under gastroscopy.

After anesthesia, ICG (Dandong Yichuang Pharmaceutical Co., Ltd.) powder is diluted into 2.5 mg/ml with saline and then injected into subserosal layer using “hexa-site” method in the ICG group and dual tracer group [18]. Briefly, the injection is performed at 3 sites along the lesser curvature (first branch of left gastric artery, angular and first branch of right gastric artery). Similar injection was repeated along the greater curvature.

A near-infrared (NIR) fluorescence imaging system (PINPOINT, NOVADAQ, Mississauga, ON, Canada) is used to obtain near-infrared fluorescence imaging during surgery. It provides high-definition white light visual field, near-infrared fluorescence visual field, and ICG-specific SPY visual field as well as merged visual field. LN dissection in the ICG group and dual tracer group is performed under the fluorescent laparoscope.

The standard sequence of LN dissection is as follows: (1) total gastrectomy: No. 6 → No. 7, 9, 11p → No. 8a, 12a, 5 → No.1 → No. 4sb → No. 4sa, 11d → No.2; (2) distal subtotal gastrectomy: No. 6 → No. 7, 9, 11p → No. 3, 1 → No. 8a, 12a, 5 → No. 4sb. Selective dissection of No.10 LNs is performed when (1) the primary tumor is located in the middle/upper stomach and invaded a large extent, (2) preoperative radiology suggests splenic lymphadenopathy, (3) significant fluorescent signal of No. 10 LNs, and (4) black stained No. 10 LNs by CNs. Surgical area is routinely inspected for possible residual fluorescent LNs or black-stained LNs, and additional dissection will be performed if necessary. D2 + LN dissection will be performed if fluorescent or black-stained LNs (such as No. 10 or No. 14v) are observed outside D2 region.

The following information will be recorded: (1) pathological findings including histological type, distant metastasis and location, NIH risk grade, and degree of radical surgery (R0/R1/R2); (2) postoperative complications of which the severity is graded according to the Clavien-Dindo system and serious complication is defined as grade III or above; (3) lab parameters including blood routine test (hemoglobin, red blood cells count, white blood cells count, lymphocyte count, neutrophil count and percentage, platelets count, monocyte count, etc.) and blood biochemistry (albumin, prealbumin, total bilirubin, indirect bilirubin, direct bilirubin, AST, ALT, creatinine, urea nitrogen, total cholesterol, triglyceride, fasting blood glucose, potassium, sodium, chloride and calcium, etc.); (4) postoperative recovery including time to first ambulation, time to first ventilation, time to liquid diet, postoperative highest body temperature, time to gastric tube withdrawal, daily gastric juice drainage volume, time to abdominal drainage tube withdrawal, daily abdominal drainage tube drainage volume, blood transfusion volume from the surgery to discharge, and postoperative hospital stay.

Before discharge, various forms of health education such as dietary brochure and popular science lecture are provided to each participant to clarify the importance of regular follow-up visits. For patient who fails to visit on time for reexamination, telephone contact will be carried out to advise prompt reexamination. All participants will be followed-up every 3 months for the first 2 years and every 6 months since the third year (i.e., 1, 3, 6, 9, 12, 15, 18, 21, 24, 30, and 36 months) after discharge. Table 1 will be filled out at each visit. Tumor recurrence or metastasis and survival status of all participants will be assessed accordingly.

The members of the DMC (data monitoring committee) will be independent from the trial sponsor and trial personnel. A senior data statistician will serve as the chairman of the committee, and the rest will be composed of independent data statisticians and clinical scholars. The DMC will hold a Data Monitoring Reporting Meeting in February of each year during the conduct of the trial. In addition to members of DMC, clinical investigators, statisticians, and supporting assistants of the trial will participate in the meeting and provide reports. Data monitoring will be completed by comparing the original data to confirm the completion status of data collection.

The evaluation of adverse events and serious adverse events is based on Common Terminology Criteria for Adverse Events v3.0. The study director must report adverse events or serious adverse events to the study committee and the healthcare department of the province (city) according to relevant laws and regulations. Serious adverse events should also be reported to the head of the medical institutions and corresponding reporting procedures shall be completed in accordance with relevant provisions. Adverse events with emergency reporting obligation are as follows: (1) all patients who died during treatment or within 30 days from the last treatment day (regardless of causal relationship with the study protocol treatment) and (2) patients with unexpected grade 4 non-hematological toxicities. Adverse events with regular reporting obligations are as follows: (1) death causally related to treatment 31 days after the last treatment day, including death suspected to be related to treatment (including death caused by obvious primary disease); (2) expected grade 4 non-hematological toxicities; (3) unexpected grade 3 adverse events; (4) other major medical events such as adverse events considered by the trial team to have an potentially, permanent, and significant impact on patients’ offspring. Adverse events in items (2) to (4) above will be reported periodically if any definite or possible causal relationship to the study is identified.

Safety interim analysis and futility interim analysis will be conducted every 8 months, and analysis report will be submitted to the Efficacy and Safety Evaluation Committee. The specific contents of the report include the following: ineligible patients/potentially ineligible patients, reasons for end of treatment/discontinuation/study protocol, adverse events and serious adverse events, completion rate of laparoscopic surgery, proportion of conversion to laparotomy, enrolled protocol deviations, disease-free rate/disease-overall survival rate of all participants, etc. The Efficacy and Safety Evaluation Committee will review and discuss the report in accordance with the procedures documented in the Clinical Safety Information Management Guidelines and make written recommendations to the study director including whether to continue the enrollment of the study.

The protocol can be amended after discussion and adoption by the study committee meeting, provided that the amendment of the protocol will not cause medical or financial burden or additional risk to enrolled patients. Any changes to the protocol must be identified in writing and signed by the trial director. Significant changes require approval of Institutional Review Board. The updated protocol will be uploaded to the clinical trial registry and copied to clinical investigators.