Objective To investigate the influence of different injection time of carbon nanoparticle tracer on the acquisition of lymph nodes in adenocarcinoma of esophagogastric junc-tion (AEG) treated by neoadjuvant chemoradiotherapy (nCRT) combined with surgical resection.

Methods The prospective randomized controlled study was conducted. The clinicopathological data of 120 AEG patients who were treated by nCRT combined with surgical resection in the Fourth Hospital of Hebei Medical University from March 2020 to March 2021 were selected. Based on random number table, patients were allocated into two groups. Patients undergoing endoscopic injection of carbon nanoparticle tracer 24 hours before nCRT were allocated into the experiment group, and patients undergoing endoscopic injection of carbon nanoparticle tracer 24 hours before surgical resection were allocated into the control group. All patients received the same plan of nCRT combined with D₂ radical gastrectomy. Observation indicators: (1) grouping situations of the enrolled patients; (2) surgical and postoperative pathological situations; (3) postoperative complications and treatment. Measurement data with normal distribution were represented as Mean±SD, and comparison between groups was analyzed using the independent sample t test. Measurement date with skewed distribution were represented as M(Q₁,Q₃), and comparison between groups was conducted using the Mann‑Whitney U test. Count data were described as absolute numbers, and comparison between groups was analyzed using the chi‑square test. Comparison of ordinal data was analyzed using the non‑parameter rank sum test.

Results (1) Grouping situations of the enrolled patients. A total of 120 patients were selected for eligibility. There were 85 males and 35 females, aged (60±9)years. There were 60 patients in the experiment group and 60 patients in the control group, respectively. (2) Surgical and postoperative pathological situations. Patients in the two groups underwent D₂ radical gastrectomy successfully, with R₀ resection. The number of lymph nodes harvest, the number of lymph nodes stained, the number of metastatic lymph nodes stained, the number of micro lymph nodes, the number of inferior mediastinal lymph nodes, the number of inferior mediastinal lymph nodes stained, cases in postoperative pathological stage N0, stage N1, stage N2, stage N3a were 40.6±13.9,20.1±7.7, 1.0(0,3.0), 8.1±2.8, 3.7±1.3, 2.0(1.0,2.0), 18, 13, 23, 6 in patients of the experiment group, respectively. The above indicators were 30.4±8.3, 12.7±3.5, 0(0,1.0), 6.2±2.0, 2.4±1.2, 1.0(0,1.0), 23, 21, 15, 1 in patients of the control group, respectively. There were significant differences in the above indicators between the two groups (t=-5.01, 6.85, Z=-3.78, t=-4.04, -5.57, Z=-5.48, -2.12, P<0.05). (3) Postoperative complications and treatment. There were 5 cases of the experiment group and 7 cases of the control group with postoperative complications, showing no significant difference between the two groups (χ²=0.37, P>0.05). The patients with postoperative complications were improved after symptomatic treatment.

Conclusion Compared with injection of carbon nanoparticle tracer 24 hours before surgical resection, injection of carbon nanoparticle tracer 24 hours before nCRT can improve the acquisition of lymph nodes in AEG treated by nCRT combined with surgical resection.