Lymph node mapping with carbon nanoparticles and the risk factors of lymph node metastasis in gastric cancer

The study aimed to examine the applicability of carbon nanoparticles as a tracer for lymph node mapping and the related factors of lymph node and No.8p subgroup metastasis in patients with gastric cancer. Clinical data of 50 patients with gastric cancer, who had not received treatment preoperatively and underwent gastrectomy in Department of Gastrointestinal Surgery, Wuhan Union Hospital, between October 2014 and August 2015, were retrospectively analyzed. These patients were found to have no distant metastasis preoperatively. Thirty-five out of 50 patients were subjected to lymphatic mapping technique using carbon nanoparticles as the tracer, and the rest 15 cases did not experience the lymphatic mapping and served as controls. The sensitivity, specificity, false positive rate and false negative rate were calculated according to the number of lymph nodes, and the staining and metastasis condition of lymph nodes. The diagnostic value of carbon nanoparticles on metastatic lymph nodes was evaluated. The relationship between the metastasis of lymph nodes or subgroup No.8p lymph nodes and clinicopathologic features was analyzed by χ²-test or Fisher's exact test. All patients underwent D2 surgery (lymph node dissection including all the group 1 and group 2 nodes) plus the dissection of the subgroup No.8p lymph nodes. It was found that the average number of harvested lymph nodes in lymphatic mapping technique group (45.7±14.5) was greater than that in control group (39.2±11.7), but the difference was not significantly different (P=0.138>0.05). The success rate, the accuracy, sensitivity, specificity and false negative rate was 97%, 57%, 28%, 62% and 72% respectively. The metastasis of lymph nodes was correlated to the depth of cancer invasion (T stage) (P=0.004<0.05), and the metastasis of No.8p lymph nodes was correlated to the extent of lymph node involvement (N stage) (P=0.007<0.05). Six cases had lymph node metastasis in subgroup No.8p, and their TNM stages and clinical stages were as follows: T1N2M0 IIA, T3N3M0 IIIB, T4aN3M0 IIIC, T4aN3M0 IIIC, T4aN3M0 IIIC, and T4bN3M0 IIIC. In conclusion, our study indicated that carbon nanoparticles failed to show good selectivity for metastatic lymph nodes; the result of lymphatic mapping does not achieve a satisfactory performance; the incidence of lymph node metastasis may increase, accompanying with the increase of the depth of cancer invasion; No.8p lymph node metastasis tends to occur for gastric carcinoma patients with the extent of lymph node metastasis over N2 stage.