A case-control study of using carbon nanoparticles to trace decision-making lymph nodes around inferior mesenteric artery in rectal cancer.

Background: Accurate identification of lymph nodes localized around inferior mesenteric artery (IMA), with or without metastasis, is of crucial importance for surgeons when dissecting D2 or D3 lymph nodes in patients with rectal cancer (RC). The following study evaluates whether carbon nanoparticles can be used for detection of decision-making lymph nodes (DLNs) in station 253 lymph nodes found around IMA during RC surgery.

Methods: A total of 66 patients with rectal adenocarcinomas were recruited between January 2014 and August 2017. Patients were divided into carbon nanoparticle (CN) group and control (CL) group; for the CN group, 1 ml nanoparticles were endoscopically injected into submucosal layer of primary tumor 1 day before surgery. DLNs were defined as black-dyed nodes in CN group or macroscopic lymph nodes in CL group localized along the IMA, proximal to the origin of the left colic artery. D3 lymph nodes were dissected using laparoscopic radical resection, and then examined using pathological approach. Intra-operative and post-operative data were compared between the two groups.

Results: In CN group, black-dyed DLNs were easily found under laparoscopy; the median number of DLNs was 3 (range 1-9). In CL group, the median number of DLNs was 0 (range 0-3). Consistency between intra-operative DLNs and post-operative station 253 nodes were confirmed by pathological examination. Significant higher number of DLNs in station 253 nodes (2.91 ± 2.47 vs 0.58 ± 0.75, p < 0.001), number of station 251 nodes (12.85 ± 8.99 vs 8.09 ± 5.85, p = 0.014), number of station 253 nodes (5.21 ± 5.26 vs 3.15 ± 2.32, p = 0.045), and the number of total lymph nodes (24.06 ± 13.20 vs 16.21 ± 9.09, p = 0.007) were found in the CN group compared to CL group.

Conclusions: Carbon nanoparticles are useful for identifying DLNs in station 253 LNs around IMA in RC. It is not necessary to perform D3 lymph node dissection if there are no intra-operative DLNs metastases in RC.