The impact of nano-carbon suspension lymph node tracing on rectal cancer surgery post-neoadjuvant therapy.

Background: To explore the impact of using nano-carbon suspension for lymph node tracing on the number of detected lymph nodes and short-term clinical outcomes in patients undergoing laparoscopic radical resection for rectal cancer following neoadjuvant therapy.

Methods: This study retrospectively analyzed clinical data from 109 patients who underwent neoadjuvant therapy and laparoscopic radical resection for rectal cancer at Weifang People's Hospital from January 2020 to December 2022. Of these, 43 patients received an endoscopic submucosal injection of nano-carbon suspension (experimental group), with 22 patients receiving the injection before neoadjuvant therapy and 21 patients receiving it 24 h before surgery. The remaining 66 patients did not receive the nano-carbon injection (control group). All patients received neoadjuvant therapy according to guidelines and were operated on by the same surgical team. By comparing the number of detected lymph nodes and short-term clinical outcomes among the three groups, the study aimed to investigate the impact of the endoscopic submucosal injection of nano-carbon and the timing of injection on the surgical quality for patients with rectal cancer undergoing neoadjuvant therapy.

Results: The number of detected lymph nodes in the groups injected with nano-carbon before neoadjuvant therapy and 24 h before surgery was significantly higher than that in the non-injected group (P = 0.000), with a significant increase in the proportion of detecting ≥ 12 lymph nodes (P = 0.016), showing statistical significance. There is no statistically significant difference in the number of detected lymph nodes between the group injected with nano-carbon before neoadjuvant therapy and the group injected 24 h before surgery (P = 0.141).

Conclusions: Endoscopic submucosal injection of nano-carbon suspension for lymph node tracing can increase the number of detected lymph nodes in rectal cancer surgery following neoadjuvant therapy, enabling more precise postoperative tumor staging. Although pre-neoadjuvant nano-carbon injection yielded a numerically higher lymph-node detection rate, this trend was not statistically significant (P = 0.141). Consequently, the optimal injection timing remains unconfirmed and should be validated in larger prospective studies.