Clinical value of nano‐carbon lymphatic tracer for regional lymph node dissections of rectal cancer after neoadjuvant chemoradiotherapy

Objectives Regional lymph node (LN) volume decreases after neoadjuvant therapy, requiring a tracer for more accurate detection. Nano‐carbon tracer is a third‐generation tracer with several advantages, but its use for LN detection after neoadjuvant chemoradiotherapy for middle and low rectal cancer remains unclear. Therefore, this study investigated the effects and safety of anoscope‐guided subrectal injections of nano‐carbon suspension in this patient population. Methods This study retrospectively reviewed the medical records of 45 patients with middle and low rectal cancer admitted to our institution from March 2019 to March 2022. All patients received preoperative neoadjuvant chemotherapy and radiotherapy and were divided into nano‐carbon injection (n = 23; anoscope‐guided injections of nano‐carbon suspension in the rectal submucosa 2 cm above the dentate line 24 h preoperatively) and control (n = 22; directly underwent surgery) groups. The LN detection and complication rates were compared between the groups. Results The total and mean numbers of LNs and small LNs and the number of patients with > 12 LNs were significantly higher in the nano‐carbon injection group than in the control group. The total number of positive LNs and LN metastasis did not differ between the groups, nor did the anastomotic leakage, bleeding, stenosis, and abscess occurrence rates. Conclusions Anoscope‐guided nano‐carbon lymphatic tracing increased the LN detection rate, caused less trauma, and resulted in fewer postoperative complications than the direct surgical procedure. Thus, it is an effective, safe, and practical method that may improve dissections and the postoperative pathological staging accuracy.