The effect of preoperative endoscopic tattooing on lymph node retrieval in colorectal cancer: a systematic review and meta-analysis.

Purpose: The effect of preoperative endoscopic tattooing (ET) on accurate colorectal cancer localization and resection has been well established. However, its effect on lymph node (LN) retrieval remains unclear. The purpose of this study was to systematically compare LN retrieval between patients with colorectal cancer who underwent preoperative ET and those who did not.

Methods: A systematic search for relevant studies was conducted using the following databases: PubMed, Embase, and Web of Science. Studies that compared LN retrieval in patients with colorectal cancer with and without preoperative ET were included. Weighted pooled odds ratio (OR) and mean difference (MD) with the corresponding 95% confidence intervals (CIs) for all outcomes using the random-effects model were calculated.

Results: 10 studies, including 2231 patients with colorectal cancer were included. Six studies reported total LN yield and showed significantly higher LN yield in the tattooed group (MD:2.61; 95% CI:1.01-4.21, P=0.001). Seven studies reported the number of patients with adequate LN retrieval and showed a significantly higher number of patients with adequate LN retrieval in the tattooed group (OR:1.89, 95% CI:1.08-3.32, P=0.03). However, subgroup analysis revealed that both outcomes were only statistically significant in patients with rectal cancer, and not in patients with colon cancer.

Conclusions: Our results suggest that preoperative ET is associated with increased LN retrieval in patients with rectal cancer, but not in colon cancer. Further large-scale randomized control trials are necessary to validate our findings.