For a study, researchers wanted to understand how effectively injecting indigo carmine into the arteries near rectal cancer increases the number of lymph nodes that can be removed. This was a retrospective, nonrandomized study by a team of specialists at a large hospital. Patients who had surgery to remove their rectal cancer between 2013 and 2019 were studied. The lymph nodes from their rectal cancer surgeries were stained with indigo carmine and examined outside the body. The study found stained specimens (with indigo carmine) had more retrieved lymph nodes than unstained specimens. A total of 189 patients were analyzed in the study, of which 108 (57.1%) were stained with indigo carmine. A mean of 19.8±6.1 lymph nodes was identified in stained samples compared to 16.0±4.9 without staining (P<0.001). Multivariable analysis showed that 3.2 additional lymph nodes were found in stained specimens (95% CI: 1.0 to 5.3; P=0.02). In stained specimens, the adequate lymph node count (≥12) was increased in univariable (odds ratio: 3.24, 95% CI: 1.13 to 10.65; P=0.03) but not in multivariable analysis. The study found that chemoradiotherapy reduced the number of lymph nodes by 2.5 (P=0.008). After staining, 95.0% of chemoradiotherapy patients had more than 12 lymph nodes retrieved. The median follow-up of patients was 24.2 months, with a local recurrence rate of 3.3%. The study was limited by its retrospective design and the nonrandomized allocation. Specimens of 189 patients were analyzed, of which 108 (57.1%) were stained with indigo carmine. A mean of 19.8 ± 6.1 lymph nodes was identified in stained samples compared to 16.0 ± 4.9 without staining (p < 0.001). Multivariable analysis showed that 3.2 additional lymph nodes were found in stained specimens (95% CI: 1.0 to 5.3; p = 0.02). In stained specimens, the adequate lymph node count (≥12) was increased in univariable (odds ratio: 3.24, 95% CI: 1.13 to 10.65; p = 0.03) but not in multivariable analysis. Indigo carmine injection had no effect on the number of positive lymph nodes or the nodal stage. Chemoradiotherapy reduced the lymph node count by 2.5 (p = 0.008). After staining, 95.0% of patients with chemoradiotherapy had ≥12 lymph nodes retrieved. The median follow-up of patients was 24.2 months, with a local recurrence rate of 3.3%.

Source: journals.lww.com/dcrjournal/Abstract/2022/08000/Advanced_Lymph_Node_Staging_With_Ex_Vivo.10.aspx