Nodal positivity between <12 and >12 lymph nodes harvested in colorectal cancer undergoing SLNM compared with conventional surgery

Abstract

4048 Background: Sentinel Lymph Node Mapping (SLNM) upstages significantly more patients (pts) than conventional surgery (Conv Sx) in Colon Cancer (CCa). According to current guidelines, the examination of 12 or more LNs are required to ensure accurate staging. Our study compares the rates of nodal positivity between differing numbers of total Lymph Nodes (LNs) harvested to see if the nodal positivity of <12 LN harvested by SLNM is equivalent to >12 LN obtained by Conv Sx. Methods: Of 951 pts with CCa, 545 pts underwent SLNM and standard oncological resection; 406 pts received Conv Sx without SLNM. The total number of LNs harvested for each pt as well as number of pts with metastatic LNs were recorded. Pts were grouped according to 2–11 LNs, 12–25 LNs and >25 LNs. Results: Of 951 pts, 81 pts in SLNM group and 6 in Conv Sx group were excluded due to benign disease. Average (avg) total nodes harvested in 2–11 node group for SLNM and Conv Sx was 7.9 vs 6.8 nodes respectively. Overall nodal positivity for SLNM pts and Conv Sx pts in the 2–11 node groups was 48% vs. 33% (p=.02). In the 12–25 node group, avg total number of LNs harvested was 17.23 and 16.32 respectively. In the 12–25 node group, 53% of pts in the SLNM arm had +ve nodes vs 44% (p=0.17) in the Conv Sx group. In pts with >25 nodes harvested avg nodal positivity was 33.78% vs 32.38% for SLNM and Conv Sx. Overall nodal positivity was 55% for SLNM vs 37% for Conv Sx group. When SLNM pts with 2–11 LN harvested were compared to Conv Sx pts with 12–25 LN harvested, nodal positivity was 48% vs 44% (p=0.55). Conclusions: Increased survival has been shown when >12 nodes are harvested in CCa. On avg SLNM identified a higher number of total nodes than conventional surgery. In addition, SLNM pts had higher nodal positivity with <12 LNs harvested compared to the nodal positivity of >12 nodes harvested in the Conv Sx group. A higher number of LN harvested coupled with a greater nodal positivity with less LNs make SLNM a more accurate way to stage CCa. [Table: see text] No significant financial relationships to disclose.