Prognostic impact of lymphatic invasion of colorectal cancer: a single-center analysis of 1,616 patients over 24 years.

BACKGROUND The degree of lymph node metastasis represents an important prognostic factor for cancer. Lymphovascular invasion is a traditional tool for estimating the aggressiveness of colorectal cancer. AIM To determine correlations between lymphatic invasion and lymph node metastasis or disease stage, and clarify the prognostic impact of lymphatic invasion. PATIENTS AND METHODS Patients (N=1,616) who underwent curative resection of primary colorectal adenocarcinoma at the Kurume University Hospital were included. Lymphatic invasion was calculated as an average and the degree was also determined (Ly0-3). Clinicopathological factors including lymphatic invasion were assessed by uni- and multivariate analyses to determine factors affecting survival. Survival was compared between different degrees of lymphatic invasion and lymph node metastasis. RESULTS Lymphatic invasion was absent (Ly0) in 806 patients (50%), and lymph node metastasis was absent (N0) in 1,085 patients (67%). Ninety-one percent of N0 patients were Ly0-1, 72% of N1 were Ly0-1, and 54% of N2 were Ly2-3. All patients with stage 0 disease (100%) were Ly0, 95% of stage I were Ly0-1, 46% of stage II were Ly1-2, and 36% of stage III were Ly2-3. Five- and 10-year survival rates were 83% and 68% in Ly0, 73% and 56% in Ly1, 66% and 49% in Ly2, 63% and 48% in Ly3, 81% and 67% in N0, 69% and 57% in N1, and 60% and 52% in N2, respectively (p<0.0001 each). CONCLUSION Lymphatic invasion in colorectal cancer correlates well with the status of lymph node metastasis and disease stage, representing an independent prognostic factor after curative resection. Lymphatic invasion can be used for evaluating tumor aggressiveness and estimating patient survival, irrespective of the actual number of positive lymph nodes found.