The risk of lymph node metastasis in T1 colorectal cancer: new parameters to assess the degree of submucosal invasion

Purpose In T1 colorectal cancer, the depth is the main factor assessing the degree of submucosal invasion (DSI) to predict the risk of lymph node metastasis (LNM). The width (WSI) and the area of submucosal invasion (ASI) have been suggested as additional parameters to assess the risk of LNM. A review of the literature was undertaken on the correlation between WSI and ASI parameters and the incidence of LNM. Methods A Medline, PubMed, and Cochrane Library search was performed to retrieve all studies reporting correlation between WSI/ASI and risk of LNM in T1 colorectal cancer. Results Eight studies including 1727 patients were identified. All considered the degree of WSI and its influence on LNM: seven assessed different width cut-off of submucosal invasion, and one study the mean width of submucosal invasion in patients having or not involved lymph nodes. The WSI was significantly a prognostic factor for LNM (p < 0.05) in four studies. Both 2 and 3 mm seem to be the most discriminatory cut-off values of submucosal width invasion in defining the risk difference of LNM above and below the cut-off (2 mm, OR = infinite; 3 mm, OR = 6.9). Patients having a cut-off <= 5 mm of WSI showed a low risk (5.6%) of LNM rendering radical surgery unnecessary. Four studies assessed the risk of LNM according to the involved submucosal area (width x depth). In two of these, the ASI was a significant prognostic factor for LNM (p < 0.05). Conclusion The WSI and ASI seem to be reliable prognostic factors for LNM in T1 colorectal cancer. There is no agreement on ideal cut-off value.