Systematic review and meta-analysis of histopathological predictive factors for lymph node metastasis in T1 colorectal cancer

In this study we examined whether histopathological findings, specifically lymphatic vessel invasion identified by an anti-human podoplanin antibody, and several other factors are associated with lymph node metastasis in T1 colorectal cancer. We searched PubMed and Cochrane Library, and also handsearched relevant journals, for reports written in English and published between 1998 and 2012, utilizing combination headings, such as 'colorectal cancer,' 'lymph node metastasis,' and 'risk factors.' For the report to be included in our study, the following criteria had to be met: (1) data on the frequency of lymph node metastasis in T1 colorectal cancer in relation to histopathological factors were reported; (2) patients had undergone bowel resection and had histologically diagnosed T1 colorectal cancer; (3) lymphatic vessel invasion was identified by immunohistochemistry with an anti-human podoplanin antibody rather than by hematoxylin and eosin staining; (4) univariate and multivariate analyses were conducted. Studies investigating molecular markers were excluded. The independent predictive factors were confirmed in at least one study included in the meta-analysis in the present systematic review. Microsoft Excel 2013 for Windows was used for the statistical analysis. Initially, 369 publications were identified in the database searches and handsearches, of which five ultimately met all of the inclusion criteria and selected for this systematic review. The meta-analysis revealed that only two factors were significantly associated with T1 colorectal cancer lymph node metastasis: (1) lymphatic vessel invasion identified by an anti-human podoplanin antibody [Mantel-Haenszel odds ratio (OR) 5.19; (95 % confidence interval (CI) 3.31-8.15; P = 0.01]; (2) tumor budding (OR 7.45; 95 % CI 4.27-13.02; P = 0.0077). Our meta-analysis revealed that lymphatic vessel invasion identified by an anti-human podoplanin antibody and tumor budding were significantly associated with T1 colorectal cancer lymph node metastasis.