Background and study aim: Population screening for colorectal cancer (CRC) is expected to increase the number
of pT1 CRCs. Local excision is an attractive treatment option, but is only oncologically
safe in the absence of lymph node metastasis (LNM). A systematic review of the predictive
value of pathological risk factors for LNM in pT1 CRC was conducted to provide data
for an evidence-based decision regarding follow-up or radical surgery after local
excision.
Methods: PubMed was searched for reports on predictors of LNM in pT1 CRC. Published papers
written in English and containing at least 50 patients were included. Meta-analyses
were performed using Review Manager 5.1.
Results: A total of 17 studies were included involving a total of 3621 patients with available
nodal status. The strongest independent predictors of LNM were lymphatic invasion
(relative risk [RR] 5.2, 95 % confidence interval [CI] 4.0 – 6.8), submucosal invasion
≥ 1 mm (RR 5.2, 95 %CI 1.8 – 15.4), budding (RR 5.1, 95 %CI 3.6 – 7.3), and poor histological
differentiation (RR 4.8, 95 %CI 3.3 – 6.9). Limitations of the study were: results
could not be stratified according to location in the colon or rectum; very early tumors
removed by polypectomy without surgical resection were not included in the meta-analysis;
and included studies were primarily from Asian countries and results therefore need
to be verified in Western populations.
Conclusion: The absence of lymphatic invasion, budding, submucosal invasion ≥ 1 mm, and poor histological
differentiation were each associated with low risk of LNM. Risk stratification models
integrating these factors need to be investigated further.