Risk of lymph node metastasis in T1 carcinoma of the colon and rectum

Several recent reports of high local recurrence and lymph node metastasis in T1 carcinoma of the rectum prompted us to study the risk factors for lymph node metastasis in these lesions.

We reviewed the clinical records of 7,543 patients who underwent operative treatment for carcinoma of the colon and rectum from 1979 to 1995. Only patients with sessile T1 lesions who underwent colorectal resection were included in the study, yielding an analysis cohort of 353 patients. The following carcinoma-related variables were assessed: size, mucinous subtype, carcinomatous component, grade, site in colon and rectum, lymphovascular invasion, and depth of submucosal invasion. For the depth, the submucosa was divided into upper third (sm1), middle third (sm2), and lower third (sm3). Chi-squared tests and logistic regression were used to evaluate the variables as potential risk factors for lymph node metastasis.

The incidence of T1 lesions was 8.6 percent. In the analysis cohort, the lymph node metastasis rate was 13 percent. Significant predictors of lymph node metastasis both univariately and multivariately were sm3 (P = 0.001), lymphovascular invasion (P = 0.005), and lesions in the lower third of the rectum (P = 0.007). Poorly differentiated carcinoma was significant univariately (P = 0.001) but not in the multivariate model. No other parameter was associated with a significant risk.

T1 colorectal carcinomas with lymphovascular invasion, sm3 depth of invasion, and location in the lower third of the rectum have a high risk of lymph node metastasis. These lesions should have an oncologic resection. In a case of the lesion in the lower third of the rectum, local excision plus adjuvant chemoradiation may be an alternative.