Predicting lymph node metastases in rectal cancer

For properly selected rectal cancers, local excision is a sphincter-saving alternative to abdominoperineal resection. If histologic assessment of a locally excised tumor reveals ominous features, further treatment with radical resection or irradiation may be necessary to treat potential lymph node metastases.

We wished to determine which features, if any, were predictors of nodal metastases.

Nine histologic and morphologic features of 62 radically excised rectal cancers were reviewed to determine which factors, if any, were associated with nodal disease.

Using a chi-squared analysis, we found worsening differentiation (P = 0.0001), increasing depth of penetration (P = 0.026), a microtubular configuration of 20 percent or more (P = 0.023), and the presence of venous (P = 0.001) or perineural invasion (P = 0.002) to significantly influence nodal disease. Lymphatic invasion was witnessed too infrequently to determine significance but, when present, was associated with nodal metastases in every case. Exophytic tumor morphology, mitotic count, and tumor size were not significant predictors. An analysis of variables determined that, of all factors or combination of factors examined, Broder's classification was the strongest predictor of nodal disease.

If a rectal cancer is accessible and of small size to facilitate local excision, an in-depth histologic assessment is needed to determine if nodal metastases are likely on a statistical basis.