Purpose: Results of the few extant reports concerning the clinical significance of so-called "occult micrometastases" of lymph nodes of patients with Dukes A and B colorectal cancer have been variable. We examined the presumably negative nodes of a larger cohort of such patients who were enrolled in the National Surgical Adjuvant Breast and Bowel Project clinical trials R-01 and C-01 for the influence of what we preferably designate as nodal mini micrometastases on parameters of survival.
Methods: Mini micrometastases were detected by immunohistochemical staining of the original lymph node sections with anticytokeratin A1/A3 in a total of 241 Dukes A and B patients with rectal and 158 with colonic cancers. Their frequency, as well as that of nuclear and histologic grades, and an estimation of their relationship to relative risks were correlated with overall and recurrence-free survival by univariate and multivariate analyses.
Results: Nodal mini micrometastases were detected in 73 of 399 (18.3 percent) patients of this cohort. They failed to exhibit any significant relationship to overall or recurrence-free survival. No association between the assessments of tumor differentiation and mini micrometastases was found. Nuclear and histologic grades also failed to further discriminate overall or recurrence-free survival in patients with A or B stages of colonic or rectal cancers in this cohort.
Conclusion: The immunohistochemical demonstration of nodal mini micrometastases failed to discriminate high- and low-risk groups of patients with colorectal cancer who were designated as being node-negative after routine pathologic examination.