Prognostic value of the detection of lymph node micrometastases in colon cancer

Introduction and objectives A study is made of the clinical repercussions of occult metastases-micrometastases (MMs+)-or isolated tumour cells (ITCs+) in the lymph nodes of patients with stage IIA and IIB colon adenocarcinoma initially considered as corresponding to N0. Material and methods A retrospective study of 39 patients with stage IIA and IIB (T3-T4 N0 M0) colon adenocarcinoma, subjected to similar surgical and adjuvant chemotherapy treatment, with long and careful follow-up (minimum: 5 years, mean: 81.7 months) was performed on their previously resected lymph nodes, with the aid of new histological and immunohistochemical (cytokeratin) sections, in order to detect MMs or ITCs. Disease-free survival (DFS) and global survival (GS) in the two groups (patients with MMs+ or ITCs+ vs. patients without MMs or ITCs) were compared at 5 years based on the corresponding Kaplan-Meier survival curves, with the Breslow test. Results A total of 382 lymph nodes from the 39 patients (mean: 9.8; standard deviation: 6.09) were revised. MMs+ were detected in 2 cases and ITCs+ in 2 more cases on the Cytokeratin study. GS of the whole series at 5 years was 89.74% (35 patients alive) with a DFS at 5 years of 79.49% (31 patients free of disease), but the 2 cases with MMs+ were dead at 5 years, with high statistical differences between both groups (MMs+/MMs-) (p < 0.0001). When comparing the group of MMs+/ITCs+ patients and the group of MM-/ITCs- patients, the DFS and GS times at 5 years were higher in the MMs-/ITCs- group (p=0.0692 and p=0.006 respectively). Conclusions Although the incidence of MMs+ or ITCs+ in the examined lymph nodes was low, the presence of MMs is related to a dramatic reduction in GS and DFS at 5 years. We encourage a detailed histological study of lymph nodes resected in patients with deep penetrating colon tumours in order to assure a pN0 status.