Prognostic implications of occult nodal tumour cells in stage I and II colon cancer: The correlation between micrometastasis and disease recurrence.

INTRODUCTION: Occult nodal tumour cells should be categorised as micrometastasis (MMs) and isolated tumour cells (ITCs). A recent meta-analysis demonstrated that MMs, but not ITCs, are prognostic for disease recurrence in patients with stage I/II colon cancer.

AIMS & METHODS: The objective of this retrospective multicenter study was to correlate MMs and ITCs to characteristics of the primary tumour, and to determine their prognostic value in patients with stage I/II colon cancer.

RESULTS: One hundred ninety two patients were included in the study with a median follow up of 46 month (IQR 33-81 months). MMs were found in eight patients (4.2%), ITCs in 37 (19.3%) and occult tumour cells were absent in 147 patients (76.6%). Between these groups, tumour differentiation and venous or lymphatic invasion was equally distributed. Advanced stage (pT3/pT4) was found in 66.0% of patients without occult tumour cells (97/147), 72.9% of patients with ITCs (27/37), and 100% in patients with MMs (8/8), although this was a non-significant trend. Patients with MMs showed a significantly reduced 3 year-disease free survival compared to patients with ITCs or patients without occult tumour cells (75.0% versus 88.0% and 94.8%, respectively, p = 0.005). When adjusted for T-stage, MMs independently predicted recurrence of cancer (OR 7.6 95% CI 1.5-37.4, p = 0.012).

CONCLUSION: In this study, the incidence of MMs and ITCs in patients with stage I/II colon cancer was 4.2% and 19.3%, respectively. MMs were associated with an reduced 3 year disease free survival rate, but ITCs were not.