Implications of sentinel lymph node mapping on nodal staging and prognosis in colorectal cancer

Abstract

Sentinel lymph node (SN) mapping for staging in colorectal cancer remains controversial and needs to be validated before it can be implemented in daily practice. We prospectively assessed the effect of SN mapping on nodal staging and its implication on survival in patients with colorectal cancer. Between November 2005 and July 2009, 331 patients underwent a resection for colorectal cancer. In 189 patients (group A) an ex-vivo SN procedure was performed with immunohistochemical analysis of the SN. Tumour cell deposits between 0.2 mm and 2.0 mm were referred to as micrometastases (pN1mi+). The remaining patients (n = 142, group B) had standard nodal staging. Multivariate Cox regression analysis was performed to identify prognostic factors for disease recurrence. The average number of harvested lymph nodes was higher in group A than in group B (15.5 ± 7.3 vs 12.1 ± 5.2, P < 0.0001). After conventional staging, 81 (43%) patients of group A were judged to have nodal metastasis. This increased to 89 (47%) patients when immunohistochemically detected micrometastases were included. In group B, 50 (35%) patients had nodal metastasis. During follow up, a lower recurrence rate was seen in N0 patients after SN mapping compared with the conventional staging group (4%vs 15.2%, P = 0.04). The SN procedure (hazard ratio = 4.1) was an independent predictor of disease recurrence. The SN procedure results in a more accurate staging of patients with colorectal cancer. This is reflected by a better prognosis of N0 patients after SN mapping.