Number of lymph nodes examined and its impact on colorectal cancer staging.

The status of lymph nodes is the most important prognosticator in colorectal cancer patients. Patients with lymph node involvement have a lower survival rate and are candidates for adjuvant therapy. The purpose of our study was to determine the number of lymph nodes that needs to be examined to accurately detect nodal metastasis. We conducted a retrospective study of 151 patients who underwent colorectal cancer operation at Harbor-UCLA Medical Center. Data from the operative report and pathology report were collected and analyzed. Fourteen (33.3%) patients with five to nine nodes examined had positive nodes. Twenty-six (57.8%) patients with 10 to 14 nodes examined had positive nodes. Patients who had 10 to 14 nodes examined were significantly more likely to have positive lymph nodes (P = 0.03). Patients with advanced T stage had a significantly higher number of positive lymph nodes (78.1% in T4 vs 11.1% in T1, P < 0.0001). Patients with poorly differentiated cancer showed a trend toward a higher positive node rate. Tumor differentiation and T stage seem to correlate with higher nodal metastasis rate. A higher number of lymph nodes examined was associated with a higher nodal metastasis rate. Examination of at least 10 lymph nodes would increase the yield of positive lymph nodes and avoid under-staging of patients with colorectal cancer.