The impact of the ratio of positive to total lymph nodes examined and outcome in colorectal cancer.

We sought to examine the significance of the number of nodes examined in node-positive colorectal cancer. Between January 1, 1994, and December 31, 2003, 7192 patients with colorectal cancer underwent potentially curative resection in Region 5 of the California Cancer Registry. Of these patients, 2636 patients were node-positive: 65.1 per cent were N1 and 34.9 per cent were N2. The median follow up was 39.5 months. The mean number of nodes examined was 10.4 (range, 1-89) for N0, 11.0 (range, 1-72) for N1, and 14.6 (range, 4-79) for N2 (P < 0.0001). N1 and N2 patients were stratified according to the percentage of positive nodes into quintiles (0.19 or less, 0.20 to 0.39, 0.40 to 0.59, 0.60 to 0.79, and 0.80 to 1.0). In both N1 and N2 disease, a lower percentage of lymph nodes involved with metastatic disease was associated with improved survival (P < 0.0001). The increasing ratio of positive to total nodes was the result of a decrease in the total number of nodes examined in N1 disease and a steeper decline in total nodes examined in relation to the increase in the number of positive nodes in N2 disease. The ratio of positive to total nodes has prognostic significance in node-positive colorectal cancer.