Lymph node examination as a predictor of long-term outcome in Dukes B colon cancer

Mortality from cancer recurrence in Dukes B patients is approximately 25-30%. Outcome in Dukes B patients improves in direct relation to the number of lymph nodes examined. Examining fewer lymph nodes risks understaging and also such patients are less likely to receive chemotherapy. The aim of this study was to assess the impact of the number of lymph nodes examined on recurrence and mortality in Dukes B colon cancers. A retrospective database was constructed of 328 consecutive patients who underwent resection for Dukes B colorectal cancer between January 1993 and December 2001 at Middlemore Hospital. Patients with incomplete data, previous colorectal cancer, or perioperative deaths were excluded as were cases of rectal cancer. Data for the remaining 216 patients was subjected to multivariate and logistic regression analysis with 'patient death' or 'cancer recurrence' (CRec5) within 5 years as endpoints. A graph was constructed depicting CRec5 as broken down by lymph node strata. Receiver operator characteristic (ROC) curves were constructed for mortality and CRec5. The mean number of lymph nodes examined was 16.0 (median 14; range 2-48). The mean number of lymph nodes examined in those who died within 5 years was 12.8 vs. 17.5 in those who remained alive (p = 0.0027). The mean number of lymph nodes examined in those with evidence of recurrence within 5 years was 11.8 vs. 17.1 in those without recurrence (p = 0.0007). Analysis at various lymph node strata showed a sharp and statistically significant drop in the recurrence rate after the 16the node mark. The ROC curve for CRec5 showed that examination of 12 lymph nodes provided maximum sensitivity (0.60) and specificity (0.64). Examination of more than 16 lymph nodes is associated with a significant reduction in cancer recurrence. This supports the current clinical practice of harvesting and analysing as many nodes as possible during surgical resection and pathological analysis.