Lymphadenectomy in endometrioid uterine cancer staging - How many lymph nodes are enough? A study of 11,443 patients

BACKGROUND. The purpose of the current study was investigate the association between the number of lymph nodes examined and the probability of detecting at least a single lymph node involved by metastatic disease in patients with endometrioid corpus cancer. METHODS. Demographic, clinicopathologic, and surgical information were obtained from the National Cancer Institute between 1990 and 2001. A logistic regression model was used to investigate the relation between the number of lymph nodes identified and the probability of detecting at least a single positive lymph node. RESULTS. Of 11,443 patients, the median age was 64 years (range, 22-74 years) In all, 78.7% had stage I disease, 10.3% had stage 11 disease, and 11.0% had stage III disease; 31.5% had grade 1 histology, 40.6% had grade 2 histology, and 24.3% had grade 3 histology. The median number of lymph nodes reported was 9 (range, 1-90 lymph nodes). The median number of lymph nodes and the percent of patients with positive lymph nodes have increased from 1988 to 2001. An increasing number of lymph nodes removed was associated with a higher likelihood of identifying those with lymph node metastases. Based on the logistic regression model, the largest increase in probability of detecting at least a single positive lymph node was observed when 21 to 25 lymph nodes were resected (odds ratio [OR] of 1.45; 95% confidence interval [95% CI], 1.08-1.94 [P <.01]). Removing greater than 25 lymph nodes did not improve the statistical probability (OR of 1.23; 95% CI, 0.94-1.61 [P =.131). CONCLUSIONS. The current study data suggest that the removal of 21 to 25 lymph nodes significantly increases the probability of detecting at least I positive lymph node in endometrioid uterine cancer. The definition of an adequate lymphadenectomy deserves further investigation.