How many lymph nodes are needed for an accurate pN classification in esophageal cancer? Evidence for a new threshold value.

The UICC recommends a number of at least six lymph nodes to be examined in the surgical therapy of esophageal cancer for a reliable pN classification. The aim of this study was to evaluate this threshold by means of the data from our patients.Following curative resection (R0) of esophageal cancer the numbers of examined tumor-free and tumor-involved lymph nodes were compared. Different statistical models of logistic regression were fitted to the data and checked for plausibility (Hosmer Lemeshow test). The sensitivity of a correct pN classification was then calculated and correlated to the total number of examined lymph nodes.A maximum increase of the sensitivity in classifying pN occurred from 0 to 6 examined lymph nodes. Nevertheless an additional improvement of sensitivity was continuously shown up to 100 examined nodes. An over 90% sensitivity of a correct lymph node classification was reached when more than twelve nodes were examined. Thus the results demonstrate in the case of esophageal cancer, that the suggestion by the UICC to examine at least 6 nodes for defining pN appears too low and may not represent the clinical situation. A ninety percent confidence level of a correct lymph node classification can be expected above 12 examined nodes similarly to the current recommended threshold in colorectal carcinoma.We suggest a new threshold for the number of examined lymph nodes of at least 12 instead of 6 nodes for accurately defining the pN category in esophageal cancer.