Increased number of metastatic lymph nodes in adenocarcinoma of the ampulla of Vater as a prognostic factor: a proposal of new nodal classification.

Background. Although the number of metastatic lymph nodes in most gastrointestinal carcinomas is correlated inversely with prognosis, the prognostic value of the number of metastatic lymph nodes in ampullary adenocarcinoma has not been well characterized. Methods. Lymph node metastasis was assessed in the Surveillance, Epidemiology and End Results database in 1,057 ampullary adenocarcinomas that were operatively resected and for which at least 12 lymph nodes were examined. A complex pattern of survival versus extent of lymph node metastasis was captured by censored local regression. The impact of the extent of lymph nodes metastasis on survival was investigated by use of the K-adaptive partitioning algorithm to identify the most significant cut-of f points of metastatic lymph nodes affecting survival. Results. Two significant cut-off points points (0 and 2) for the metastatic lymph node segregated patients into 3 groups with clinically important differences in median survival: patients with no metastatic lymph node (477 cases) had a median survival of 91 months, patients with 1-2 metastatic lymph nodes (279 cases) had a median survival of 29 months, whereas patients with >= 3 metastatic Lymph nodes (301 cases) had a median survival of 19 months (P < .0001). These results were validated with additional single institution dataset (318 cases, P <.0001). Conclusion. The present results suggest that the nodal classification of ampullary adenocarcinoma should be categorized NO (no metastatic lymph node), N1 (1-2 metastatic lymph nodes), and N2 (>= 3 metastatic lymph nodes).