Mesenteric Lymphadenectomy in Well-Differentiated Appendiceal Neuroendocrine Tumors.

BACKGROUND: Surgical resection is the primary therapy for local and locally advanced appendiceal neuroendocrine tumors. The role of mesenteric lymphadenectomy in these patients is undefined.

OBJECTIVE: The purpose of this study was to define the role and prognostic significance of mesenteric lymphadenectomy.

DESIGN: This was a retrospective, observational study.

SETTINGS: A population-based cohort from the National Cancer Institute Surveillance, Epidemiology, and End Results registry (January 1988 to November 2013) was used.

PATIENTS: Patients with well-differentiated neuroendocrine tumors and nonmixed histologies undergoing surgical resection were included.

MAIN OUTCOME MEASURES: The risk of lymph node metastases as a function of tumor size and overall survival with respect to lymph node count and tumor size was measured. Lymph node cut-point was determined using the Contal and O'Quigely method.

RESULTS: Of the 573 patients who met the inclusion criteria, 64% were women, 79% were white, and 76% were <60 years of age. Seventy percent of the tumors were ≤2 cm, and 77% were lymph node negative. Median lymph nodes retrieved were 0 (interquartile range, 0-14). The probability of nodal metastases was 2.7% in tumors ≤1.0 cm, 31.0% in tumors 1.1 to 2.0 cm, and 64.0% in tumors >2.0 cm. The probability of a positive lymph node increased with increasing lymph node count up to 26 lymph nodes. An ideal cut-point of 12 lymph nodes was identified by statistical modeling. After adjustment in the multivariable model, the group with 12 or fewer lymph nodes examined had significantly worse overall survival (HR = 4.33 (95% CI, 1.54-12.15); p = 0.005; 5-year survival, 88% versus 96%) than the group with more than 12 lymph nodes examined.

LIMITATIONS: Analysis was limited by the variables available in the database.

CONCLUSIONS: This is the largest study to date that looks at prognostic significance of lymph node count for well-differentiated appendiceal neuroendocrine tumors. Overall survival was worse where 12 or fewer lymph nodes were identified for tumors >1 cm. See Video Abstract at https://links.lww.com/DCR/A352.