Incidence and Prognostic Significance of Carcinoid Lymph Node Metastases

Background: Pulmonary carcinoid tumors are often considered indolent tumors. The prognostic significance of lymph node (LN) metastases and the need for mediastinal dissection is controversial. We sought to determine the incidence, risk factors, and prognosis of LN metastases in resected carcinoid patients. Methods: Patients undergoing lung resection for carcinoid and removal of ≥10 LNs were identified in the National Cancer Database from 2004 to 2014. Typical (TCs) and atypical carcinoids (ACs) were included. Clinical and pathologic LN status was assessed. Overall survival (OS) was analyzed using log-rank test and Cox hazard regression analysis. Results: A total of 3,335 patients (TC 2,893; AC 442), underwent resection (lobectomy/bilobectomy 84%, pneumonectomy 8%, sublobar resection 8%). LN involvement was present in 21% of patients (N1 15%, N2 6%) and increased with tumor size and AC histology. Tumor size was an independent predictor of LN disease. The rate of nodal upstaging was 13% (TC 11%, AC 24%). Independent predictors of OS were AC type (HR 3.25 [95% CI 2.19-4.78]) and LN metastases (HR 2.3 [1.49-3.58]). LN disease was associated with worse survival for TC > 2 cm (5-year OS 87% versus 94%, p = 0.005) and AC (58% versus 88%, p = 0.001), but not for small (≤ 2 cm) TC patients (5-year OS 93% versus 92%, p = 0.67). Conclusions: A substantial number of well-staged carcinoid patients had LN metastases. Large tumor size is a valuable predictor of carcinoid nodal disease. LN involvement was an independent predictor of worse survival. Nodal dissection in tumors > 2 cm and in atypical subtype can yield important prognostic information.