Improvement in TNM staging of pulmonary neuroendocrine tumors requires histology and regrouping of tumor size

Objective: Neuroendocrine tumors of the lung are currently staged with the 7th edition TNM non-small cell lung cancer staging system. This decision, based on data analysis without data on histology or disease-specific survival, makes its applicability limited. This study proposes a specific staging system for these tumors.Methods: We retrospectively analyzed 510 consecutive patients (female/male, 313/197; median age, 61 years; interquartile range, 51-70) undergoing lung resection for a primary neuroendocrine tumor between 2000 and 2015 in 8 centers. Multivariable analysis was performed using a Cox proportional hazard model to identify factors associated with disease-specific survival. A new staging system was proposed on the basis of the results of this analysis. Kaplan-Meier disease-specific survival was analyzed by stage using the proposed and the 7th TNM staging system.Results: Follow-up was completed in 490 of 510 patients at a median of 51 months (interquartile range, 18-99). Histology (G1-typical carcinoid vs G2-atypical carcinoid vs G3-large-cell neuroendocrine carcinoma) and pT were independently associated with survival, but pN was not. After regrouping histology and pT, we proposed the following staging system: IA (pT1-2G1), IB (pT3G1, pT1G2), IIA (pT4G1, pT2-3G2, pT1G3), IIB (pT4G2, pT2-3G3), and III (pT4G3). The 5-year survivals were 97.9%, 81.0%, 69.1%, 51.8%, and 0%, respectively. By using the 7th TNM, 5-year survivals were 95.0%, 92.3%, 67.7%, 70.9%, and 65.1% for stage IA, IB, IIA, IIB, and III, respectively.Conclusions: Incorporating histology and regrouping tumor stage create a unique neuroendocrine tumor staging system that seems to predict survival better than the 7th TNM classification.