BACKGROUND: Neuroendocrine tumors of the lung are staged with the AJCC-TNM for non-small cell lung cancer. However, neuroendocrine tumors have a distinct clinical behavior with grade providing critical prognostic information. We aim to determine components of a tumor-specific staging system.

METHODS: We identified 12,415 out of 58,736 neuroendocrine patients with complete 8

RESULTS: Overall, 7,524 G1, 1,211 G2, and 3,680 G3 tumors were analyzed with no differences between the sets. Each grade was separately classified by AJCC-TNM with poor separation of the curves and clustered survival. Recursive partitioning identified grade as the most significant factor driving overall survival. Subsequent partitions identified nodal status then T-category as additional important factors -- consistent with results from Cox regression analysis (G2 HR=3.05[95%CI: 2.65-3.5]; G3 HR=9.03[8.22-9.92]). When grade was integrated with nodal status and T-category to approximate a tumor-specific staging system, distinct overall survival stratification occurs at each proposed stage.

CONCLUSIONS: Grade was the dominant driver of prognosis in patients with neuroendocrine tumors of the lung. Incorporation of grade with traditional TNM parameters better discriminates between stage categories compared to current AJCC staging. Future NETL staging systems should include histologic grade.