Revised Staging Classification Improves Outcome Prediction for Small Intestinal Neuroendocrine Tumors

Small intestinal (SI) neuroendocrine tumors (NETs) have heterogeneous outcomes. The NET societies have recently proposed a TNM staging classification. In this study, we used population-based data to assess the validity of the staging system. We identified patients with SI-NETS diagnosed between 1988 and 2009 from the Surveillance, Epidemiology, and End Results registry. We used Kaplan-Meier analysis to assess disease-specific survival according to TNM status. Cox models were constructed to evaluate differences in prognosis after controlling for potential confounders. We identified 6,792 patients with SI-NET. Although the current staging system was predictive of prognosis, there was overlap among some groups (stage I/IIA, P = .36; stage IIB/IIIB, P = .70). Additionally, stage IIIB patients had better survival than stage IIIA patients (P < .001). Adjusted analyses showed similar outcomes for T1 versus T2 disease (hazard ratio [HR], 1.02; 95% CI, 0.63 to 1.66). Patients with T3 (HR, 3.60; 95% CI, 2.28 to 5.69) and T4 (HR, 5.50; 95% CI, 3.42 to 8.86) tumors had significantly worse survival than patients with T1 disease. N1 involvement conferred worse survival in T1 (HR, 3.08; 95% CI, 1.75 to 5.44) and T2 disease (HR, 2.73; 95% CI, 1.84 to 4.07) but not in T3 (HR, 0.99; 95% CI, 0.76 to 1.30) or T4 (HR, 0.98; 95% CI, 0.71 to 1.35) disease. A revised classification showed no overlap in survival across groups. Progressively more advanced T status is associated with worse SI-NET prognosis. Regional lymph node involvement is a marker of worse survival only among patients with T1 or T2 status. These results suggest that revisions to the current staging classification may be helpful.