A Three-decade Analysis of 3,911 Small Intestinal Neuroendocrine Tumors: the Rapid Pace of No Progress

Objectives: Small intestinal neuroendocrine tumors (SI-NETs) are the most common gastrointestinal neuroendocrine tumor, but their natural history and outcome remain poorly defined, which hinders both the prediction of disease progression and appropriate therapeutic options. We examined patterns, incidence, prognosis, and outcomes of these tumors over a 30-yr period.

Methods: Data were extracted from the NCI's SEER registry (1973-2002). Incidence rates, distribution, and 5-yr survival rates were analyzed and adjusted (U.S. decennial census data).

Results: Of the 18,641 NETs, 3,911 (21.0%) were SI-NETs, of which 1,953 (49.6%) were ileal. Since 1973, both SI-NET and its ileal variant have increased annually by 3.8% and 2.1%, respectively. Ileal tumors, as a percentage of SI tumors, have increased from 52% to 63.6%. The age-adjusted incidence of ileal, small intestinal, and digestive system NETs has increased 225%, 460%, and 720% over 30 yr. Ileal tumors have specifically increased in prevalence in white (274%) and black (500%) men and women (213% and 286%, respectively); an overall increase of fourfold in blacks and 2.4-fold in whites. Although 83.3% of SI-NETs were staged, 83.7% were histologically ungraded. Five-year survival rates for SI-NETs were 62.6 +/- 1% (all stages), 73.8% (localized), 72% (regional), and 43.2% (distant). These have not significantly altered since 1973 (P= 0.11).

Conclusions: SI-NETs have increased, particularly in men and in the black population, which may be due to in vivo changes, increased clinical and pathological awareness, or increased detection of tumors. SI-NETs are malignant, diagnosed late, and survival rates have remained unchanged over 30 yr.