Neuroendocrine tumors in the stomach: An epidemiological analysis of Belgian Cancer Registry data 2010-2019

The prevalence of gastric NEN is estimated worldwide at 8.9% of all gastroenteropancreatic neuroendocrine neoplasm (GEP-NEN) and only 0.3%-1% of all gastric neoplasms, but is rising in the last decades. The aim of this project was to map the epidemiology of gastric neuroendocrine neoplasm (gNEN) in Belgium. This is a population-wide retrospective cohort study over 10 years (2010-2019), based on data from the Belgian Cancer Registry. A total of 641 patients were included; 605 patients with gNEN and 36 with MiNEN. The AAIR of gNEN was 0.67 per 100,000 person-years, increasing over the years and with a slight female predominance (55.4%). Neuroendocrine carcinoma (NEC) accounted for 15.7% (N = 95), with an AAIR of 0.11 per 100,000 person-years. The other 510 patients were diagnosed with gNET: G1 NET was most prevalent (54.3%) followed by G2 (32.5%) and G3 NET (3.5%). Concerning the clinical classification (type) of gNET, a diagnosis of type 1 tumors was presumed in 67.6%, type 3 tumors in 17.1% and type 2 tumors in 0.6% of patients. In only 3.8% of patients, the clinical classification was explicitly stated in the pathology report. Stage IV tumors were diagnosed in 13.4% (N = 81). A favorable evolution in pathology reporting is seen. Some variables-for example, clinical classification of gNET-were heavily underreported, stressing the importance of registries integrating clinical and pathological information.