Trends in Incidence of Neuroendocrine Neoplasms in Norway: A Report of 16,075 Cases from 1993 through 2010.

Background: Epidemiological studies show an increasing trend in the incidence of neuroendocrine neoplasms (NENs). A significant number of NENs occur in less common primary sites, but they are often excluded from the population-based studies. We studied the incidence trends of all NENs in Norway according to different primary sites.

Materials And Methods: Our analyses were based on cancer cases diagnosed between 1993 and 2010 and reported to the national population-based Cancer Registry of Norway. A total of 65 morphological codes were identified as neuroendocrine and stratified into 3 different groups of aggressiveness: low, intermediate and high.

Results: We identified 16,075 NENs of which 49.5% were in women. The median age at diagnosis was 65 years. The most common primary sites were the lung (48.1%) and the gastroenteropancreatic system (18.0%). Stage at diagnosis was local in 40.4% of the cases, regional in 17.5% and distant in 42.1%. The stage distribution was stable throughout the study period. The age-standardized (European) incidence rate (per 100,000 person-years) increased from 13.3 in 1993 to 21.3 in 2010 with an estimated annual increase of 5.1% in women and 2.1% in men. The increase was most pronounced for tumors of intermediate aggressiveness from 3.3 in 1993 to 7.3 in 2010. The largest annual increases were estimated for the adrenal gland (8.8%), the pancreas (6.9%) and the lungs (6.1%).

Conclusion: The incidence of NENs increased. Most primary tumors were found in the lungs or in the gastroenteropancreatic system. The increase in the incidence differed according to the primary site, gender and tumor aggressiveness.