Survival in neuroendocrine neoplasms; A report from a large Norwegian population-based study.

Neuroendocrine neoplasms (NENs) are heterogeneous tumors originating from neuroendocrine cells. Their malignant potential varies from indolence to high-grade malignancy (carcinomas). We studied the survival of all NENs in Norway according to malignant potential and different primary sites. We identified all NEN cases diagnosed in 1993 to 2015 and reported to the national population-based Cancer Registry of Norway. We included 62 morphological types. According to morphological characteristics and known disease behavior, we stratified the tumors into two different groups: low/intermediate aggressiveness and high aggressiveness. A total of 17,128 NENs were analyzed. Median age was 67 years and 47.6% were females. The most common primary sites were in the lungs and the gastroenteropancreatic (GEP) system. The 5-year relative survival in patients with low/intermediate aggressive NENs was 64.8% (95% CI, 63.3-66.2) and high aggressive NENs 8.4% (95% CI, 7.8-9.1). Females had higher survival rates than males (p <0.001). The relative 5-year survival rate in patients younger than 50 years was 89.1% (95% CI, 87.4-90.7) vs 41.0% (95% CI, 34.9-46.9) in patients ≥80 years. In multivariable analysis gender, age at diagnosis, time of diagnosis, stage and primary sites were all predictors of outcome both in patients with low/intermediate tumors and high aggressive tumors. Survival improved significantly over time, regardless of sex, age and tumor stage.