Incidence trend and conditional survival estimates of gastroenteropancreatic neuroendocrine tumors: A large population-based study.

Given the rarity and indolent clinical course of gastroenteropancreatic neuroendocrine tumors (GEP-NETs), conditional survival might be the most suitable parameter for cancer survivors who wish to receive accurate prognostic information during follow-up. We have explored the updated incidence trend and the conditional survival of patients with GEP-NETs. Incidence trends from 2000 to 2014 were determined through an assessment of patients in the SEER cancer registry. Patients diagnosed between 1988 and 2011 were included in the conditional survival analysis, and the 3-year conditional cancer-specific survival (CCS3) was computed. The incidence of GEP-NETs, which is far higher than the incidence of many malignant tumors, is still increasing steadily (annual percentage change = 4.4). The risk of death from NETs is dynamic over time, and most deaths occur in the first 3 years after diagnosis. Patients with gastric, rectal, or appendiceal NETs hardly exhibit any excess mortality (CCS3 > 95%) given that they have already survived until a defined time-point within 10 years. The initial difference between each age group basically disappeared with an extension of the survival time since the initial diagnosis of gastric, appendiceal, or rectal NETs, but the difference persisted for tumors at other sites. Although patients with advanced-stage or higher-grade tumors have a worse survival at diagnosis than patients with early-stage or lower-grade tumors, the difference diminishes and might even disappear over time. For GEP-NETs that are rare but exhibit slow growth, clinically relevant variations in conditional survival were observed based on the time since diagnosis. Therefore, conditional survival can serve as a guideline that can be used by cancer survivors to plan their future and doctors to plan surveillance schedules.