Fact sheet: epidemiology of CUP syndrome in Germany

This article provides an overview of the incidence and survival rates of cancer of unknown primary (CUP) patients in Germany based on epidemiological, i.e., residence-based, data fromthe state cancer registries. According to these data, around 10,500 people in Germany were diagnosed with CUP each year between 2010 and 2020. Morphologically, adenocarcinomas are the most common; in around 30% of cases, only nonspecific histologies are reported. In older people, the proportion of nonspecific morphologies increases to over 45%. Overall, the prognosis of CUP is poor, with relative 5-year survival rates of around 17%, although patients of younger age and those with squamous cell carcinoma have significantly higher survival rates. The declining rate of new cases in the years 2010-2020 is in line with international comparative values and, in addition to differences in the definition and coding of the clinical entity, is probably mainly due to the improved diagnostic possibilities for identifying the primary tumor.