Cancer of unknown primary: a population-based analysis of temporal change and socioeconomic disparities

Background: Cancer of unknown primary (CUP) is the fourth most common cause of cancer death. With advanced diagnostics and treatments, we investigated the proportion of cancers diagnosed as CUP, treatment outcomes and association with socioeconomic disparities. Methods: We analysed trends in CUP diagnosis and outcome within the Surveillance, Epidemiology, and End Results registry between 1973 and 2008. Results: The percentage of all cancers diagnosed as CUP has decreased over time comprising