title: Cancer of unknown primary: a population-based analysis of temporal change and socioeconomic disparities.
abstract: 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 <2% of cancers since 2007. A higher proportion of CUP was diagnosed in the elderly, females, blacks and residents of less affluent or less educated counties. Median survival of all CUP patients was 3 months, with no improvement over time. The 5-year survival significantly improved in those with squamous histology (squamous cell carcinoma; SCC) but only marginally in non-SCC. Factors associated with a longer survival on multivariate analysis included white race; female; <65 years old; most recent decade at diagnosis; SCC; married; a histological diagnosis; and treatment with radiotherapy (all P<0.001). Despite the improvement in survival with radiotherapy, its use was less frequent in females and blacks.
  
  
  CONCLUSIONS
  The percentage of cancers diagnosed as CUP is decreasing but prognosis remains poor, particularly in non-SCC CUP. However, significant socioeconomic disparities exist in diagnosis and survival, suggesting inequalities in access to diagnostic investigations and treatment.
authors.affiliation: Division of Cancer Medicine, Peter MacCallum Cancer Centre, Locked Bag No. 1, A'Beckett Street, East Melbourne, Victoria 3002, Australia. damien.urban@petermac.org
authors.forename: D
authors.initials: D
authors.lastname: Urban
authors.forename: A
authors.initials: A
authors.lastname: Rao
authors.forename: M
authors.initials: M
authors.lastname: Bressel
authors.forename: Y R
authors.initials: YR
authors.lastname: Lawrence
authors.forename: L
authors.initials: L
authors.lastname: Mileshkin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D054625:Healthcare Disparities; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009382:Neoplasms, Unknown Primary / Q000453:epidemiology / Q000208:ethnology / Q000401:mortality / Q000532:radiotherapy; D011379:Prognosis; D018426:SEER Program; D012959:Socioeconomic Factors; D015996:Survival Rate; D014481:United States / Q000453:epidemiology; D055815:Young Adult