title: What is the lifetime risk of developing cancer?: the effect of adjusting for multiple primaries.
abstract: BACKGROUND
  The 'lifetime risk' of cancer is generally estimated by combining current incidence rates with current all-cause mortality ('current probability' method) rather than by describing the experience of a birth cohort. As individuals may get more than one type of cancer, what is generally estimated is the average (mean) number of cancers over a lifetime. This is not the same as the probability of getting cancer.
  
  
  METHODS
  We describe a method for estimating lifetime risk that corrects for the inclusion of multiple primary cancers in the incidence rates routinely published by cancer registries. The new method applies cancer incidence rates to the estimated probability of being alive without a previous cancer. The new method is illustrated using data from the Scottish Cancer Registry and is compared with 'gold-standard' estimates that use (unpublished) data on first primaries.
  
  
  RESULTS
  The effect of this correction is to make the estimated 'lifetime risk' smaller. The new estimates are extremely similar to those obtained using incidence based on first primaries. The usual 'current probability' method considerably overestimates the lifetime risk of all cancers combined, although the correction for any single cancer site is minimal.
  
  
  CONCLUSIONS
  Estimation of the lifetime risk of cancer should either be based on first primaries or should use the new method.
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Bart's and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ, UK. p.sasieni@qmul.ac.uk
authors.forename: P D
authors.initials: PD
authors.lastname: Sasieni
authors.forename: J
authors.initials: J
authors.lastname: Shelton
authors.forename: N
authors.initials: N
authors.lastname: Ormiston-Smith
authors.forename: C S
authors.initials: CS
authors.lastname: Thomson
authors.forename: P B
authors.initials: PB
authors.lastname: Silcocks
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002423:Cause of Death; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology*; D009378:Neoplasms, Multiple Primary / Q000453:epidemiology*; D011336:Probability; D018570:Risk Assessment / Q000379:methods*; D012737:Sex Factors