title: Variation in breast cancer counts using SEER and IARC multiple primary coding rules.
abstract: OBJECTIVE
  To determine breast cancer case counts, on a given data set, using both Surveillance, Epidemiology, and End Results (SEER) program and International Agency for Research on Cancer (IARC) multiple primary coding rules and to describe differences, if any, by age at diagnosis, histology, stage at diagnosis, laterality, and grade.
  
  
  METHODS
  SEER and IARC multiple primary coding rules were applied to a dataset provided by the North American Association of Central Cancer Registries. Only registries whose data met high quality data standards for the time period studied (1994-1998) and whose permission was obtained were included. Percentage differences were calculated using IARC counts as the base.
  
  
  RESULTS
  Using IARC multiple primary rules resulted in 2.4% fewer cases. Among females, the highest percent changes by category were: age group - 80-84 year-olds (3.4%); histology - inflammatory breast cancer (4.6%); stage - distant (3.1%); grade - well differentiated (3.0%). Among males, the highest percent changes by category were: age group - 80-84 year-olds (1.7%); histology - for intraductal and lobular breast carcinoma in combination (4.8%); stage - distant (3.0%); grade - well differentiated (1.8%). Overall differences were generally unaffected when examined by laterality.
  
  
  CONCLUSIONS
  Breast cancer case counts are dependent on the multiple primary coding rules used.
authors.affiliation: North American Association of Central Cancer Registries, 2021 West White Oaks Drive, Springfield, IL 62704, USA. jhotes@naaccr.org
authors.forename: Joellyn L
authors.initials: JL
authors.lastname: Hotes
authors.forename: Larry F
authors.initials: LF
authors.lastname: Ellison
authors.forename: Holly L
authors.initials: HL
authors.lastname: Howe
authors.forename: Ingrid
authors.initials: I
authors.lastname: Friesen
authors.forename: Betsy
authors.initials: B
authors.lastname: Kohler
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology*; D018567:Breast Neoplasms, Male / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D011159:Population Surveillance; D012042:Registries; D018426:SEER Program; D014481:United States / Q000453:epidemiology