title: Factors influencing the effect of age on prognosis in breast cancer: population based study.
abstract: OBJECTIVE
  To investigate whether young age at diagnosis is a negative prognostic factor in primary breast cancer and how stage of disease at diagnosis and treatment influences such an association.
  
  
  METHODS
  Retrospective cohort study based on a population based database of patients with breast cancer containing detailed information on tumour characteristics, treatment regimens, and survival.
  
  
  METHODS
  Denmark.
  
  
  METHODS
  10 356 women with primary breast cancer who were less than 50 years old at diagnosis.
  
  
  METHODS
  Relative risk of dying within the first 10 years after diagnosis according to age at diagnosis after adjustment for known prognostic factors and expected mortality.
  
  
  RESULTS
  Overall, young women with low risk disease who did not receive adjuvant treatment had a significantly increased risk of dying; risk increased with decreasing age at diagnosis (adjusted relative risk: 45-49 years (reference): 1; 40-44 years: 1.12 (95% confidence interval 0.89 to 1.40); 35-39 years: 1.40 (1.10 to 1.78); <35 years: 2.18 (1.64 to 2.89). However, no similar trend was seen in patients who received adjuvant cytotoxic treatment. The increased risk in younger women who did not receive adjuvant treatment compared with those who did remained when women were grouped according to presence of node negative disease and by tumour size.
  
  
  CONCLUSIONS
  The negative prognostic effect of young age is almost exclusively seen in women diagnosed with low risk disease who did not receive adjuvant cytotoxic treatment. These results suggest that young women with breast cancer, on the basis of age alone, should be regarded as high risk patients and be given adjuvant cytotoxic treatment.
authors.affiliation: Department of Epidemiology Research, Danish Epidemiology Science Centre, Statens Serum Institut, DK 2300 Copenhagen, Denmark.
authors.forename: N
authors.initials: N
authors.lastname: Kroman
authors.forename: M B
authors.initials: MB
authors.lastname: Jensen
authors.forename: J
authors.initials: J
authors.lastname: Wohlfahrt
authors.forename: H T
authors.initials: HT
authors.lastname: Mouridsen
authors.forename: P K
authors.initials: PK
authors.lastname: Andersen
authors.forename: M
authors.initials: M
authors.lastname: Melbye
mesh_terms: D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D001943:Breast Neoplasms / Q000188:drug therapy / Q000401:mortality* / Q000473:pathology; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies