title: Risk of ischemic heart disease in women after radiotherapy for breast cancer.
abstract: BACKGROUND
  Radiotherapy for breast cancer often involves some incidental exposure of the heart to ionizing radiation. The effect of this exposure on the subsequent risk of ischemic heart disease is uncertain.
  
  
  METHODS
  We conducted a population-based case-control study of major coronary events (i.e., myocardial infarction, coronary revascularization, or death from ischemic heart disease) in 2168 women who underwent radiotherapy for breast cancer between 1958 and 2001 in Sweden and Denmark; the study included 963 women with major coronary events and 1205 controls. Individual patient information was obtained from hospital records. For each woman, the mean radiation doses to the whole heart and to the left anterior descending coronary artery were estimated from her radiotherapy chart.
  
  
  RESULTS
  The overall average of the mean doses to the whole heart was 4.9 Gy (range, 0.03 to 27.72). Rates of major coronary events increased linearly with the mean dose to the heart by 7.4% per gray (95% confidence interval, 2.9 to 14.5; P<0.001), with no apparent threshold. The increase started within the first 5 years after radiotherapy and continued into the third decade after radiotherapy. The proportional increase in the rate of major coronary events per gray was similar in women with and women without cardiac risk factors at the time of radiotherapy.
  
  
  CONCLUSIONS
  Exposure of the heart to ionizing radiation during radiotherapy for breast cancer increases the subsequent rate of ischemic heart disease. The increase is proportional to the mean dose to the heart, begins within a few years after exposure, and continues for at least 20 years. Women with preexisting cardiac risk factors have greater absolute increases in risk from radiotherapy than other women. (Funded by Cancer Research UK and others.).
authors.affiliation: Clinical Trial Service Unit, University of Oxford, Oxford, United Kingdom. sarah.darby@ctsu.ox.ac.uk
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Darby
authors.forename: Marianne
authors.initials: M
authors.lastname: Ewertz
authors.forename: Paul
authors.initials: P
authors.lastname: McGale
authors.forename: Anna M
authors.initials: AM
authors.lastname: Bennet
authors.forename: Ulla
authors.initials: U
authors.lastname: Blom-Goldman
authors.forename: Dorthe
authors.initials: D
authors.lastname: Brønnum
authors.forename: Candace
authors.initials: C
authors.lastname: Correa
authors.forename: David
authors.initials: D
authors.lastname: Cutter
authors.forename: Giovanna
authors.initials: G
authors.lastname: Gagliardi
authors.forename: Bruna
authors.initials: B
authors.lastname: Gigante
authors.forename: Maj-Britt
authors.initials: MB
authors.lastname: Jensen
authors.forename: Andrew
authors.initials: A
authors.lastname: Nisbet
authors.forename: Richard
authors.initials: R
authors.lastname: Peto
authors.forename: Kazem
authors.initials: K
authors.lastname: Rahimi
authors.forename: Carolyn
authors.initials: C
authors.lastname: Taylor
authors.forename: Per
authors.initials: P
authors.lastname: Hall
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000150:complications / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D016022:Case-Control Studies; D017024:Chemotherapy, Adjuvant; D005260:Female; D006321:Heart / Q000528:radiation effects*; D006801:Humans; D008408:Mastectomy; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000209:etiology* / Q000401:mortality; D011832:Radiation Injuries / Q000209:etiology / Q000401:mortality; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant / Q000009:adverse effects*; D012306:Risk; D012307:Risk Factors