title: Aspirin intake and breast cancer survival - a nation-wide study using prospectively recorded data in Sweden.
abstract: BACKGROUND
  Aspirin (ASA) use has been associated with improved breast cancer survival in several prospective studies.
  
  
  METHODS
  We conducted a nested case-control study of ASA use after a breast cancer diagnosis among women using Swedish National Registries. We assessed prospectively recorded ASA exposure during several different time windows following cancer diagnosis using conditional logistic regression with breast cancer death as the main outcome. Within each six-month period of follow-up, we categorized dispensed ASA doses into three groups: 0, less than 1, and 1 or more daily doses.
  
  
  RESULTS
  We included 27,426 women diagnosed with breast cancer between 2005 and 2009; 1,661 died of breast cancer when followed until Dec 31, 2010. There was no association between ASA use and breast cancer death when exposure was assessed either shortly after diagnosis, or 3-12 months before the end of follow-up. Only during the period 0-6 months before the end of follow-up was ASA use at least daily compared with non-use associated with a decreased risk of breast cancer death: HR (95% CI) =0.69 (0.56-0.86). However, in the same time-frame, those using ASA less than daily had an increased risk of breast cancer death: HR (95% CI) =1.43 (1.09-1.87).
  
  
  CONCLUSIONS
  Contrary to other studies, we did not find that ASA use was associated with a lower risk of death from breast cancer, except when assessed short term with no delay to death/end of follow-up, which may reflect discontinuation of ASA during terminal illness.
authors.affiliation: Channing Division of Network Medicine, 181 Longwood Ave, Boston, MA 02115, US. michelle.holmes@channing.harvard.edu.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Holmes
authors.forename: Henrik
authors.initials: H
authors.lastname: Olsson
authors.forename: Yudi
authors.initials: Y
authors.lastname: Pawitan
authors.forename: Johanna
authors.initials: J
authors.lastname: Holm
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lundholm
authors.forename: Therese M-L
authors.initials: TM
authors.lastname: Andersson
authors.forename: Hans-Olov
authors.initials: HO
authors.lastname: Adami
authors.forename: Johan
authors.initials: J
authors.lastname: Askling
authors.forename: Karin Ekström
authors.initials: KE
authors.lastname: Smedby
mesh_terms: D001241:Aspirin / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000401:mortality* / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D011446:Prospective Studies; D012307:Risk Factors; D013548:Sweden
chemical_list: D001241:Aspirin