title: Use of a decision aid including information on overdetection to support informed choice about breast cancer screening: a randomised controlled trial.
abstract: BACKGROUND
  Mammography screening can reduce breast cancer mortality. However, most women are unaware that inconsequential disease can also be detected by screening, leading to overdiagnosis and overtreatment. We aimed to investigate whether including information about overdetection of breast cancer in a decision aid would help women aged around 50 years to make an informed choice about breast screening.
  
  
  METHODS
  We did a community-based, parallel-group, randomised controlled trial in New South Wales, Australia, using a random cohort of women aged 48-50 years. Recruitment to the study was done by telephone; women were eligible if they had not had mammography in the past 2 years and did not have a personal or strong family history of breast cancer. With a computer program, we randomly assigned 879 participants to either the intervention decision aid (comprising evidence-based explanatory and quantitative information on overdetection, breast cancer mortality reduction, and false positives) or a control decision aid (including information on breast cancer mortality reduction and false positives). Participants and interviewers were masked to group assignment. The primary outcome was informed choice (defined as adequate knowledge and consistency between attitudes and screening intentions), which we assessed by telephone interview about 3 weeks after random allocation. The primary outcome was analysed in all women who completed the relevant follow-up interview questions fully. This trial is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12613001035718.
  
  
  RESULTS
  Between January, 2014, and July, 2014, 440 women were allocated to the intervention group and 439 were assigned to the control group. 21 women in the intervention group and 20 controls were lost to follow-up; a further ten women assigned to the intervention and 11 controls did not answer all questions on attitudes. Therefore, 409 women in the intervention group and 408 controls were analysed for the primary outcome. 99 (24%) of 409 women in the intervention group made an informed choice compared with 63 (15%) of 408 in the control group (difference 9%, 95% CI 3-14; p=0·0017). Compared with controls, more women in the intervention group met the threshold for adequate overall knowledge (122/419 [29%] vs 71/419 [17%]; difference 12%, 95% CI 6-18; p<0·0001), fewer women expressed positive attitudes towards screening (282/409 [69%] vs 340/408 [83%]; 14%, 9-20; p<0·0001), and fewer women intended to be screened (308/419 [74%] vs 363/419 [87%]; 13%, 8-19; p<0·0001). When conceptual knowledge alone was considered, 203 (50%) of 409 women in the intervention group made an informed choice compared with 79 (19%) of 408 in the control group (p<0·0001).
  
  
  CONCLUSIONS
  Information on overdetection of breast cancer provided within a decision aid increased the number of women making an informed choice about breast screening. Becoming better informed might mean women are less likely to choose screening.
  
  
  BACKGROUND
  Australian National Health and Medical Research Council.
authors.affiliation: Screening & Test Evaluation Program (STEP), The University of Sydney, Sydney, NSW 2006, Australia; Centre for Medical Psychology & Evidence-based Decision-making (CeMPED), The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Jolyn
authors.initials: J
authors.lastname: Hersch
authors.affiliation: Centre for Medical Psychology & Evidence-based Decision-making (CeMPED), The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Barratt
authors.affiliation: Screening & Test Evaluation Program (STEP), The University of Sydney, Sydney, NSW 2006, Australia; Centre for Medical Psychology & Evidence-based Decision-making (CeMPED), The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Jesse
authors.initials: J
authors.lastname: Jansen
authors.affiliation: Screening & Test Evaluation Program (STEP), The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Les
authors.initials: L
authors.lastname: Irwig
authors.affiliation: Centre for Medical Psychology & Evidence-based Decision-making (CeMPED), The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Kevin
authors.initials: K
authors.lastname: McGeechan
authors.affiliation: School of Public Health, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Gemma
authors.initials: G
authors.lastname: Jacklyn
authors.affiliation: Department of Health Sciences, University of Leicester; Leicester, UK.
authors.forename: Hazel
authors.initials: H
authors.lastname: Thornton
authors.affiliation: Centre for Medical Psychology & Evidence-based Decision-making (CeMPED), The University of Sydney, Sydney, NSW 2006, Australia; Central Clinical School, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Haryana
authors.initials: H
authors.lastname: Dhillon
authors.affiliation: Screening & Test Evaluation Program (STEP), The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Nehmat
authors.initials: N
authors.lastname: Houssami
authors.affiliation: Screening & Test Evaluation Program (STEP), The University of Sydney, Sydney, NSW 2006, Australia; Centre for Medical Psychology & Evidence-based Decision-making (CeMPED), The University of Sydney, Sydney, NSW 2006, Australia. Electronic address: kirsten.mccaffery@sydney.edu.au.
authors.forename: Kirsten
authors.initials: K
authors.lastname: McCaffery
mesh_terms: D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000517:prevention & control; D003657:Decision Making; D003661:Decision Support Techniques; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data*; D008875:Middle Aged; D010353:Patient Education as Topic; D010358:Patient Participation