Evaluation of two evidence-based decision aids for female BRCA1/2 mutation carriers in Germany: study protocol for a randomised controlled parallel-group trial.

Background: Women with BRCA1/2 mutations have a higher risk of developing breast and ovarian cancer compared to women of the general population. Various preventive options are available to deal with the increased risk of developing cancer. These include intensified breast cancer screening and risk-reducing bilateral mastectomy and salpingo-oophorectomy. The choice of a preventive option can lead to increased decisional conflict. To support these women in their decision-making process, two evidence-based decision aids were developed in an upstream research process and adapted to the German healthcare context. These will be evaluated within a randomised controlled trial (RCT) in terms of their effects on decision-making, women's level of information and psychological outcome variables.

Methods: A sample of 310 women carrying BRCA1/2 mutations (A) without a history of cancer or (B) with a history of unilateral breast cancer who have received post-test genetic counselling will be enrolled. Upon study consent, women will be randomly assigned to either the intervention or the control group. All participants will receive standard care including a physician's letter summarising the counselling content. After baseline data collection (t0), the intervention group receives the respective decision aid while the control group receives standard care only. The primary outcome variable assessed at a 3-month follow-up (t1) is the change of extent in decisional conflict (measured with the Decisional Conflict Scale). Secondary outcome variables comprise the stage of decision-making, self-reported symptoms of anxiety, depression and stress due to the genetic test result, and knowledge regarding cancer risks and preventive options. At t1, the extent of preparation for decision-making and acceptability of the decision aids will also be examined. Another secondary outcome variable assessed at 6-month follow-up (t2) is the extent of decision regret.

Discussion: These will be the first decision aids available for BRCA1/2 mutation carriers in Germany to be evaluated regarding their effectiveness and acceptability in clinical use within an RCT. Subsequently, they are to be integrated into the care concept of the centres of the German Consortium for Hereditary Breast and Ovarian Cancer and the affiliated breast centres. TRIAL REGISTRATION {2A}: DRKS DRKS00015823 . Retrospectively registered on 14 June 2019.