CPM knowledge is a 10-item multiple-choice measure developed by author Kirsten and Smith. Scores range from 0-100% correct with a higher score equaling more correct knowledge items. Items assessed understanding of the definition of CPM, surgical recovery time and risks/side effects, whether or not CPM improves survival, and whether CPM reduced the risk for disease progression. Will characterize the data using standard methods (estimated marginal means, standard errors, and Cohen's d effect sizes) separately by study arm. At follow-up scores will be reported as the difference between the knowledge score at two time points- the baseline knowledge score and follow-up knowledge score for both the CPM-DA arm and the UC arm.

Preparedness for the CPM decision was assessed using a 16-item scale adapted from the Ottawa Preparation for Decision Making scale modified to address the CPM decision. Items evaluated the amount of and satisfaction with information about CPM. Scores were reported as a mean across the items and ranged from 1-4 with 1 = Strongly Disagree; 2= Moderately Disagree; 3 = Moderately Agree; 4= Strongly Agree Higher scores = more prepared. Outcomes reported as estimated marginal means, standard errors, and effect size measures for usual care and B-Sure decision aid conditions.

The Ottawa Decisional Conflict scale has 16 items and five subscales: support for the decision, uncertainty about the decision, level of relevant information, clarity of relevant values, and effective decision. Items are rated on a 5-point Likert scale (0= Strongly Disagree to 4 = Strongly Agree). Scores for the five subscales were calculated by an average that was multiplied by 25, which is recommended by the scale's developers. Thus, scores can range from 0 (no decision conflict) to 100 (high decision conflict). Higher scores indicate more decisional conflict.

Self-efficacy was a 3-item measure of confidence in the ability to manage worries and uncertainty about a possible recurrence of breast cancer, concerns about future surveillance, and worries about undergoing future surveillance. Results reported as Estimated marginal means, standard errors, and effect size measures for usual care and B-Sure decision aid conditions. Scores were reported as the mean across the 3 items and ranged from 1 = Not at all confident; 2 = Somewhat confident; 3 = Moderately confident; 4 = Very confident; 5 = Extremely confident. Higher scores indicate more self-efficacy.

Worry is measured by a single item that asks how worried the participant is about having another form of breast cancer on a four-point Likert scale 1= not at all worried and 4 = very worried. Higher scores indicate more worry. Results reported as estimated marginal means, standard errors, and effect size measures for usual care and B-Sure decision aid conditions

Reasons for CPM were measured by an 11-item scale developed after a review of the qualitative and quantitative literature on motivations for CPM and interviews with women who chose or did not choose CPM. Scored were reported as a mean score across the 11 items. The scale was scored on a 1-4 scale from not at all important to Yes, extremely important and Higher score = more reasons/motivations. Outcomes reported as Estimated marginal means, standard errors, and effect size measures for usual care and B-Sure decision aid conditions

Perceived risk was measured by two items. One item assessed contralateral breast cancer risk risk after unilateral mastectomy and radiation. The second item assessed perceived risk for chest wall recurrence after CPM. The first item asked "Out of 100 women with early breast cancer are treated with a single mastectomy or lumpectomy and radiation, about how many will develop breast cancer in the "other breast" in the 5 years after treatment? ___ women out of 100". The second item assessed risk for chest wall recurrence after bilateral mastectomy using the same scale 2. "If 100 women with early breast cancer have both breasts removed, how many will have breast cancer come back in the chest wall area of the "other breast" in the five years after treatment?". Outcomes reported as Estimated marginal means and standard errors for usual care and B-Sure decision aid conditions of the # out of 100 that women reported.

The scale has 27 items and four subscales: usefulness, ease of use, ease of learning, and satisfaction. Scales ranged from 1-7 with 1 being not at all or strongly disagree up to 7 being definitely or strongly agree.

Results provided for B-sure intervention arm only as usual care did not view or evaluate B-sure.

Basic descriptive information will be gathered regarding the length of time modules are viewed. B-Sure use will be assessed by average time spent in B-Sure

Data reported is for participants in the B-Sure intervention arm only. The usual care participants did not receive the intervention.