Purpose: To compare knowledge of the risks/benefits of tamoxifen when presented as the sole alternative to chemoprevention versus as one of two alternatives.
Method: We conducted two studies testing a decision aid (DA) designed to inform women about breast cancer chemoprevention. Participants in both studies were at high risk for breast cancer. Study 1 occurred prior to the STAR trial results and thus only described the risks/benefits of tamoxifen. Following the STAR trial, which showed that raloxifene was equivalent to tamoxifen in decreasing the risk of invasive breast cancer (with a similar side effect profile), we conducted Study 2 using a second DA that described the risks/benefits of both tamoxifen and raloxifene. Study 2 also tested two approaches to reducing cognitive burden: 1) presenting risk/benefit data for tamoxifen and raloxifene in separate pictographs vs. collapsing them into one pictograph and 2) including a summary table of information. After reviewing the DA, participants in both studies answered the following question: “Who is more likely to experience (health condition: e.g. endometrial cancer): A person who took tamoxifen, a person who did not take tamoxifen, equally likely.”
Result: 623 women participated in Study 1 and 690 participated in Study 2. As shown below, women’s knowledge of the risks/benefits of tamoxifen was reduced when they learned about both tamoxifen and raloxifene. Percent answering each question correctly
| Only Tamoxifen (S1) | Tamoxifen + Raloxifene (S2) | |
| Endometrial cancer | 72.8 | 45.5 |
| Blood clotting | 70.8 | 71.6 |
| Cataracts | 68.4 | 68.6 |
| Hormonal symptoms | 70.0 | 67.3 |
| Bone fractures | 69.4 | 42.8 |
| Breast cancer | 81.0 | 73.2 |
Conclusion: The STAR trial showed that women at high risk of developing breast cancer now have a second drug they can use to reduce this risk. Unfortunately, inclusion of information about this second alternative reduces people’s ability to process all of the information relevant to their decision.