Knowledge of Potential Harms and Benefits of Tamoxifen among Women Considering Breast Cancer Preventive Therapy.

Tamoxifen reduces breast cancer incidence in women at increased risk, but may cause side effects. We examined women's knowledge of tamoxifen's potential harms and benefits, and the extent to which knowledge reflects subjective judgments of awareness and decision quality. After a hospital appointment, 408 (55.7%) women at increased risk of breast cancer completed a survey assessing objective knowledge about the potential benefit (risk reduction) and harms (endometrial cancer, thromboembolic events, and menopausal side effects) of tamoxifen, and subjective tamoxifen knowledge and decisional quality. Two hundred fifty-eight (63.2%) completed a 3-month follow-up survey. Sixteen percent (15.7%) of participants recognized the potential benefit and three major harms of using tamoxifen. These women were more likely to have degree-level education [vs. below degree level; OR, 2.24; 95% confidence interval (CI), 1.11-4.55] and good numeracy (vs. poor numeracy; OR, 5.91; 95% CI, 1.33-26.19). Tamoxifen uptake was higher in women who recognized all harms and benefits (vs. not recognizing; OR, 2.47; 95% CI, 0.94-6.54). Sixty-six percent (65.8%) of tamoxifen users were unaware of its potential benefit and harms. Most (87.1%) women reported feeling informed about tamoxifen, and subjective decisional quality was high [Mean (SD), 17.03 (1.87), out of 18]. Knowledge regarding the potential harms and benefit of tamoxifen is low in women considering prevention therapy, and they may need additional support to make informed decisions about tamoxifen preventive therapy.

Beliefs About Medication and Uptake of Preventive Therapy in Women at Increased Risk of Breast Cancer: Results From a Multicenter Prospective Study.

INTRODUCTION: Uptake of preventive therapies for breast cancer is low. We examined whether women at increased risk of breast cancer can be categorized into groups with similar medication beliefs, and whether belief group membership was prospectively associated with uptake of preventive therapy. PATIENTS AND METHODS: Women (n = 732) attending an appointment to discuss breast cancer risk were approached; 408 (55.7%) completed the Beliefs About Medicines and the Perceived Sensitivity to Medicines questionnaires. Uptake of tamoxifen at 3 months was reported in 258 (63.2%). The optimal number of belief groups were identified using latent profile analysis. RESULTS: Uptake of tamoxifen was 14.7% (38/258). One in 5 women (19.4%; 78/402) reported a strong need for tamoxifen. The model fit statistics supported a 2-group model. Both groups held weak beliefs about their need for tamoxifen for current and future health. Group 2 (38%; 154/406 of the sample) reported stronger concerns about tamoxifen and medicines in general, and stronger perceived sensitivity to the negative effects of medicines compared with group 1 (62%; 252/406). Women with low necessity and lower concerns (group 1) were more likely to initiate tamoxifen (18.3%; 33/180) than those with low necessity and higher concerns (group 2) (6.4%; 5/78). After adjusting for demographic and clinical factors, the odds ratio was 3.37 (95% confidence interval, 1.08-10.51; P = .036). CONCLUSION: Uptake of breast cancer preventive therapy was low. A subgroup of women reported low need for preventive therapy and strong medication concerns. These women were less likely to initiate tamoxifen. Medication beliefs are targets for supporting informed decision-making.