RESUMO
Breast cancer is the most common type of female cancer. Tamoxifen, a selective estrogen receptor modulator, is widely used to decrease breast cancer recurrence and mortality among patients. However, it also increases the risk of endometrial cancer. This study aimed to assess knowledge and decisional conflict regarding tamoxifen use. Between June and October 2014, breast cancer patients using tamoxifen were consecutively screened and requested to complete a survey including the EQ-5D, Satisfaction with Decision Scale (SWD), Decisional Conflict Scale (DCS), and a self-developed, 15-item questionnaire measuring tamoxifen-related knowledge. The study sample comprised 299 patients. The mean total knowledge score was 63.4 of a possible 100.0 (range, 13.3-93.3). While 73.9% of the participants knew that tamoxifen reduces the risk of breast cancer recurrence, only 57.9% knew that the drug increases endometrial cancer risk. A higher education level (≥ college) was associated with a higher, total knowledge score (ß = 4.291; P = 0.017). A higher knowledge score was associated with a decreased DCS score (ß = -0.366; P < 0.001). A higher SWD score was also associated with decreased decisional conflict (ß = -0.178; P < 0.001). In conclusion, the breast cancer patients with higher levels of tamoxifen-related knowledge showed lower levels of decisional conflict regarding tamoxifen use. Clinicians should provide the exact information about tamoxifen treatment to patients, based on knowledge assessment results, so as to aid patients' decision-making with minimal conflict.