Tamoxifen in the Management of Breast Cancer: A Case Presented in Multidisciplinary Session With ClinicalDiscussion and Decision-Making

Background: Selective estrogen receptor modulators (SERMs) have beenshown to reduce the risk of developing estrogen-positive breast cancer. Tamoxifen,a potent SERM, has been successfully administered as adjuvant therapy for breastcancer. However, uterine pathologic changes may develop due to the effect oftamoxifen as both an agonist and antagonist of estrogen on the uterus. Here, wediscuss a case of breast cancer treated with tamoxifen to clarify one of the mostimportant complications, namely, endometrial hyperplasia.Case Presentation: A ۵۱-year-old woman presented with left breast mass andaxillary lymphadenopathy. Mammography showed a ۲۶-mm spiculated massconsistent with invasive ductal carcinoma in core needle biopsy.Immunohistochemical analysis revealed that the tumor was ER- and PR-positive,HER۲-negative. Adjuvant chemotherapy was completed, and the patient wasreferred to undergo adjuvant radiotherapy (RT). After the completion of RT,treatment with tamoxifen was initiated at the recommended dose of ۲۰ mg/day.Questions: The questions are when to use tamoxifen as adjuvant therapy forbreast cancer, how to follow the patient treated with tamoxifen, and when todiscontinue tamoxifen therapy.Conclusion: Use of tamoxifen for at least ۵ years after diagnosis is a reasonableoption for the prevention of breast cancer or its recurrence in high-risk patients.. Forpremenopausal women taking tamoxifen, irregular vaginal bleeding should beevaluated by hysteroscopy or uterine ultrasonography, and, if the etiology remainsunclear, a biopsy should be done. There are no evidence-based recommendations foruterine malignancy screening in patients who take tamoxifen. Currentrecommendations are annual gynecologic examination and evaluation of anyabnormal vaginal bleeding.

Keywords:

Tamoxifen , adjuvant hormone therapy , breast cancer , abnormal uterine bleeding