Whole point of administering a SERM after breast cancer is to reduce risk of recurrence. Increased estrogen exposure is associated with increased risk of breast cancer (per FA 2019 p. 636). So you're looking for something that is an estrogen antagonist at the breast, which narrows it down to B and C right off the bat.
submitted by โpparalpha(93)
Tamoxifen
Mechanism: selective estrogen receptor modulator (SERM) that acts as an antagonist on the estrogen receptors of the breast and acts as an partial agonist on estrogen receptors in bone and uterus. Therefore, โ risk of endometrial cancer and โ Risk of uterine sarcoma
Uses: ER or PR positive tumors (breast)