letrozole or fulvestrant

This entry refers to the use of either letrozole or fulvestrant, two distinct pharmaceutical agents used primarily in the treatment of hormone receptor–positive breast cancer. Letrozole is a nonsteroidal aromatase inhibitor that works by inhibiting the enzyme aromatase, thereby reducing estrogen synthesis and limiting estrogen-driven tumor growth. Fulvestrant is a selective estrogen receptor degrader (SERD) that binds to and accelerates degradation of the estrogen receptor, blocking its activity and downregulating its expression. Both drugs are indicated for postmenopausal women with advanced or metastatic hormone receptor–positive breast cancer, often after progression on prior endocrine therapy[6][7]. They may be used as monotherapy or in combination with other agents such as CDK4/6 inhibitors (e.g., palbociclib)[2][4][5]. The choice between these drugs depends on clinical context; both have demonstrated efficacy but act via different mechanisms.