Breast cancer is a common diagnosis, often linked to hormones. For hormone-receptor-positive breast cancer, where estrogen fuels cancer cell growth, hormone therapy is a common treatment. Anastrozole and tamoxifen are two prominent medications used to disrupt estrogen’s influence on cancer cells.
Anastrozole: How It Works and Who Uses It
Anastrozole is a non-steroidal aromatase inhibitor (AI). It blocks the aromatase enzyme, which converts androgens into estrogen in body tissues. This significantly lowers estrogen levels. This reduction slows the growth of hormone-receptor-positive breast cancer cells. It is primarily prescribed for postmenopausal women with hormone-receptor-positive breast cancer, used as adjuvant therapy after surgery to prevent recurrence, and as a first-line treatment for advanced cancer.
Tamoxifen: How It Works and Who Uses It
Tamoxifen is a Selective Estrogen Receptor Modulator (SERM). Unlike anastrozole, tamoxifen does not reduce estrogen production; instead, it blocks estrogen receptors on breast cancer cells, preventing tumor growth. While blocking estrogen’s action in breast tissue, tamoxifen can act like estrogen in other parts of the body, such as bones and the uterus. It is prescribed for pre- and post-menopausal women, and sometimes men, with hormone-receptor-positive breast cancer. It treats early-stage and advanced cancer, and reduces invasive breast cancer risk in high-risk individuals.
Choosing Between Anastrozole and Tamoxifen
Choosing between anastrozole and tamoxifen depends on a patient’s menopausal status and cancer characteristics. Anastrozole is typically for postmenopausal women, as it inhibits estrogen production. Tamoxifen, by blocking estrogen receptors, suits pre- and post-menopausal women, and men, regardless of their estrogen production levels. Studies in postmenopausal women with advanced breast cancer show anastrozole is at least as effective, and sometimes superior, to tamoxifen in progression time and response rates. The decision also considers a patient’s overall health, other medical conditions, and individual cancer biology.
Common Side Effects and Their Management
Both anastrozole and tamoxifen can cause side effects. Common anastrozole side effects include joint pain, muscle aches, hot flashes, and fatigue. It can also lead to bone thinning, increasing osteoporosis and fracture risk. Bone density monitoring and supplements may be part of management.
Tamoxifen commonly causes hot flashes, night sweats, and vaginal dryness. More serious, though less frequent, side effects include an increased risk of blood clots and uterine cancer. Regular gynecological examinations are often recommended for women taking tamoxifen. Side effect management often involves lifestyle adjustments, supportive medications, and communication with healthcare providers.