Antiandrogens (Cancer treatment)
Antiandrogens are a class of medications primarily used for the treatment of prostate cancer. They work by blocking the effects of androgens, hormones essential for the growth and survival of both healthy and cancerous prostate cells. Common antiandrogens include bicalutamide, enzalutamide, flutamide, and nilutamide, with newer second-generation options like enzalutamide and apalutamide becoming popular due to their effectiveness against resistant cancer cases. These drugs can be administered orally and are often used in conjunction with other treatments that lower overall androgen levels, such as luteinizing hormone-releasing hormone agonists.
While effective, antiandrogens may lead to side effects, including reduced fertility, gastrointestinal issues, and hormonal changes such as hot flashes. Long-term use can also contribute to conditions like osteoporosis. Each antiandrogen may present unique side effects; for instance, nilutamide can cause light sensitivity, while flutamide may lead to dizziness or severe headaches. Understanding these treatments is crucial for patients and caregivers navigating prostate cancer management.
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Antiandrogens (Cancer treatment)
ATC CODE: G03HA
DEFINITION: Antiandrogens are a class of drugs used to treat prostate cancer. They can cause tumor cell death by blocking the effect of androgens, which are hormones required for the development and survival of both normal and cancerous prostate cells. In August 2014, DynaMed listed four antiandrogen medications that are used in androgen deprivation therapy for prostate cancer: bicalutamide, enzalutamide, flutamide, and nilutamide.
Cancers treated: Prostate cancer
Subclasses of this group: Nonsteroidal antiandrogens and synthetic steroids
Delivery routes: Administered orally as either capsules or tablets, can be taken on an at-home basis
How these drugs work: Androgens are male hormones, which include testosterone, dehydroepiandrosterone, and dihydrotestosterone. Androgens bind to androgen receptors on the surface of prostate cells and turn on signaling pathways involved in cellular development and survival and normal prostate function. Most prostate cancers, however, are also dependent on androgen signaling. Therefore, without it, tumors may stop growing.
Nonsteroidal antiandrogens and synthetic steroids compete with natural androgens for binding sites on androgen receptors, thereby blocking the activity of the natural androgens. Synthetic steroids can also act on the hypothalamus in the brain to reduce the production of testosterone.
More recently developed treatments have been labeled second-generation antiandrogen drugs. These are often administered when certain cancers, such as prostate cancer, develop resistance to first-generation antiandrogens. These newer drugs work by placing the androgen receptor in a stronger bind. This method has the effect of more effectively blocking receptor-mediated signaling. Enzalutamide and apalutamide are two of the more prescribed second-generation drugs.
Although antiandrogens inhibit androgen activity, blood levels of testosterone and other androgens may still be high, which could promote cancer cell growth. Therefore, antiandrogens are commonly used in combination with other drugs that lower androgen levels, such as luteinizing hormone-releasing hormone agonists, which can stop testosterone production. Antiandrogens may also be combined with inhibitors of the 5-α reductase enzyme, which block the conversion of testosterone into dihydrotestosterone. Dihydrotestosterone is thought to be a more potent and active androgen than testosterone.
Side effects: Because antiandrogens affect the prostate, they may cause low sperm counts or reduce fertility. Other common side effects include diarrhea, hot flashes, liver toxicity, constipation, decreased appetite, nausea or vomiting, and flu-like symptoms. Long-term treatment may also cause osteoporosis, in which bones become weakened.
There are also some drug-specific side effects. For example, nilutamide can temporarily cause the eyes to become light sensitive and take longer to adjust to changes in light and dark settings. Flutamide is also associated with the rare side effects of dizziness, fainting, and severe headaches.
Bibliography
Bone and Cancer Foundation. Questions & Answers about Prostate Cancer, Bone Metastases, and Treatment-Related Osteoporosis. New York, BCF, 2010.
Jones, J. Stephen, and Eric A. Klein. Management of Prostate Cancer. 3d ed. New York, Humana, 2013.
"Flutamide." MedlinePlus, 21 Aug. 2014, medlineplus.gov/druginfo/meds/a697045.html. Accessed 19 June 2024.
"Hormone Therapy for Prostate Cancer." National Cancer Institute, 22 Feb. 2021, www.cancer.gov/types/prostate/prostate-hormone-therapy-fact-sheet. Accessed 19 June 2024.
Sellers, Alisha D. "What to Know about Anti-Androgens for Advanced Prostate Cancer." Healthline, 16 May 2022, www.healthline.com/health/advanced-prostate-cancer/anti-androgens. Accessed 19 June 2024.
Tewari, Ashutosh. Prostate Cancer: A Comprehensive Perspective. London, Springer, 2013.
Wassersug, Richard J., et al. Androgen Deprivation Therapy: An Essential Guide for Prostate Cancer Patients and Their Loved Ones. New York, Demos, 2014.