Antihormone therapy | |
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Specialty | endocrinology |
Antihormone therapy is a type of hormone therapy that suppresses selected hormones or their effects, in contrast with hormone replacement therapy, which encourages hormone activity.
The suppression of certain hormones can benefit patients with certain cancers because certain hormones prompt or help the growth of a tumor. [1] This is especially true in cancers relating to the sex organs. [2]
Hormones are made by glands and circulated through the bloodstream. [3] Hormones may act as a signal to cells to grow by attaching to them. [3] Antihormone therapy blocks hormones from sending these messages to cells. If a diagnostic test shows cancer in places with hormones attached, drugs may be prescribed to the patient to block the receptors and inhibit the growth of cancer cells. [3] Most antihormone therapies are administered by pill for 5 to 10 years after surgery. [4]
Hormone replacement therapy began in the 1960s but gained traction in the late 1990s. [5] Therapy methods have been developed rapidly since the 1970s, and survivorship of individuals with hormone receptor-positive cancer has skyrocketed. [6] In more recent years, since the 1990s, new classes of drugs have been released and greatly changed the way hormonal cancers, like prostate and breast cancer, are treated. [7] Research to understand how hormones influence the growth of cancer cells has prompted researchers to find new ways to use drugs to prevent and treat hormone receptor-positive cancer cells by limiting the production of sex hormones. [7] These methods of hormone suppression have opened the door for pioneering new cancer chemoprevention drugs. [7]
Tamoxifen is a SERM and is one of the most common and oldest forms of hormone therapy. [8] When breast cancer is found at an early stage or found to be Metastatic breast cancer, tamoxifen can be prescribed to selectively block estrogen's effect on certain cells. SERMs like tamoxifen attach to receptors on the cancer cells which blocks estrogen from attaching to the receptors. Tamoxifen is successful in lowering breast cancer reoccurrence rates, breast cancer occurrence in the opposite breast, and death from breast cancer in cases of hormone receptor-positive and hormone-sensitive cancer. [9] Tamoxifen is also thought to lower the risk of breast cancer in those who have a predisposition or at risk. [9] Tamoxifen may be used in pre and postmenopausal women. [10] Toremifene is a similar SERM drug to tamoxifen, but is less common and only approved for treatment of metastatic cancer. Toremifene is generally prescribed once tamoxifen is no longer effective. [11]
Fulvestrant is a SERD drug that acts by damaging and blocking estrogen receptors. [11] Fulvestrant is currently only approved by the FDA to treat cancer in postmenopausal women, but it is often prescribed off-label in combination with and LHRH agonist in premenopausal women to halt the functionality of the ovaries. [11] Fulvestrant is administered via injection in the buttocks. [11]
A group of drugs called aromatase inhibitors are commonly prescribed to postmenopausal women who test positive for hormone receptor-positive cancer. Aromatase in fat and muscle can circulate estrogen in postmenopausal women. [12] Aromatase in highly estrogen-sensitive tissues, such as the breast, uterus, vagina, bone, and blood vessels, provides estrogen locally, so aromatase inhibitors work by reducing this estrogen production. [12]
Ovarian suppression is known to slow the growth of hormone receptor-positive breast cancer in premenopausal women [13] and can also help preserve fertility during chemotherapy. [14] Ovarian suppression through drugs temporarily shuts down the ovaries preventing the production of oestrogen, thus slowing the rate of growth of hormone receptor-positive tumors. [14] Ovary suppression may also be achieved through surgical intervention known as an oophorectomy, which removes one or both ovaries sometimes in combination with the fallopian tubes. [15]
LHRH (luteinising hormone-releasing hormone) agonists block the production of sex hormones in both men and women. [16] In men, LHRH agonists seize testosterone production in the testicles, and in women it blocks the ovaries from producing estrogen and progesterone. [16] These drugs are most commonly used in treatments for prostate cancer. [16]
Side effects of antihormone therapy are generally minimal, but can produce similar feelings to menopause in women. [4] Common symptoms of all antihormone therapies include irregular menstrual cycles, hot flashes, weight gain, vaginal dryness, headaches, mood swings and hair thinning. [4] Less common but more serious drug-specific side effects include: [11]
Selective estrogen receptor modulators (SERMs), also known as estrogen receptor agonist/antagonists (ERAAs), are a class of drugs that act on estrogen receptors (ER). A characteristic that distinguishes these substances from pure ER agonists-antagonists is that their action is different in various tissues, allowing them to selectively inhibit or stimulate estrogen-like action in various tissues.
Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and men. It is also being studied for other types of cancer. It has been used for Albright syndrome. Tamoxifen is typically taken daily by mouth for five years for breast cancer.
Fulvestrant, sold under the brand name Faslodex among others, is an antiestrogenic medication used to treat hormone receptor (HR)-positive metastatic breast cancer in postmenopausal women with disease progression as well as HR-positive, HER2-negative advanced breast cancer in combination with abemaciclib or palbociclib in women with disease progression after endocrine therapy. It is given by injection into a muscle.
Fertility medications, also known as fertility drugs, are medications which enhance reproductive fertility. For women, fertility medication is used to stimulate follicle development of the ovary. There are very few fertility medication options available for men.
Aromatase inhibitors (AIs) are a class of drugs used in the treatment of breast cancer in postmenopausal women and in men, and gynecomastia in men. They may also be used off-label to reduce estrogen conversion when supplementing testosterone exogenously. They may also be used for chemoprevention in women at high risk for breast cancer.
Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors, which are members of the nuclear receptor family of intracellular receptors, and membrane estrogen receptors (mERs), which are mostly G protein-coupled receptors. This article refers to the former (ER).
Exemestane, sold under the brand name Aromasin among others, is a medication used to treat breast cancer. It is a member of the class of antiestrogens known as aromatase inhibitors. Some breast cancers require estrogen to grow. Those cancers have estrogen receptors (ERs), and are called ER-positive. They may also be called estrogen-responsive, hormonally-responsive, or hormone-receptor-positive. Aromatase is an enzyme that synthesizes estrogen. Aromatase inhibitors block the synthesis of estrogen. This lowers the estrogen level, and slows the growth of cancers.
Formestane, formerly sold under the brand name Lentaron among others, is a steroidal, selective aromatase inhibitor which is used in the treatment of estrogen receptor-positive breast cancer in postmenopausal women. The drug is not active orally, and was available only as an intramuscular depot injection. Formestane was not approved by the United States FDA and the injectable form that was used in Europe in the past has been withdrawn from the market. Formestane is an analogue of androstenedione.
Lasofoxifene, sold under the brand name Fablyn, is a nonsteroidal selective estrogen receptor modulator (SERM) which is marketed by Pfizer in Lithuania and Portugal for the prevention and treatment of osteoporosis and for the treatment of vaginal atrophy, and the result of an exclusive research collaboration with Ligand Pharmaceuticals (LGND). It also appears to have had a statistically significant effect of reducing breast cancer in women according to a study published in The Journal of the National Cancer Institute.
Hormonal therapy in oncology is hormone therapy for cancer and is one of the major modalities of medical oncology, others being cytotoxic chemotherapy and targeted therapy (biotherapeutics). It involves the manipulation of the endocrine system through exogenous or external administration of specific hormones, particularly steroid hormones, or drugs which inhibit the production or activity of such hormones. Because steroid hormones are powerful drivers of gene expression in certain cancer cells, changing the levels or activity of certain hormones can cause certain cancers to cease growing, or even undergo cell death. Surgical removal of endocrine organs, such as orchiectomy and oophorectomy can also be employed as a form of hormonal therapy.
Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or inhibiting or suppressing estrogen production. Antiestrogens are one of three types of sex hormone antagonists, the others being antiandrogens and antiprogestogens. Antiestrogens are commonly used to stop steroid hormones, estrogen, from binding to the estrogen receptors leading to the decrease of estrogen levels. Decreased levels of estrogen can lead to complications in sexual development. Antiandrogens are sex hormone antagonists which are able to lower the production and the effects that testosterone can have on female bodies.
A hormone-receptor-positive (HR+) tumor is a tumor which consists of cells that express receptors for certain hormones. The term most commonly refers to estrogen receptor positive tumors, but can also include progesterone receptor positive tumors. Estrogen-receptor-positive tumors depend on the presence of estrogen for ongoing proliferation.
An estrogen-dependent condition can be that relating to the differentiation in the steroid sex hormone that is associated with the female reproductive system and sex characteristics. These conditions can fall under the umbrella of hypoestrogenism, hyperestrogenim, or any sensitivity to the presence of estrogen in the body.
A selective estrogen receptor degrader or downregulator (SERD) is a type of drug which binds to the estrogen receptor (ER) and, in the process of doing so, causes the ER to be degraded and thus downregulated. They are used to treat estrogen receptor-sensitive or progesterone receptor-sensitive breast cancer, along with older classes of drugs like selective estrogen receptor modulators (SERMs) and aromatase inhibitors.
Ethamoxytriphetol is a synthetic nonsteroidal antiestrogen that was studied clinically in the late 1950s and early 1960s but was never marketed. MER-25 was first reported in 1958, and was the first antiestrogen to be discovered. It has been described as "essentially devoid of estrogenic activity" and as having "very low estrogenic activity in all species tested". However, some estrogenic effects in the uterus have been observed, so it is not a pure antiestrogen but is, instead, technically a selective estrogen receptor modulator (SERM). For all intents and purposes, it is a nearly pure antiestrogen, however.
Elacestrant, sold under the brand name Orserdu, is an anticancer medication which is used in the treatment of breast cancer. It is taken by mouth.
Estrogen deprivation therapy, also known as endocrine therapy, is a form of hormone therapy that is used in the treatment of breast cancer. Modalities include antiestrogens or estrogen blockers such as selective estrogen receptor modulators (SERMs) like tamoxifen, selective estrogen receptor degraders like fulvestrant, and aromatase inhibitors like anastrozole and ovariectomy.
Endoxifen, also known as 4-hydroxy-N-desmethyltamoxifen, is a nonsteroidal selective estrogen receptor modulator (SERM) of the triphenylethylene group as well as a protein kinase C (PKC) inhibitor. It is under development for the treatment of estrogen receptor-positive breast cancer and for the treatment of mania in bipolar disorder. It is taken by mouth.
A hormone-sensitive cancer, or hormone-dependent cancer, is a type of cancer that is dependent on a hormone for growth and/or survival. Examples include breast cancer, which is dependent on estrogens like estradiol, and prostate cancer, which is dependent on androgens like testosterone.
Endocrine therapy is a common treatment for estrogen receptor positive breast cancer. However, resistance to this therapy can develop, leading to relapse and progression of disease. This highlights the need for new strategies to combat this resistance.