HORMONAL THERAPY – Classes of hormonal agents
HORMONAL THERAPY – Classes of hormonal agents
Hormone treatments use the sex hormones produced by our bodies, or drugs that block them, to treat cancer. Not all cancers respond to hormone therapy. Doctors might use hormone therapy for people with cancers that are ‘hormone sensitive’ or ‘hormone dependent’. This means that the cancer needs the hormone to grow. Cancers that can be hormone sensitive are breast cancer, prostate cancer, and uterine or endometrial cancer.
Cancers that are hormone sensitive or hormone dependent need hormones to grow. So stopping the hormone reaching the cancer cells may either slow down or stop the growth of the cancer. Hormone therapies can work by either stopping hormones being made or preventing the hormone reaching the cancer cell. Hormone therapy may be used in several situations:
If you are not able to have surgery or radiation or can’t be cured by these treatments because the cancer has ready spread beyond the prostate gland.
If your cancer remains or comes back after treatment with surgery or radiation therapy
As an addition to radiation therapy as initial treatment if you are at high risk for cancer recurrence
Before surgery or radiation to try and shrink the cancer to make other treatments more effective.
MAJOR CLASSES OF HORMONAL AGENTS
Adrenocorticoids are used in the management of the acute lymphoblastic leukemia, chronic lymphoblastic leukemia, Hodgkin’s lymphoma, non-Hodgkin’s lymphoma and multiple myeloma. It may also be used to reduce edema in patients with primary or metastatic CNS tumors, to prevent allergic reaction or as an adjuvant analgesic for the pain associated with the bone metastasis.
Estrogens are the family of hormones that promote the development and maintenance of female sex characteristics, the menstrual cycle, and pregnancy. Estrogens are used in the management of patients with advanced prostate cancer. The effects of the estrogens are mediated by a direct action on prostatic tissue and through a suppression of LH secretion from the adrenal gland. One of the most commonly used estrogens in management of prostate cancer is diethylstilbestrol (DES). The administration of daily dose of 3 mg or more of the DES produces castration levels of testosterone within 7 to 21 days.
In addition, estrogens may be beneficial in the management of the small number of women with advanced stage breast cancer. The use of estrogen is generally limited to the postmenopausal women. The drug is started at dosed of 5 mg per day and escalated to doses of 15 to 25 mg/day based on the woman’s level of tolerance.
An antiestrogen is a substance that blocks the production or utilization of estrogens, or inhibiting estrogens effects. Antiestrogens may stop some cancer cells from growing and are used to prevent and treat breast cancer. Antiestrogens block the protein on the outside wall of the estrogen-sensitive breast cancer cell. By blocking the protein, known as the estrogen receptor, the free-floating estrogen cannot stimulate the cancer cells to grow and multiply any further. They are also being studied in the treatment of other types of cancer.
Commonly used antiestrogens are tamoxifen, raloxifene, toremifene, fulvestrant, and droloxifene. The drug tamoxifen is a common antiestrogen that has proven to have a positive effect in breast cancer patients for both treatment and prevention. The drug raloxifene is a newer antiestogen. Early research showed that raloxifene worked against breast cancer with fewer side effects than tamoxifene.
Use of tamoxifene has been associated with a number of side effects, including vaginal bleeding, menstrual irregularities, and hypercalcemia. Most women also experience hot flashes, mild nausea and fatigue while using the drug. Serious side effects include endometrial cancer and thromboembolism (blocking of a blood vessel by a particle of a blood clot at the site the blood clot formed)
Anti-androgens block the body’s ability to use any androgens. Anti-androgens are another class hormone therapy drugs that are used in prostate cancer treatment. Anti-androgens affect the receptors of the prostate cells nuclei and prevent the reception of testosterone. These anti-hormone drugs are sometimes used as monotherapy for prostate cancer patients who are in early stages with low risk tumor features. Anti-androgens work by blocking the testosterone receptors in the prostate cells.
Normally, testosterone would bind with these receptors and fuel the growth of prostate cancer cells. Some researchers believe that men with a higher number of hormone receptors will more quickly experience hormone refractory cancer, which occurs when the prostate cancer cells grow resistant to the hormone deprivation. With the receptors blocked, testosterone cannot “feed” the prostate. Anti-androgen therapy does not eliminate testosterone and therefore may have fewer or less severe side effects than those associated with surgical and medical castration. Drugs of this type, such as flutamide (elulexin), bicalutamide (casodex), cyproterone acetate (cyprostat) and nilutamide (nilandron), are taken daily as pills.
Progestins are compounds related to the steroid hormone progesterone. The most common progestins used in the management of the cancer include medroxyprogesterone acetate, hydroxyprogesterone caproate and megestrol acetate. The progestins are used in the management of the breast and endometrial cancer. Megestrol acetate is also used in the treatment of the ovarian cancer and medroxyprogesterone acetate is used in the treatment of the prostate cancer
Luteinizing Hormone-Releasing Hormone (LHRH) Agonists
Release of LHRH from the hypothalamus results in the secretions of LH and FSH from the pituitary gland, which in turn causes the secretion of estrogen from the ovaries and testosterone from the testes.
The LHRH agonists have been used in treatment of premenopausal and postmenopausal women with advanced breast cancer. LHRH analogs are injected or placed as small implants under the skin. Depending on the drug used, they are given anywhere from once a month up to once a year. Common LHRH analogs are leuprolide, nafarelin, goserelin, triptorelin, and histrelin.
Luteinizing Hormone-Releasing Hormone (LHRH) Antagonists
LHRH antagonists may be useful in the management of hormone-dependent cancers. These antagonists act on the same receptor sites as LHRH and cause the immediate inhibition of release of gonadotrophins and sex steroid hormone. This class of hormones may prove useful in the management of some cases of breast and prostate cancer. Common LHRH antagonists are Abarelix and Degarelix, quickly reduces testosterone levels. The most common side effects were problems at the injection site (pain, redness and swelling) and increased levels of liver enzymes on lab tests.