8.5.3 Hormonal Therapy

Antiestrogens, or estrogen antagonists, are a group of medications used to block estrogen receptors. By blocking these receptors, cancer cells that require estrogen for growth are no longer able to undergo mitosis and cannot cause tumor development. These drugs are classified as hormonal therapies, as they block the influence of the hormone estrogen. They are primarily used for breast cancer; however, antiestrogens are only effective in breast cancers that are hormone-receptor positive. Tamoxifen and fulvestrant are two commonly used antiestrogens used for breast cancer. Tamoxifen is an oral medication that is given for approximately 5 years after breast cancer treatment. Fulvestrant, given intramuscularly, and elacestrant, a newer oral medication approved in 2023, are selective estrogen downregulators (SERD) that block estrogen receptors.

Aromatase Inhibitors

Aromatase inhibitors are another classification of hormonal therapy used to treat breast cancer in postmenopausal clients. Aromatase is an enzyme found in fatty tissue that converts hormones into estrogen. Aromatase inhibitors, including anastrozole and exemestane, stop the production of estrogen and thus the growth of estrogen receptor–positive tumors by blocking aromatase. These medications are taken daily as an oral tablet. Aromatase inhibitors may be prescribed for clients who are not good candidates for antiestrogens. Aromatase inhibitors may cause symptoms of menopause and muscle and joint pain, which may limit use if clients are not able to tolerate side effects. These drugs may also put clients at higher risk of osteoporosis (DailyMed, Anastrozole, 2023).

Antiandrogens

Antiandrogens, also known as androgen inhibitors or testosterone blockers, are hormonal therapies used to treat prostate cancer. These drugs block androgen receptors so that cancers that rely on testosterone and other hormones to grow cannot survive. These drugs may induce a reduction in masculine characteristics such as hair growth and erectile dysfunction. Drugs in this class include flutamide and bicalutamide. They are given by the oral route daily. Liver enzymes must be periodically evaluated during therapy, as these drugs are hepatotoxic.

Table 8.15 lists common hormonal therapies and typical routes and dosing for adult clients.

Adverse Effects and Contraindications

Tamoxifen citrate tablets are contraindicated in clients who require concomitant coumarin-type anticoagulant therapy or in clients with a history of deep-vein thrombosis or pulmonary embolus. Adverse effects of hormonal therapies include weight gain, fatigue, vaginal dryness, loss of interest in sex, hot flashes, osteoporosis, nausea, vomiting, and diarrhea. Male clients receiving hormonal treatment, such as for prostate cancer, may experience breast development and tenderness (DailyMed, Tamoxifen, 2022).

Table 8.16 is a drug prototype table for hormonal agents featuring tamoxifen. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Nursing Implications

The nurse should do the following for clients who are taking hormonal agents:

• Assess client overall well-being prior to administration, including vital signs, weight, fatigue, bone pain, and neurovascular status.
• Review laboratory values thoroughly, including complete blood counts, electrolyte profiles, serum creatinine, liver enzymes, and bone scans.
• Be aware of the drug’s black box warnings.
• Recognize and manage emergent situations such as hypersensitivity reactions.
• Assess for and provide supportive therapies as needed.
• Provide for educational, spiritual, and psychosocial needs of the client and caregivers.
• Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.