What is the use of Anastrozole (Arimidex)?

From the Guidelines

Anastrozole should be used to reduce the risk of invasive breast cancer in postmenopausal women at increased risk of developing breast cancer, at a dose of 1 mg/day orally for 5 years, as an alternative to tamoxifen, raloxifene, or exemestane. The use of anastrozole for breast cancer risk reduction is supported by the American Society of Clinical Oncology (ASCO) clinical practice guideline update 1. This guideline recommends discussing anastrozole as an option for postmenopausal women with a high risk of developing breast cancer, defined as a 5-year risk of at least 3% or a 10-year risk of at least 5% 1.

Key Considerations

• Anastrozole is not recommended for breast cancer risk reduction in premenopausal women 1.
• Clinicians should evaluate patients for baseline fracture risk and measure bone mineral density before initiating anastrozole, and consider the use of bone-protective agents such as bisphosphonates and receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitors 1.
• Patients should be informed of the possibility of joint stiffness, arthralgias, vasomotor symptoms, hypertension, dry eyes, and vaginal dryness while taking anastrozole 1.
• The medication should be taken at the same time each day with or without food, and patients should take calcium and vitamin D supplements to help maintain bone health while on anastrozole.

Benefits and Risks

• The benefits of anastrozole for breast cancer risk reduction include a reduced risk of invasive breast cancer, particularly in postmenopausal women with hormone receptor-positive breast cancer 1.
• The risks of anastrozole include decreased bone density, hot flashes, joint pain, weakness, and mood changes 1.
• The NSABP B-35 study found that anastrozole resulted in an overall statistically significant decrease in breast cancer-free interval events compared with tamoxifen, with a different toxicity profile 1.

Monitoring and Follow-up

• Regular bone density monitoring is recommended during treatment with anastrozole due to the increased risk of osteoporosis 1.
• Patients should be encouraged to exercise regularly and take adequate calcium and vitamin D supplements to help maintain bone health while on anastrozole 1.

From the FDA Drug Label

Anastrozole tablet is a prescription medicine used in women after menopause (“the change of life”) for: treatment of early breast cancer after surgery in women whose breast cancer is hormone receptor-positive the first treatment of breast cancer that has spread to nearby tissue or lymph nodes (locally advanced) or has spread to other parts of the body (metastatic), in women whose breast cancer is hormone receptor-positive or the hormone receptors are not known treatment of advanced breast cancer, if the cancer has grown, or the disease has spread after tamoxifen therapy.

The use of Anastrozole (Arimidex) is for the treatment of breast cancer in postmenopausal women, including:

• Early breast cancer after surgery in hormone receptor-positive women
• Locally advanced or metastatic breast cancer as first treatment in hormone receptor-positive women or women with unknown hormone receptors
• Advanced breast cancer after tamoxifen therapy 2

From the Research

Use of Anastrozole (Arimidex)

• Anastrozole is a nonsteroidal aromatase inhibitor used in the management of postmenopausal women with advanced breast cancer 3.
• It is indicated for the second-line endocrine treatment of postmenopausal women with advanced breast cancer 3.
• Anastrozole has been shown to be effective in reducing plasma estrogen levels, with maximal suppression achieved at dosages of 1 mg/day or higher 3.
• It has been compared to tamoxifen and megestrol acetate in clinical trials, with results showing similar clinical efficacy to megestrol acetate and a significant survival advantage over megestrol acetate 3, 4.
• Anastrozole has also been shown to be effective as a first-line therapy for advanced breast cancer in postmenopausal women, with a significant advantage over tamoxifen in terms of time to progression 5, 6.
• In addition to its use in advanced breast cancer, anastrozole is also approved for use as an adjuvant treatment in postmenopausal women with early-stage, hormone receptor-positive breast cancer 7.

Benefits and Tolerability

• Anastrozole has been shown to have a number of benefits, including a significant survival advantage over megestrol acetate and a lower incidence of thromboembolic events and vaginal bleeding compared to tamoxifen 3, 4, 5, 6.
• It is generally well tolerated, with the most common adverse events being gastrointestinal disturbances, headache, asthenia, and pain 3.
• Anastrozole has also been shown to have a favorable tolerability profile compared to tamoxifen, with fewer withdrawals due to drug-related adverse events 5, 6.

Clinical Applications

• Anastrozole is a valuable treatment option for postmenopausal women with hormone receptor-positive, early-stage breast cancer, with benefits including reduced risk of breast cancer recurrence and improved overall survival 7.
• It is also a reasonable alternative to tamoxifen for first-line endocrine therapy of advanced breast cancer, with a lower incidence of thromboembolic events and vaginal bleeding 4, 5, 6.