What is the use of Anastrozole (Arimidex)?

From the Guidelines

Anastrozole is a highly effective medication for the treatment of breast cancer in postmenopausal women, particularly for hormone receptor-positive breast cancers, and should be considered as a first-line treatment option due to its ability to reduce estrogen levels in the body and prevent cancer recurrence. The standard dose of anastrozole is 1 mg taken orally once daily, and it is typically prescribed for 5-10 years as adjuvant therapy following primary treatment of breast cancer, or as first-line treatment for advanced breast cancer 1.

Mechanism of Action and Efficacy

Anastrozole works by blocking the enzyme aromatase, which converts androgens into estrogens, thereby reducing estrogen levels in the body. This is particularly effective for hormone receptor-positive breast cancers that depend on estrogen for growth. Studies have shown that anastrozole provides a comparable benefit as adjuvant treatment for postmenopausal women with hormone-receptor-positive DCIS, with a different toxicity profile 1.

Side Effects and Monitoring

Common side effects of anastrozole include hot flashes, joint pain, weakness, mood changes, and decreased bone density. Regular bone density monitoring is recommended during treatment due to the increased risk of osteoporosis 1. Patients should take calcium and vitamin D supplements to help maintain bone health while on anastrozole. The medication should be taken at approximately the same time each day, with or without food.

Treatment Duration and Adherence

It's essential to continue taking anastrozole for the full prescribed duration, even if symptoms improve, as premature discontinuation may reduce its effectiveness in preventing cancer recurrence. The NSABP B-35 study found that anastrozole treatment resulted in an overall statistically significant decrease in breast cancer-free interval events compared with tamoxifen, with a significant difference apparent after 5 years of follow-up 1.

Key Considerations

• Anastrozole is not active in the treatment of women with functioning ovaries and should not be used in women whose ovarian function cannot be reliably assessed owing to treatment-induced amenorrhea 1.
• The medication has a different side effect profile compared to tamoxifen, with more fractures, musculoskeletal events, hypercholesterolemia, and strokes reported with anastrozole, and more muscle spasms, gynecologic cancers and symptoms, vasomotor symptoms, and deep vein thromboses reported with tamoxifen 1.
• Patients should be closely monitored for adverse effects, and the medication should be adjusted or discontinued if necessary.

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.

Anastrozole is used for the treatment of breast cancer in postmenopausal women with hormone receptor-positive breast cancer.

• It is used for the treatment of early breast cancer after surgery.
• It is used for the treatment of advanced breast cancer that has grown or spread after tamoxifen therapy. 2

From the Research

Anastrozole Overview

• Anastrozole is a nonsteroidal aromatase inhibitor used in the treatment of breast cancer in postmenopausal women 3.
• It works by reducing plasma estrogen levels, with maximal suppression achieved at dosages of 1 mg/day or higher 3.

Clinical Efficacy

• Anastrozole has been shown to be effective in the treatment of advanced breast cancer, with similar clinical efficacy to megestrol acetate 3.
• In the adjuvant setting, anastrozole has been shown to reduce the risk of breast cancer recurrence and improve overall survival compared to tamoxifen 4, 5, 6.
• Anastrozole has also been shown to be effective in the neoadjuvant setting, with improved clinical response and breast-conserving surgery rates compared to tamoxifen 5.

Treatment Options

• Anastrozole is approved for use as an adjuvant treatment in postmenopausal women with early-stage, hormone receptor-positive breast cancer 4.
• It is also approved for use in the extended adjuvant setting, after 2-3 years of tamoxifen treatment 4, 6.
• Anastrozole can be used as a first-line treatment for hormone-sensitive advanced breast cancer in postmenopausal women 5, 7.

Safety and Tolerability

• Anastrozole is generally well tolerated, with common adverse events including gastrointestinal disturbances, headache, and hot flushes 3, 4.
• Anastrozole has been shown to increase the risk of bone fractures, particularly in the treatment period 4, 6.
• Patients receiving anastrozole should be monitored for changes in bone mineral density and cardiovascular disease risk factors and outcomes 6.