From the Guidelines
The recommended treatment regimen for postmenopausal women with hormone receptor-positive breast cancer using Arimidex (anastrozole) is 1 mg taken orally once daily for 5 years. This aromatase inhibitor is typically prescribed for early-stage breast cancer, and for patients who have previously taken tamoxifen for 2-3 years, anastrozole may be continued to complete a total of 5 years of hormonal therapy 1. The medication should be taken at approximately the same time each day, with or without food. Patients should continue taking calcium and vitamin D supplements during treatment to help prevent bone loss, a common side effect of anastrozole, as recommended by the American Society of Clinical Oncology 1. Regular bone density scans are recommended to monitor for osteoporosis, especially in patients with a history of osteoporosis or severe bone loss, which is a relative contraindication for the use of anastrozole 1.
Key Considerations
- Anastrozole works by blocking the enzyme aromatase, which converts androgens to estrogens, thereby significantly reducing estrogen levels in postmenopausal women and preventing estrogen from stimulating the growth of hormone-dependent breast cancer cells 1.
- Common side effects include joint pain, hot flashes, fatigue, and mood changes, which should be discussed with a healthcare provider if they become bothersome 1.
- The decision to extend adjuvant endocrine therapy beyond 5 years should be made on a case-by-case basis, considering the individual patient's risk of recurrence and potential benefits and risks of extended therapy 1.
- Women with node-positive breast cancer should be offered extended AI therapy for up to a total of 10 years of adjuvant endocrine treatment, while women with low-risk node-negative tumors should not routinely be offered extended therapy 1.
Monitoring and Prevention
- Regular monitoring of bone density and potential side effects is crucial during anastrozole treatment 1.
- Patients should be informed of the possibility of joint stiffness, arthralgias, vasomotor symptoms, hypertension, dry eyes, and vaginal dryness while taking anastrozole 1.
- Clinicians should evaluate patients for baseline fracture risk and measure bone mineral density before initiating an aromatase inhibitor, and consider the use of bone-protective agents such as bisphosphonates and receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitors 1.
From the FDA Drug Label
DOSAGE & ADMINISTRATION 2. 1 Recommended Dose The dose of anastrozole tablet is one 1 mg tablet taken once a day. For patients with advanced breast cancer, anastrozole tablets should be continued until tumor progression. INDICATIONS & USAGE 1.1 Adjuvant Treatment Anastrozole tablets are indicated for adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer. INDICATIONS & USAGE 1.2 First-Line Treatment Anastrozole tablets are indicated for the first-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor unknown locally advanced or metastatic breast cancer.
The recommended treatment regimen for postmenopausal women with hormone receptor-positive breast cancer using Arimidex (anastrozole) is 1 mg tablet taken once a day. The treatment should be continued until tumor progression for patients with advanced breast cancer. Anastrozole is indicated for:
- Adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer.
- First-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor unknown locally advanced or metastatic breast cancer.
- Second-line treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy 2, 2.
From the Research
Treatment Regimen for Postmenopausal Women with Hormone Receptor-Positive Breast Cancer Using Arimidex (Anastrozole)
The recommended treatment regimen for postmenopausal women with hormone receptor-positive breast cancer using Arimidex (anastrozole) is as follows:
- Anastrozole is approved for use as an adjuvant treatment in postmenopausal women with early-stage, hormone receptor-positive breast cancer 3.
- The standard treatment duration is 5 years, which has been shown to be more efficacious in reducing breast cancer recurrence than 5 years of tamoxifen 3.
- Anastrozole can also be used as a continuing adjuvant treatment in women who have already had 2-3 years of adjuvant tamoxifen treatment for breast cancer 3.
- In patients with hormone receptor-positive tumors, switching to anastrozole after 2-3 years of tamoxifen treatment has been shown to be more effective than continued tamoxifen 4.
Efficacy and Safety of Anastrozole
The efficacy and safety of anastrozole have been established in several studies:
- Anastrozole has been shown to be at least as effective as tamoxifen in the treatment of postmenopausal women with advanced breast cancer, and to be more effective than tamoxifen in patients with estrogen receptor-positive disease 5, 6.
- Anastrozole is generally well tolerated, with the most common adverse events being gastrointestinal disturbances, headache, and hot flushes 5, 6.
- Anastrozole has been shown to have a survival advantage compared to megestrol in a combined analysis of patients enrolled in two phase III studies 5.
Sequential Hormonal Therapy
The use of sequential hormonal therapy for metastatic breast cancer after adjuvant tamoxifen or anastrozole has been studied:
- After recurrence or relapse on adjuvant endocrine therapy, responses to the sequential use of additional endocrine agents are common 7.
- For postmenopausal women, a wide choice of endocrine treatment options is available, and an optimal sequence has yet to be determined 7.
- Options for first-line therapy of metastatic disease include an AI for women who have received adjuvant tamoxifen or tamoxifen for patients who have received adjuvant anastrozole 7.