From the Guidelines
The recommended duration of anastrozole for breast cancer after mastectomy is 2 years, as studies have shown that extending therapy to 5 years does not significantly improve disease-free survival or overall survival, while potentially increasing the risk of adverse effects, such as vaginal problems and musculoskeletal pain, as seen in the ABCSG 16 study 1.
Key Considerations
- The ABCSG 16 study found that anastrozole therapy for 2 years versus 5 years resulted in similar disease-free survival rates at 10 years, with 71.1% for 2 years and 70.3% for 5 years, and similar overall survival rates, with 85.3% for 2 years and 84.9% for 5 years 1.
- The study also found that the risk of second primary breast cancer, including contralateral recurrence, was not significantly different between the two groups, with a hazard ratio of 1.13 (0.74 to 1.73) for 5 years versus 2 years 1.
- Quality of life (QOL) was also assessed, with no significant difference in QOL between the two groups, although there was a slightly higher rate of vaginal problems and musculoskeletal pain in the 5-year group 1.
Treatment and Monitoring
- Anastrozole is typically taken as a 1 mg tablet once daily, and patients should be monitored regularly for potential side effects, such as joint pain, bone loss, hot flashes, and fatigue.
- Regular bone density monitoring is recommended during treatment, and calcium and vitamin D supplements are often prescribed concurrently to help maintain bone health.
- The decision to extend therapy beyond 2 years should be made after discussing the potential benefits versus side effects with your oncologist, taking into account individual patient factors and disease characteristics.
From the FDA Drug Label
For adjuvant treatment of early breast cancer in postmenopausal women, the optimal duration of therapy is unknown. In the ATAC trial, anastrozole was administered for five years [see Clinical Studies ( 14. 1)]. The optimal duration of anastrozole for breast cancer after mastectomy is unknown. However, in the ATAC trial, anastrozole was administered for five years 2.
From the Research
Duration of Anastrozole for Breast Cancer After Mastectomy
- The duration of anastrozole treatment for breast cancer after mastectomy can vary, but studies suggest that 5 years of treatment is a standard approach 3.
- Extending anastrozole treatment to 10 years may provide additional benefits in terms of disease-free survival (DFS) 4.
- A study found that continuing anastrozole for an additional 5 years after initial treatment with anastrozole or tamoxifen followed by anastrozole improved DFS and reduced the incidence of local recurrence and second primary cancers 4.
- Network meta-analysis suggests that 5-year letrozole and 10-year tamoxifen may be superior to anastrozole in terms of DFS and overall survival (OS) 5.
- Comparative reviews of anastrozole, letrozole, and exemestane suggest that these aromatase inhibitors have different efficacy and toxicity profiles, and may not be interchangeable in clinical practice 6.
Key Findings
- 5 years of anastrozole treatment is a standard approach for postmenopausal women with hormone receptor-positive breast cancer 3.
- Extending anastrozole treatment to 10 years may provide additional benefits in terms of DFS 4.
- Anastrozole is generally well-tolerated, but may be associated with an increased risk of bone fractures and other adverse events 3, 7.
Treatment Approaches
- Upfront strategy: anastrozole for 5 years versus tamoxifen for 5 years 6.
- Sequencial strategy: tamoxifen followed by anastrozole or the inverse for a total of 5 years 6.
- Switch strategy: delayed randomization after 2-3 years of tamoxifen, followed by anastrozole or the inverse for a total of 5 years 6.
- Extended strategy: delayed randomization after 5 years of tamoxifen, followed by anastrozole or placebo 6.