From the Guidelines
Anastrozole is a sister drug to Letrozole, as both are non-steroidal aromatase inhibitors used primarily in the treatment of hormone receptor-positive breast cancer in postmenopausal women.
Key Points
- Anastrozole (brand name Arimidex) works through the same mechanism as Letrozole by inhibiting the aromatase enzyme, which converts androgens to estrogens, thereby reducing estrogen levels in the body 1.
- The typical dosage for Anastrozole is 1 mg taken orally once daily.
- Other aromatase inhibitors in the same class include Exemestane (Aromasin), though this is a steroidal aromatase inhibitor with a slightly different molecular structure 1.
- These medications are generally well-tolerated but can cause side effects such as joint pain, bone loss, hot flashes, and increased risk of osteoporosis.
- Patients taking these medications should have regular bone density monitoring and may need calcium and vitamin D supplements to maintain bone health.
- The choice between Letrozole and Anastrozole often depends on the specific patient profile, tolerance to side effects, and sometimes insurance coverage or availability.
Mechanism and Efficacy
According to the NCCN guidelines, the 3 AIs (anastrozole, letrozole, and exemestane) have shown similar efficacy in the second-line setting 1.
Side Effects and Monitoring
The NCCN task force report highlights the importance of monitoring bone health in patients taking AIs, as they can cause a rapid decline in circulating estrogen levels, leading to bone loss and increased fracture risk 1.
Patient Considerations
Ultimately, the decision between Letrozole and Anastrozole should be based on individual patient factors, including medical history, tolerance to side effects, and personal preferences.
From the Research
Sister Drugs to Letrozole
A sister drug to Letrozole, an aromatase inhibitor, is a drug that belongs to the same class of medications and has a similar mechanism of action. Some examples of sister drugs to Letrozole include:
- Anastrozole, as mentioned in the study 2, which compares the differences between anastrozole and letrozole, two non-steroidal aromatase inhibitors.
- Exemestane, a steroidal aromatase inhibitor, as discussed in the study 3, which focuses on its clinical use and side-effect profile.
Characteristics of Sister Drugs
These sister drugs have similar characteristics, including:
- Aromatase inhibition, which is the gold standard for treatment of early and advanced breast cancer in postmenopausal women suffering from an estrogen receptor-positive disease, as stated in the study 2.
- Non-steroidal or steroidal structure, with anastrozole and letrozole being non-steroidal, and exemestane being steroidal, as mentioned in the study 3.
- Similar efficacy compared to tamoxifen as initial therapy for early breast cancer, improving disease-free survival, as discussed in the study 2.
Clinical Use of Sister Drugs
The clinical use of these sister drugs includes:
- Treatment of postmenopausal women with breast cancer, as mentioned in the study 4, which introduces letrozole as a new non-steroidal aromatase inhibitor for this purpose.
- Adjuvant treatment of early breast cancer, as discussed in the study 5, which reviews the mode of action and main clinical trials done with anastrozole.
- Prevention of breast cancer in high-risk postmenopausal women, as mentioned in the study 6, which discusses the use of aromatase inhibitors for treatment and prevention of breast cancer.