Anastrozole vs Tamoxifen: A Comprehensive Comparison
Women with Breast Cancer tend to compare the effectiveness of Anastrozole and Tamoxifen for various reasons.
You may have been prescribed Anastrozole in the treatment of Breast Cancer by your doctor. But now, looking for alternative medicine with minimum side effects and better results.
Whatever your reasons for comparing Tamoxifen and Anastrozole, you have come to the right place.
This article will discuss the differences between Anastrozole vs Tamoxifen in detail so you can decide with your doctor what will work best for you.
Introduction to Tamoxifen and Anastrozole
Anastrozole and Tamoxifen treat hormone-receptor-positive Invasive Breast Cancer, like Ductal Carcinoma In Situ (DCIS).
Higher levels of female hormones like Estrogen are related to an increased risk of Breast Cancer. These medications both work by inhibiting this hormone.
Your doctor may recommend any one of them if you have gone through Menopause or you are still in your pre-menopausal era.
You may have heard of Arimidex, the best-known brand name for Anastrozole. Tamoxifen is available under the brand names Nolvadex and Soltamox.
The overview: Anastrozole vs Tamoxifen
| Anastrozole | Tamoxifen | |
|---|---|---|
| Dosage | 1 mg once daily | 20-40 mg daily |
| Administration time | Usually five years | Usually five to ten years |
| Recurrence rate | Low | Slightly higher |
| FDA-approval | Approved | Approved |
| Mechanism of action | Inhibits Aromatase enzyme | Blocks effects of Estrogen |
| Side effects | Aching or pain in the joints and muscles, hot flashes, depression, difficulty sleeping, constipation, etc. | Bone or tumor pain, hot flashes, depression, headache, constipation, etc. |
Potential side effects
Tamoxifen can have several side effects, such as increased bone or tumor pain, hot flashes, depression, headache, constipation, etc.
It may also cause severe side effects like developing other types of Cancer like liver Cancer and cataracts.
Anastrozole may cause similar side effects to Tamoxifen, like aching or pain in the joints and muscles, hot flashes, depression, difficulty sleeping, constipation, etc.
People may get blood clots and experience changes in their liver function.
Dosage
As per your condition, the doctor recommends you the dosage factors. They will suggest the number of doses you take each day and the time allowed between doses.
The US Food and Drug Administration has approved daily 1 mg of Anastrozole.
The FDA initially approved Tamoxifen in 1977. Soltamox (Tamoxifen Citrate) is approved for a dose of 20-40 milligrams in the following way:
- Metastatic Breast Cancer: 20-40 mg daily. For daily doses greater than 20 mg, administer it in divided doses (morning and evening)
- Adjuvant treatment of Breast Cancer, DCIS, reduction of Breast Cancer incidence in women at high risk: 20 mg per day
Mechanism of action
Anastrozole is a type-II Aromatase inhibitor. It is effective and non-steroidal.
This drug works by inhibiting the Aromatase enzyme involved in Estrogen synthesis.
Cancer cells require Estrogen to develop; by inhibiting the enzyme, Anastrozole stops the growth of cancer cells.
Consequently, this drug also helps reduce or stop the growth and spread of tumors to other body regions.
Tamoxifen is an anti-Estrogen agent. It blocks the effects of Estrogen on Breast Cancer cells, stopping them from growing.
This drug can also work as an effective chemo-preventive agent against Breast Cancer.
Administration time
Depending on your circumstances, Anastrozole should be taken for a specified period. It is typically prescribed for five years to patients receiving treatment for primary Breast Cancer.
You may also take this medication for five years if you are not diagnosed with Breast Cancer but anyone in your family had it. It will lower your risk of developing the disease.
However, in a trial by San Antonio Breast Cancer Symposium, Anastrozole for ten years showed significantly higher rates of disease-free survival (DFS).
Trivia: DFS is the amount of time a patient survives after finishing primary cancer therapy before developing any indications or symptoms of the disease.
Like Anastrozole, Tamoxifen dosage recommendations will also change depending on individual situations.
Tamoxifen is typically prescribed for five to ten years to patients receiving treatment for primary Breast Cancer.
Tamoxifen is typically taken for as long as it successfully controls locally advanced or secondary Breast Cancer.
Tamoxifen is often used for five years if you have a strong family history of breast cancer and want to lower your risk of acquiring it.
Recurrence rate
There is a possibility that Breast Cancer will recur even after initial treatment is finished and testing reveals no signs of the disease.
Recurrent Cancers typically develop within the first three years following treatment. However, it may also occur many years later, locally or in distant body organs.
A randomized trial with 2980 post-menopausal women with DCIS was conducted to determine the efficacy of these medicines.
The participants were administered 1mg of oral Anastrazole or 20 mg of oral Tamoxifen daily for five years.
The results of the trial showed no significant difference in overall recurrence, with 67 recurrences for Anastrozole and 77 for Tamoxifen.
Takeaway
Anastrozole and Tamoxifen are two drugs that are used to treat Breast Cancer. People often tend to compare these two FDA-approved drugs.
These drugs have similar side effects like hot flashes, depression, difficulty sleeping, constipation, etc. Sometimes, Tamoxifen may lead to the development of other types of Cancer.
These side effects also depend on the dosage that your doctor prescribes you. FDA has approved 1 mg of Anastrozole and 20-40 mg of Tamoxifen daily.
Usually, both drugs are given for five to ten years, depending on individual circumstances.
Frequently Asked Questions
Is Tamoxifen better than Anastrozole?
Your doctor will help you determine which medicine is better for you. Tamoxifen and Anastrozole are both FDA-approved drugs for the treatment of Breast Cancer. They both are efficient in the treatment and may be used consecutively or after another treatment has not worked effectively.
How is Anastrozole different from Tamoxifen?
Anastrozole is an Aromatase inhibitor, whereas Tamoxifen is an anti-Estrogen. Both drugs’ function is to reduce Estrogen, a risk factor for Breast Cancer. The side effects of these are similar, but the dosage differs. Moreover, the recurrence rate is slightly higher in Tamoxifen.
Does Anastrozole have fewer side effects than Tamoxifen?
Compared to Anastrozole, Tamoxifen considerably worsens vasomotor symptoms, bladder control, and gynecological symptoms, while Anastrozole-treated patients have significantly worsened musculoskeletal and vaginal symptoms.
Is it possible to have no side effects from Anastrozole?
Anastrozole may show some side effects after its administration. The side effects severity can range from mild to dangerous. You may have aching or pain in the joints and muscles, hot flashes, depression, difficulty sleeping, constipation, etc.
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