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Aromasin vs Femara - how do they compare?

Medically reviewed by Melisa Puckey, BPharm. Last updated on June 21, 2023.

How does Aromasin compare with Femara for breast cancer?

Official answer


How do Aromasin and Femara compare?

In a clinical trial called FATA-GIM3 that studied breast cancer treatment using Aromasin versus Femara (and also anastrozole) over a 5 year period, the conclusion was that neither of the treatments were superior in how well they worked. This study recommends that when choosing between these medications, the choice should be based on how well the patient can tolerate the medication, which medication they prefer and their ability to finance treatment.

Aromasin (exemestane) and Femara (letrozole) are both aromatase inhibitors (third generation) and are used to treat specific forms of breast cancer.

If breast cancer growth is increased by estrogen then the breast cancer is called estrogen dependent (or sometimes called ER-positive breast cancer). One way to help control estrogen dependent breast cancer growth is by reducing estrogen levels.

After menopause most of the estrogen in the body is made by an enzyme called aromatase which changes androgens into estrogen. Aromasin and Femara stop the aromatase enzyme working properly, which stops the estrogen being made and therefore reduces the risk of tumor progression after surgery.

Table of Comparison between Aromasin and Femara

Aromasin (exemestane) Femara (letrozole)
Medication type Aromatase inhibitors (third generation) Aromatase inhibitors (third generation)
What does it do? Lowers levels of estrogen Lowers levels of estrogen
Where does it works? Binds to the substrate-binding pocket of the aromatase enzyme Binds to the cytochrome P-450 component of the aromatase enzyme
What are the FDA approved uses? Adjuvant treatment ER-positive breast cancer in post-menopausal women.
Advanced breast cancer in postmenopausal women that has advanced using tamoxifen.
Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer.
Extended adjuvant treatment of early breast cancer in postmenopausal women, who have received 5 years of adjuvant tamoxifen therapy.
First line treatment in postmenopausal women with locally advanced or metastatic breast cancer.
Second-line treatment for advanced breast cancer that has progressed following antiestrogen therapy.
What are the off label uses? Reduce the risk of invasive breast cancer in ER-positive breast cancer in post-menopausal women. Recurrent ovarian (epithelial) cancer.
To increase fertility for women with polycystic ovary syndrome (PCOS) by inducing ovulation.
Form of medicine Tablets that you swallow Tablets that you swallow
Dose One tablet daily One tablet daily
Very common side effects
(10% or more)
Abdominal pain (up to 11%), decrease in white blood cells (20%), dizziness (10%), gynecological issues (10.5%), hair loss (15.1%), headache (13.%), high blood pressure (15.1%), high liver function tests (over 10%), hot flushes (up to 32.9%), joint pain (28.8 %), nausea (up to 18%), pain (13%), shortness of breath 10%, sleep problems (13.7%), sweating (17.8%), tiredness (up to 22.2%) Bone fracture (22%) cardiovascular disease (14%), other cardiovascular event (13%),constipation (11%) cough (13%), dizziness/lightheadedness (14%), headache (20%), high cholesterol (53%), hot flushing (50%), joint pain (25%), limb pain (10%), muscle pain (22%), nausea (17%), night sweats (15%), osteoporosis (15%), shortness of breath (18%), swelling of the the limbs (18%), sweating (24%), tiredness (34%), vaginal bleeding (13%), weight gain(13%)
Effectiveness 88.0% patients survival over 5 years 89.4% patients survival over 5 years


  • Aromasin and Femara are aromatase inhibitors (third generation) that are used to treat specific forms of breast cancer.
  • Aromasin and Femara showed similar effectiveness in the FATA-GIM3 clinical trial. Patient survival over 5 years was 88.0% for Aromasin and 89.4%.
  • Both Aromasin and Femara are oral tablets that are taken daily.

Related Questions


Aromasin medication information:

Femara medication information:

Adjuvant anastrozole versus exemestane versus letrozole, upfront or after 2 years of tamoxifen, in endocrine-sensitive breast cancer (FATA-GIM3): a randomised, phase 3 trial

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