Letrozole is an oral hormonal therapy used in breast cancer. It belongs to a group of medicines called aromatase inhibitors and is one of the most widely prescribed treatments for hormone receptor-positive (HR+) breast cancer in women after menopause.
Who is Letrozole prescribed for?
Letrozole is approved for postmenopausal women with hormone receptor-positive breast cancer. Depending on the stage of the disease, your oncologist may prescribe it:
- After surgery (adjuvant treatment) to lower the chance of the cancer coming back
- As extended treatment after several years of tamoxifen
- As treatment for advanced or metastatic breast cancer
It is not generally used in women who have not been through menopause unless their oncologist has a specific reason and other treatment is given alongside it.
How does it work?
After menopause, most of the body's estrogen is made by an enzyme called aromatase. Hormone receptor-positive breast cancer cells use estrogen to grow. Letrozole blocks aromatase, lowering estrogen levels and slowing or stopping the growth of these cancer cells.
How is it usually taken?
Letrozole is a 2.5 mg tablet usually taken once a day, with or without food. Taking it at the same time each day makes it easier to remember. In the adjuvant setting, treatment commonly continues for several years. Your oncologist will decide how long you should take it.
Common side effects
Because Letrozole lowers estrogen, many side effects are similar to menopause symptoms:
- Hot flushes and sweating
- Joint and muscle aches or stiffness
- Tiredness
- Raised cholesterol
- Gradual thinning of the bones (osteoporosis) with long-term use
Your doctor may arrange bone density scans and blood tests during treatment. Tell your oncologist about any side effect that troubles you; many can be managed without stopping treatment.
Important safety points
- Do not take Letrozole during pregnancy or while breastfeeding
- Letrozole should not be taken together with tamoxifen or with medicines that contain estrogen, unless your oncologist advises it
- Tell your doctor about every other medicine and supplement you take
- Do not stop treatment because you feel well; the benefit depends on taking it for the full prescribed period
Questions to ask your oncologist
- How long will I take Letrozole?
- How will my bone health be monitored?
- Which side effects should I report straight away?