1. What is letrozole? 
2. How does letrozole work?
3. Who it’s suitable for
4. Side effects of letrozole
5. When letrozole is given
6. How long will I have to take it?
7. How it’s taken 
8. Taking letrozole with other drugs 

1. What is letrozole? 

Letrozole is a drug used to treat breast cancer in women who have gone through the menopause. 

You may also hear it called Femara, which is its best-known brand name. There are a number of other brands of letrozole, all of which contain the same dose of the drug. 

Men with breast cancer may be given letrozole, although another drug called tamoxifen is more commonly used.

2. How does letrozole work?

Letrozole works by reducing the amount of oestrogen made in the body. 

Some breast cancers are stimulated to grow by the hormone oestrogen. These are known as oestrogen receptor positive or ER+ breast cancers. 

Letrozole belongs to a group of drugs called aromatase inhibitors.

3. Who it’s suitable for

Letrozole is suitable for women who have been through the menopause and whose breast cancer is oestrogen receptor positive.

Sometimes letrozole is given alongside a drug called goserelin (Zoladex) to women who haven’t yet been through the menopause. 

If your cancer is hormone receptor negative, then letrozole will not be of any benefit.

4. Side effects of letrozole 

Find out more about the side effects of letrozole

5. When letrozole is given

Letrozole is usually given after surgery to reduce the risk of breast cancer coming back or spreading.

If you’re having chemotherapy or radiotherapy, your specialist will tell you when it’s best to start letrozole. 

Occasionally, letrozole may be used as the first treatment for breast cancer, for example when surgery isn’t appropriate or needs to be delayed. It’s sometimes given before surgery to shrink a larger breast cancer.

Letrozole can also be used to treat breast cancer that has come back (recurrence). It can also be given to treat breast cancer that has spread to another part of the body (secondary breast cancer), when it’s often given alongside another drug. 

6. How long will I have to take it? 

This will depend on your individual circumstances, but letrozole is usually taken for five to ten years.

Some people start taking letrozole after a few years of taking the hormone therapy drug tamoxifen

If you’re taking letrozole to treat breast cancer that has come back or spread to another part of the body, you’ll usually take it for as long as it’s keeping the cancer under control.

Stopping letrozole

Your treatment team will tell you when to stop taking letrozole. You won’t need to stop taking it gradually. 

Some people worry about stopping their treatment, but there’s evidence that letrozole continues to reduce the risk of breast cancer coming back for many years after you stop taking it.

However, not taking the drug for the recommended time may increase the risk of your breast cancer coming back. If you’re thinking about stopping taking letrozole for any reason, talk to your specialist first. Sometimes it may be possible to change to another hormone drug.

Hormone therapy is a very common treatment for secondary breast cancer and many people take it for a long time. If letrozole stops working, your specialist may prescribe another hormone drug. 

If you have any worries or questions about taking or stopping letrozole, you can call us free on 0808 800 6000 to talk through your concerns.

7. How it’s taken

Letrozole is taken as a tablet once a day, with or without food. It’s best to take it at the same time every day.

If you miss a dose, you don’t need to take an extra dose the next day. The level of drug in your body will remain high enough from the day before.

8. Taking letrozole with other drugs 

If you’re taking any other prescribed or over-the-counter medicines, check with your treatment team or pharmacist if you can take these with letrozole.

Do not take other drugs containing oestrogen, such as hormone replacement therapy (HRT), while you’re taking letrozole as this may interfere with its effectiveness. 

Talk to your specialist, pharmacist or GP about any complementary therapies, herbal remedies or supplements you want to use before you start using them.

Last reviewed: February 2019
Next planned review begins 2021

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