What is Letrozole?

Letrozole is a medication used to treat breast cancer. It is often called by its brand name, Femara. Letrozole belongs to a group of drugs called aromatase inhibitors. These drugs work by lowering the amount of the hormone estrogen in the body. Some breast cancers use estrogen to help them grow. These cancers are called “estrogen receptor positive” or “ER positive” breast cancers. By blocking estrogen, letrozole can slow or stop the growth of these ER positive breast cancers.

Who is Letrozole Used for?

  • Postmenopausal women with ER positive breast cancer
  • Premenopausal women with ER positive breast cancer who are also receiving ovarian suppression therapy
  • Occasionally, men with ER positive breast cancer

Letrozole is not helpful for people with estrogen receptor negative (ER negative) breast cancers.

When is Letrozole Given?

Doctors may prescribe letrozole at different times during breast cancer treatment:

  • After surgery, to help prevent cancer from coming back or spreading to other parts of the body
  • Before surgery, to try to shrink larger tumors so less extensive surgery is needed
  • During chemotherapy or radiation, on a schedule recommended by your cancer doctor
  • As the first treatment for breast cancer when surgery needs to be delayed or isn’t an option
  • To treat recurrent or metastatic cancer – letrozole may be used when cancer comes back after initial treatment or spreads to sites like the bones, brain, liver etc.

How Long is Letrozole Taken?

If using letrozole to prevent recurrence after early stage breast cancer, the typical duration is 5-10 years. For recurrent or metastatic cancer, most patients take letrozole continuously for as long as it keeps working.

How Does Letrozole Work?

Letrozole is taken as a tablet by mouth, once per day. It can be taken with or without food. Try to take it at the same time each day. If you miss a dose, you do not need to take an extra tablet the next day. Letrozole tablets contain small amounts of lactose. If you are lactose intolerant, tell your doctor – they may recommend a different brand or type of tablet for you.

What are the Side Effects?

Like most medications, letrozole can cause some side effects. However, not everyone experiences side effects. Common side effects can include:

  • Hot flashes – sudden feelings of warmth in the face, neck and chest
  • Night sweats
  • Vaginal dryness and painful intercourse
  • Joint pain or stiffness
  • Fatigue

Rarer but more serious side effects may include thinning bones (osteoporosis), high cholesterol, heart problems or vision changes. If side effects bother you, talk to your doctor. There may be ways to manage them. There are also other hormone therapy options if needed.

Important Reminders

  • Avoid pregnancy while on letrozole – use non-hormonal birth control like condoms or an IUD.
  • Do not take letrozole if pregnant – contact your doctor right away if you become pregnant.
  • Check herbals or supplements with your medical team before starting them.
  • Tell your doctor about any other medicines you take to check for interactions with letrozole.

Let your doctor know if you have any other medical conditions before starting this medication. Stopping letrozole abruptly is not recommended – talk to your doctor first about any concerns with treatment.

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