Aromatase is an enzyme that works to help produce the hormone estrogen. Some cancers use estrogen to grow. By inhibiting aromatase, these estrogen-driven cancer cells may stop growing.
In women who have gone through menopause, estrogen is mainly produced by converting androgens (sex hormones produced by the adrenal glands) into estrogens. While estrogen may not actually cause breast cancer, it is a necessary hormone for the cancer cells to grow in estrogen receptor-positive breast cancers. With estrogen blocked, the cancer cells that feed off estrogen may not be able to survive.
Letrozole comes in tablet form and is taken by mouth once daily. Letrozole can be taken with or without food. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not take two doses at the same time. Do not stop taking letrozole without talking to your healthcare team.
It is important to make sure you are taking the correct amount of medication every time. Before every dose, check that what you are taking matches what you have been prescribed.
This medication can cause fatigue, dizziness, and somnolence. You should not drive or operate heavy machinery until you know how this medication will affect you.
The blood levels of this medication can be affected by certain foods and medications, so they should be avoided. Be sure to tell your healthcare provider about all medications and supplements you take. You should not take this medication if you are currently taking tamoxifen or other medications that include estrogen, including hormone replacement therapy, birth control pills, estrogen creams, vaginal ring, and vaginal suppositories.
Store this medication at room temperature in the original container. If you prefer to use a pillbox, discuss this with your oncology pharmacist. Ask your oncology team where to return any unused medication for disposal. Do not flush down the toilet or throw it in the trash. Keep containers out of reach of children and pets.
If a caregiver prepares your dose for you, they should consider wearing gloves or pour the pills directly from their container into the cap, a small cup, or directly into your hand. They should avoid touching the pills. They should always wash their hands before and after giving you the medication. Pregnant or nursing women should not prepare the dose for you.
Letrozole is available through retail or mail-order pharmacy. Your oncology team will work with your prescription drug plan to identify an in-network, retail, or mail-order pharmacy for medication distribution.
This medication may be covered under your prescription drug plan. Patient assistance may be available to qualifying individuals without prescription drug coverage. Co-pay cards, which reduce the patient’s co-pay responsibility for eligible commercially (non-government sponsored) insured patients, may also be offered by the manufacturer. Co-pay assistance from private third-party foundations may be available. Your care team can help you access these resources if they are available.
There are a number of things you can do to manage the side effects of letrozole. Talk to your care team about these recommendations. They can help you decide what will work best for you. These are some of the most common or important side effects:
There are a few things you can do to help with hot flashes. Several medications have been shown to help with symptoms, including clonidine (a blood pressure medication), low doses of certain antidepressants (such as venlafaxine and fluoxetine), and gabapentin. Talk to your healthcare team about these prescription products to determine if they are right for you.
Non-medical recommendations include:
Fatigue is very common during cancer treatment and is an overwhelming feeling of exhaustion that is not usually relieved by rest. While on cancer treatment, and for a period after, you may need to adjust your schedule to manage fatigue. Plan times to rest during the day and conserve energy for more important activities. Exercise can help combat fatigue; a simple daily walk with a friend can help. Talk to your healthcare team for helpful tips on dealing with this side effect.
Aromatase inhibitor medications can cause joint or muscle aches and pains, which can interfere with quality of life. Be sure to talk to your oncology care team if you develop this side effect. This pain is caused mainly by swelling in the joints, which is best treated by a non-steroidal anti-inflammatory (NSAID), such as ibuprofen (Advil/Motrin), naproxen (Aleve), and celecoxib (Celebrex). Be sure to discuss which pain relievers you can safely take with your oncology team, as these are not without their own side effects. Studies have shown that acupuncture and gentle stretching and exercise may also help reduce this pain.
You may be advised to take calcium and vitamin D supplements to help prevent bone loss. Weight-bearing exercise and a healthy diet rich in calcium and vitamin D can also help protect your bone health. Your doctor will check your bone health before starting therapy. This is done with a bone density scan (DEXA scan). Women with no weakening of bones prior to aromatase inhibitor therapy will have a follow-up scan around one year after starting therapy, and then every one to two years. If the scan shows that you already have some bone weakening, your doctor may order a type of medication called a bisphosphonate. These therapies have been shown to protect the bones from bone loss in women taking aromatase inhibitors. If the bone density remains stable, scans can then be done every two years.
Vaginal dryness and related painful intercourse are common side effects of cancer therapy in women. Vaginal lubricants and moisturizers (longer-lasting forms of moisturizers) can help with these concerns. Talk to your healthcare team for more suggestions for managing this side effect.
Letrozole can cause an increase in your cholesterol levels. Your healthcare team will monitor your cholesterol levels throughout your treatment.
Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant while on this medication. Effective birth control is necessary during treatment and for three weeks after treatment if your menopause status has not been confirmed. You should not breastfeed while receiving this medication and for three weeks after your last dose.