The possible benefits of treatment vary, for some people hormonal therapy may reduce the risk of cancer coming back, for others it may control the cancer and its symptoms. Your clinical team will be happy to answer any questions you have about your treatment. Letrozole may be prescribed on its own or in combination with other anti-cancer therapies.
Your treatment
Letrozole tablets are taken once a day continuously until your clinical team tells you otherwise. Swallow the tablets whole with a glass of water. You can take it with or without food. Try to take it at the same time each day, morning or evening.
If you forget to take the tablets, take the missed dose as soon as possible within the same day. If it is nearly time for the next dose (within 2 to 3 hours), the missed dose should be skipped. Do not double up. Take your next dose when it is due.
If you vomit after taking your tablets, do not take an extra dose. Take your next dose at the normal time.
Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies are drugs that interfere with the way hormones are made or how they work in the body.
Many breast cancers rely on the hormone oestrogen to grow. This type of breast cancer is called oestrogen receptor-positive (ER positive) breast cancer.
In women, after the menopause, oestrogen is no longer made in the ovaries. Instead, it is made in the fatty tissues of the body. This happens when an enzyme (a type of protein) called aromatase changes other hormones into oestrogen. Letrozole is a type of drug called an aromatase inhibitor. It blocks (inhibits) the activity of aromatase and reduces the amount of oestrogen in the body. This means that the cancer may grow more slowly or stop it growing altogether.
Letrozole may also be used in men, patients who were assigned male at birth, or in patients who have not gone through the menopause. In this case, letrozole will be combined with goserelin or leuprorelin injections.
If you feel unwell, you have symptoms of an infection or your temperature is 37.5ºC or above, or below 36ºC contact The Christie Hotline straight away.
Possible side effects
Hormonal therapy can cause different side effects. Some are more likely to occur than others. Everyone is different and not everyone gets all the side effects.
Most side effects are usually temporary, but in some rare cases they can be life-threatening. It is important to tell your clinical team about any side effects so they can be monitored, and where possible, treated.
Common side effects (more than 1 in 10)
Hot flushes
Hot flushes and sweats may occur but do lessen after the first few months. Cutting down on nicotine, alcohol and hot drinks containing caffeine, such as tea and coffee can help. Dress in layers, so you can remove clothes as needed. Natural fabrics, such as cotton may feel more comfortable.
If hot flushes are a problem, tell your doctor. Low doses of certain antidepressant drugs can help reduce flushes.
Bone thinning
Taking letrozole for a few years increases your risk of bone thinning, called osteoporosis. This can increase your risk of a broken bone (fracture). You will usually have a bone density scan to check your bone health before and during treatment.
If you are at risk of osteoporosis, your doctor may prescribe drugs called bisphosphonates to protect your bones. They will also usually advise you to take vitamin D supplements (20 micrograms or 800 international units minimum daily dose). Calcium supplements are rarely necessary as most patients have an adequate dietary intake of calcium. Regular walking, eating a healthy diet, not smoking and sticking to sensible drinking guidelines will also help strengthen your bones.
Fatigue (tiredness)
You may feel tired, sleepy or feel like you have no energy when you start taking letrozole. Try to pace yourself until this improves. It's important to get the right balance of having enough rest and being physically active. Regular short walks will help you to feel less tired. If you feel sleepy, don't drive or operate machinery.
Joint and muscle pain
You may have pain and stiffness in your joints, and sometimes in your muscles while taking letrozole. Let your clinical team know if this happens. They can prescribe painkillers and give you advice. Being physically active and maintaining a healthy weight can help reduce joint pain and keep them flexible.
Sickness and diarrhoea
Any sickness is usually mild, but let your clinical team know if this happens. Letrozole may also cause indigestion or tummy pain. Let them know if you have any of these symptoms. They can prescribe drugs to help.
If diarrhoea becomes a problem during or after your treatment, anti-diarrhoeal tablets can be prescribed by your doctor. Ask the staff for a copy of the booklet 'Eating: help yourself' which has some useful ideas about diet when you are having treatment.
Constipation
You may become constipated. Try to drink plenty of fluids and eat foods which are high in fibre. Tell your clinical team who may prescribe a suitable laxative. Please contact The Christie Hotline if your constipation lasts more than 3 days or you experience abdominal discomfort.
Increase in appetite/weight gain
Some patients find their appetite increases. Eating healthily and being physically active will help if you have concerns about your weight. Alternatively if you don't have much appetite, try eating small, frequent meals or snacks. If problems with eating don't get better talk to your clinical team.
Skin rash and dry skin
You may get a mild skin rash. Tell your doctor or nurse if this happens. It is very important to contact your clinical team straightaway if you get a severe skin rash.
Headache and dizziness
If you have headaches, let your clinical team know. They can usually be controlled with painkillers you can buy yourself. Letrozole may cause dizziness. Let your clinical team know if this is a problem.
Vaginal bleeding and dryness
For some patients, letrozole causes vaginal bleeding. If this happens, it is most likely to be in the first few weeks of treatment, or when you change from another hormonal therapy to letrozole. If the bleeding continues for more than a few days, tell your clinical team.
For some patients, letrozole causes vaginal dryness. Non-hormonal creams and gels or lubricants can help reduce dryness and discomfort during sex. You can buy these at a chemist or your GP can prescribe them.
Your sex drive may also be lower while taking letrozole. Talk to your clinical team for advice. Although breast cancer is less common in men, this treatment can affect male hormones. This may lead to changes in sex drive and sexual function including erectile dysfunction. Talk to your GP for advice if these become an issue.
Fast heartbeat/raised blood pressure
Some patients may find that their heart is racing (palpitations) or have chest pain while taking letrozole. Always call 999 if you have any chest pain or difficulty breathing.
Tell you clinical team if you have ever had any problems with your blood pressure, your clinical team will check your blood pressure in clinic.
Raised lipid (fat) levels
Your clinical team may check your lipid levels (such as cholesterol) with a blood test.
Uncommon side effects (less than 1 in 10)
Insomnia (sleep issues)
These tablets may cause sleep disturbance. If this becomes a problem tell your clinical team.
Mood changes/memory issues/difficulty concentrating
Some people find that they have a low mood while taking letrozole. Some people may notice changes in their memory, have problems concentrating, feel anxious or have difficulty sleeping. Talk to your GP if you have these issues so they can give you support and advice.
Urinary infection
Let your clinical know if you have pain or discomfort when you pass urine, if you need to pass urine more often, or if your urine is cloudy or smelly. Drink lots of fluids if you think you may have an infection.
Eye irritation/blurred vision
This treatment can cause cataracts (clouding of the lens of the eye) or other eye problems including sore eyes or blurred vision. Always tell your clinical team if you notice any change in your vision.
Sore mouth and strange taste
While taking this treatment, your mouth may become sore. Ask your clinical team for advice. Occasionally during treatment you may experience a strange taste, sometimes described as metallic or bitter. A strongly flavoured sweet or mint will help to disguise this.
Chest tightness or pain
If you notice changes to your heartbeat, such as it speeding up, let your clinical team know. If you have pain or tightness in your chest, or feel breathless at any time during or after treatment, call 999 immediately.
Hair thinning
While you are taking this treatment your hair may become thinner, drier and more brittle. This is usually mild. Your hair will return back to normal after treatment finishes.
Liver changes
Letrozole can sometimes cause changes in the way your liver works. Your clinical team will arrange for you to have regular blood tests to check your liver is working properly. You are very unlikely to notice any problems.
Fluid build-up
You may put on weight, or your ankles and legs may swell because of fluid building up. Tell your clinical team if this happens. If your ankles and legs swell, it can help to put your legs up on a foot stool or cushion.
Late side-effects
Some side-effects may become evident only after a number of years. In reaching any decision with you about treatment, the potential benefit you receive from treatment will be weighed against the risks of serious long term side effects to the heart, lungs, kidneys and bone marrow. With some drugs, there is also a small but definite risk of developing another cancer.
If any of these problems specifically applies to you, the doctor will discuss these with you and note this on your consent form.
Sex, contraception and fertility
Letrozole is usually used when you have been through the menopause. However, if you have recently been though the menopause, had a chemotherapy-induced menopause or are having treatment to stop your ovaries working, there is still a small chance that you could become pregnant.
It is important not to get pregnant while having this treatment as this drug may harm a developing baby. If you are sexually active, you must use effective contraception while taking letrozole, such as a barrier form of contraception.
Flu vaccinations
We advise that all patients receive a flu vaccination when this is offered. However, if you are thinking of having any other vaccines, check with your Christie doctor first, because some vaccines should be avoided.
COVID-19 vaccinations
We advise that all patients receive a COVID-19 vaccination when this is offered.
Other medicines
Some medicines and herbal remedies may interact with letrozole. Please consult your doctor or pharmacist if you are starting any new medications.
Contacts
If you have any general questions or concerns about your treatment, please contact your consultant's secretary or your breast cancer nurse.
For advice, ring The Christie Hotline on 0161 446 3658 (24 hours a day, 7 days a week).