Megestrol is a hormonal therapy drug used to treat breast and womb cancer that has spread to other parts of the body (secondary cancer). It may also be used to treat breast and womb cancer that has come back after treatment (recurrent).
Megestrol can also be used to improve your appetite.
It is best to read this information with our general information about hormonal therapies and the type of cancer you have.
Your doctor will talk to you about this treatment and its possible side effects before you agree (consent) to have treatment.
How megestrol works
Hormones are chemicals that our bodies make. Hormones act as messengers and help control how cells and organs work. Hormonal therapies are drugs that change the way hormones are made or how they work in the body.
Many cancers need hormones to grow. Megestrol is similar to the female sex hormone progesterone. It works by changing the hormone balance in the body, which may stop the cancer growing. It can also act directly on cancer cells so that they cannot grow.
We explain the most common side effects of this treatment here. We also include some less common side effects. You may get some of the side effects we mention, but you are unlikely to get all of them.
If you are also having treatment with other cancer drugs, you may have some side effects that we haven’t listed here. Always tell your doctor, nurse or pharmacist about any side effects you have.
Your doctor can give you drugs to help control some side effects. It is important to take them exactly as your nurse or pharmacist explains. This means they will be more likely to work for you. Your nurse will give you advice about managing your side effects. After your treatment is over, most side effects start to improve.
Serious and life-threatening side effects
Some cancer treatments can cause severe side effects. Rarely, these may be life-threatening. Your cancer doctor or nurse can explain the risk of these side effects to you.
Contact the hospital
Your nurse will give you telephone numbers for the hospital. If you feel unwell or need advice, you can call them at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.
We cannot list every side effect for this treatment. There are some rare side effects that are not listed. You can visit the electronic Medicines Compendium (eMC) for more detailed information.
Increased appetite and weight gain
This treatment can make you feel more hungry than usual. If you are eating more, you may gain weight. This effect on your appetite will go away when you stop taking the drug. If you are worried about gaining weight, talk to your doctor or nurse.
Because of this side effect, this treatment is sometimes used to treat people who have lost interest in food and are losing weight.
This treatment can cause constipation. Here are some tips that may help:
- Drink at least 2 litres (3½ pints) of fluids each day.
- Eat high-fibre foods, such as fruit, vegetables and wholemeal bread.
- Do regular gentle exercise, like going for short walks.
If you have constipation, contact the hospital for advice. Your doctor can give you drugs called laxatives to help.
Hot flushes and sweats
These are common. During a flush, your neck and face may feel warm and look red. Flushes can last for a few seconds or for up to 10 minutes. You may have sweats then feel cold and clammy. Some people feel anxious or irritable during a hot flush.
There are things you can do to try to reduce flushes:
- Wear clothes made from natural fabrics, such as cotton.
- Dress in layers of clothes that you can remove as needed.
- Use cotton sheets and have layers of bedding.
- Keep the room temperature cool or use a fan.
- Have cold drinks rather than hot ones. Try to avoid drinks with caffeine in them.
You may have fewer hot flushes and sweats as your body adjusts to hormonal treatment. Or your doctor can prescribe drugs to help. Some people continue to have flushes and sweats, but they usually stop a few months after treatment finishes.
Women coping with hot flushes can read more in our information about managing menopausal symptoms.
High blood pressure
Raised blood sugar levels
This treatment can raise your blood sugar levels. If you have a raised blood sugar level, you may:
- feel thirsty
- need to pee (pass urine) more often
- feel tired.
Tell your doctor or nurse if you have these symptoms.
If you have diabetes, your blood sugar levels may be higher than usual. Your doctor will talk to you about how to manage this. You may need to adjust your insulin or tablet dose.
If you do not have diabetes, there is a small risk of developing diabetes when taking megestrol. Your doctor or specialist nurse can discuss this with you further.
Blood clot risk
Cancer and some cancer treatments can increase the risk of a blood clot. Symptoms of a blood clot include:
- pain, redness or swelling in a leg or arm
- chest pain.
If you have any of these symptoms, contact a doctor straight away.
A blood clot is serious, but can be treated with drugs that thin the blood. Your doctor or nurse can give you more information.
Feeling tired is a common side effect. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can give you more energy. If you feel sleepy, do not drive or operate machinery.
Some people feel sick, especially during the first few weeks of taking this treatment. Tell your doctor if you feel sick. They can prescribe anti-sickness drugs to help.
Some people have mood changes and feel low or depressed when having this treatment. Let your doctor or nurse know if you notice any changes.
Memory and concentration
You may notice changes in your memory or ability to concentrate. To help you remember things, try using:
- a notebook
- notes on your phone
- a calendar.
This treatment may affect your skin. Your doctor or nurse can tell you what to expect. If your skin feels dry, try using an unperfumed moisturising cream every day. The treatment may cause a rash, which may be itchy.
Always tell your doctor or nurse about any skin changes. They can give you advice and may give you creams or medicines to help. Any changes to your skin are usually temporary and improve when treatment finishes.
Change in periods
Most men lose their sex drive and have erection difficulties during hormonal therapy. Things often return to normal after you stop taking the drug, but some men continue to have difficulties after treatment is over.
Your doctor can prescribe treatments to help with erection difficulties. But these treatments will not increase sex drive.
Swollen hands, feet and ankles
If you are having this treatment for cancer that has spread to the bones, you may get pain in the bones when you start taking it. Doctors call this tumour flare. Your doctor can give you treatment to help with this.
Tumour flare can also cause high calcium levels in the blood (hypercalcaemia). Your doctor will do regular blood tests to check your calcium levels. If your calcium levels are high, you may:
- feel sick or vomit
- be very thirsty
- be constipated
- feel confused.
If you have any of these symptoms, let your doctor know straight away so they can treat it.
If you have diarrhoea, contact the hospital for advice. Try to drink at least 2 litres (3½ pints) of fluids every day. It can help to avoid alcohol, caffeine, milk products, high-fat foods and high-fibre foods.
Some medicines can affect the hormonal treatment or be harmful when you are having it. This includes medicines you can buy in a shop or chemist. Tell your cancer doctor about any drugs you are taking, including vitamins, herbal drugs and complementary therapies.
Your doctor will advise you not to get pregnant or make someone pregnant while having this treatment. The drugs may harm a developing baby. It is important to use contraception during your treatment and for a while after treatment finishes. Your doctor, nurse or pharmacist can tell you more about this.
Women are advised not to breastfeed while having this treatment. This is because the drugs could be passed to the baby through breast milk.
Medical and dental treatment
If you need medical treatment for any reason other than cancer, always tell the doctors and nurses that you are having cancer treatment. Give them the contact details for your cancer doctor so they can ask for advice.
If you think you need dental treatment, talk to your cancer doctor or nurse. Always tell your dentist you are having cancer treatment.