Side effects often build up slowly during treatment and it could be a few days or weeks before you notice anything. Often the side effects are worse at the end of treatment, or even a week or two afterwards, because it takes time for the healthy cells to recover from radiation.

Radiation therapy can also cause side effects that last for months or years after treatment. These long-term effects are usually mild, they may come and go, and they may not have any major impact on your daily life. Sometimes they may be more serious.

Late side effects may go away or improve on their own, but some may be permanent and need to be treated or managed.

Very rarely, years after successful treatment, patients can develop a new unrelated cancer in or near the area treated. The risk of this late effect is very low, but other factors, such as continuing to smoke or very rare genetic conditions, can increase this risk.

Radiation therapy to the chest, particularly when combined with chemotherapy, may lead to an increased risk of heart problems. Newer techniques have reduced the risk, however, talk to your doctor about your heart health.

If you develop heart problems later in life, make sure you let your doctors know you had radiation therapy.

• Clean your skin with warm water and a mild unscented soap. Gently pat skin dry with a soft towel.
• Ask your doctor or nurse what type of water-based moisturiser to use. Avoid perfumed or scented products.
• Start moisturising from the first day of treatment. Apply moisturiser at least two hours before or after each session.
• Protect your skin outdoors. The sun can irritate skin changes and delay healing.
• Let temporary skin markings wear off by themselves. Don’t scrub your skin to remove them.
• Avoid using razors, hair dryers, hot water bottles, heat packs, wheat bags or icepacks on the area that has been treated.
• Wear loose, soft cotton clothing. Avoid tight-fitting items in the treatment area.
• Check with your doctor about swimming. Chlorine may worsen skin reactions for some people.

Appetite loss

• Don’t wait to feel hungry. Eat small meals every 2–3 hours during the day. Setting an alarm to remind you to eat may be helpful.
• Try to eat extra on days when you have an appetite.
• If you don’t feel like eating solid foods, try nourishing fluids, such as smoothies made with milk or milk powder. Add yoghurt, fruit, and nut butters for extra kilojoules and protein.
• Do not use nutritional supplements or medicines to improve your appetite without your doctor’s advice. They could affect treatment.
• Cooking smells may put you off eating. It might help if someone else prepares your food, or you could reheat precooked meals.
• Try to do some light physical activity, such as walking. This may improve your appetite.
• Let your treatment team know if you are having trouble eating or if your weight has changed.

Nausea

• Try food and drinks with ginger or peppermint to help reduce nausea.
• Sip on water and other fluids throughout the day to prevent dehydration.
• Have a bland snack (e.g. dry biscuits, porridge, crackers or toast).
• Ask your doctor if you can try anti-nausea medicine. It’s important to take anti-nausea medicine as directed to help prevent nausea – don’t wait until you feel sick. Let the doctor know if the medicine doesn’t help as they can offer you a different one to try.
• Contact your treatment team if the nausea doesn’t ease after a few days, or if you have been vomiting for more than 24 hours.
• See Nutrition for People Living with Cancer.

For more support, listen to The Thing About Cancer podcast episode on appetite loss and nausea  or call 13 11 20 to speak to our cancer nurses.

This is when you have many loose, watery bowel motions. Diarrhoea can also cause abdominal cramping, wind and pain. After radiation therapy, you will need to go to the toilet more urgently and more often.

Having diarrhoea can be tiring, so rest as much as possible and ask others for help. Diarrhoea can take some weeks to settle down after treatment has finished.

Radiation therapy to the pelvic area can damage the lining of the rectum, causing inflammation and swelling known as radiation proctitis.

Symptoms may include blood and mucus in bowel motions, discomfort opening the bowels or the need to empty the bowels often, perhaps with little result.

Ask your radiation oncologist about your risk of developing radiation proctitis. It is usually short term but may be ongoing in a small number of people. 

Rarely, after radiation therapy to the pelvis, especially if you have had previous abdominal surgery, you may develop a bowel blockage. This can be serious.

It is important to let you doctor and treatment team know if you have pain in the abdomen, vomiting and difficulty opening your bowels.

• Ask your doctor about suitable medicines for diarrhoea. Take as directed.
• Check with your treatment team before taking any over-the-counter or home remedies, as taking them with anti-diarrhoea medicines may cause side effects.
• Drink peppermint or chamomile tea to reduce abdominal or wind pain.
• Continue to eat or drink to avoid weight loss and give your body the nutrients it needs.
• Do some gentle exercise, such as walking, to encourage healthy bowel movements. Check with your doctor about the amount and type of exercise that is right for you.
• Try limiting caffeine from drinks such as tea, coffee, cols and other soft drinks as these can stimulate the bowel.
• Drink plenty of liquids when you first notice symptoms. This helps to avoid dehydration and replaces fluids lost through diarrhoea. Try apple juice, weak tea, clear broth, sports drinks and electrolyte-replacing fluids. It may also be worth trying a lactose-free milk.
• Choose plain foods that are low in insoluble fibre (e.g. bananas, mashed potato, apple sauce, white rice or pasta, white bread, steamed white fish or chicken). Talk to your dietitian about what else you can eat.
• Avoid high-fibre, fatty or fried foods, pulses, garlic and onion, and rich sauces and gravies, as these can make diarrhoea worse.
• Reduce sugar-free or diet soft drinks and sweets that contain sorbitol, mannitol and xylitol as these can make diarrhoea worse.
• Contact your treatment team immediately if there is blood in your bowel motions or if you have more than 5–6 bowel movements in 24 hours.

You may notice a lack of interest in sex or a loss of desire (libido), or you may feel too tired or unwell to want to be intimate. You may feel less sexually attractive to your partner because of changes to your body. All of these feelings are quite common.

Although it is usually safe to have sexual intercourse, it may be uncomfortable, depending on where the radiation therapy is given. Talk to your doctor about ways to manage side effects that change your sex life.

For more support, listen to  The Thing About Cancer podcast episode on sex and cancer .

A woman’s eggs (ova) and a man’s sperm can be affected by very small amounts of radiation when having radiation therapy to any part of the body.

Depending on the type of radiation therapy you have, your doctor may talk to you about using a barrier method of contraception (such as a condom or female condom).

If pregnancy is possible, your doctor will advise you to avoid pregnancy by using contraception during radiation therapy and for at least six months after you have finished treatment. Talk to your doctor as soon as possible if pregnancy occurs.

The risk of infertility (difficulty getting pregnant or conceiving a child) will depend on the area treated, the dose of radiation therapy and the number of treatment sessions.

If you are treated with both radiation therapy and chemotherapy (chemoradiation), the risk of infertility is higher.

Radiation therapy to the pelvic area, abdomen and sexual organs can affect your fertility, which can be temporary or permanent.

Radiation therapy to the brain can damage the pituitary gland, which controls the hormones the body needs to produce eggs or sperm.

If infertility is a potential side effect, your radiation oncologist will discuss it with you before treatment starts.

Let them know if you think you may want to have children in the future. Ask what can be done to reduce the chance of problems and whether you should see a fertility specialist beforehand.

Sometimes, however, it is not possible to properly treat the cancer and maintain fertility. Many people feel a sense of loss when they learn they may no longer be able to have children.

If you have a partner, talk to them about your feelings. Talking to a counsellor may also help.