Understanding radiotherapy: what to expect, types and side effects

Radiotherapy is a cancer treatment that may be given alone or with surgery or chemotherapy. Not knowing what happens in the treatment room can cause worry. This article explains how radiotherapy works, the different types, what to expect and how side effects are managed. It uses information from the US National Cancer Institute and the NHS.

1. Introduction

Radiotherapy, also called radiation therapy, uses high levels of radiation to kill cancer cells and shrink tumours. At low levels, radiation is used in imaging such as X-rays ^[1]. The NHS explains that radiotherapy can have several aims: to try to get rid of the cancer, to make other treatments such as chemotherapy or surgery work better, to lower the chance of cancer returning after surgery, or to ease symptoms when the cancer cannot be removed ^[2].

2. How radiotherapy works

Radiation damages the genetic material, called DNA, inside cancer cells. Cells whose DNA cannot be repaired stop dividing or die, and the body clears them away. The effect is not immediate. It can take days or weeks of treatment for enough damage to build up, and cancer cells may keep dying for weeks or months after treatment ends ^[1].

Because radiation can also damage nearby healthy cells, side effects can occur ^{[1, 2]}.

3. Types of radiotherapy

The two main groups are external and internal radiotherapy ^{[1, 2]}.

• External beam radiotherapy. A machine aims radiation at the cancer from many directions without touching the body. It is a local treatment, so only the targeted area is treated ^[1].
• Implants (brachytherapy). Small pieces of radioactive material, such as seeds, ribbons or capsules, are placed in or near the tumour, usually for a limited time ^{[1, 2]}.
• Radioactive liquids. Radiation is swallowed or given through a vein and travels in the blood to reach cancer cells around the body. Examples include radioactive iodine for some thyroid cancers ^{[1, 2]}.

The NHS notes that external radiotherapy does not make you radioactive. The radiation from implants or radioactive liquids can stay in your body for a few days, so you may need to stay in hospital and avoid close contact with other people as a precaution ^{[2, 4]}. Permanent implants give off a very small amount of radiation that falls over time, but you may need to avoid close contact with children and pregnant women for a short time ^[4]. The National Cancer Institute adds that with external treatment you can safely be around others, including pregnant women, babies and young children ^[3].

4. Planning and what happens during treatment

Before treatment. Your care team recommends radiotherapy if they think it is the best option, but the final decision is yours. It can help to write down questions about the aim of treatment, side effects, how well it is likely to work and the alternatives ^[4]. The first meeting usually includes a physical examination, your medical history, possibly imaging, and a discussion of benefits and side effects ^[3].

Planning. You will probably have a CT scan to show the exact position and size of the cancer. Small marks may be placed on the skin so the same area is treated each time, and some are permanent ink marks. For treatment to the head or neck, a plastic mask or mould may be made to keep you still ^{[3, 4]}. Protect the marks and tell your therapist if they fade ^[3].

Sessions. Many people attend on weekdays, once a day, with weekends off. The number of weeks depends on the type of cancer, the aim of treatment and the schedule ^{[3, 4]}. If radiotherapy is only to ease symptoms, one session may be enough ^[4].

In the treatment room. You lie on a table while the machine directs the beams. Staff work the machine from another room but can watch you through a screen and talk to you through an intercom, and they can stop treatment at any time ^{[3, 4]}. You need to keep very still. The beam lasts only a few minutes, you breathe normally, treatment is painless and you can usually go home afterwards ^{[3, 4]}. Wear soft, loose clothing and avoid tight collars, jewellery and powder over the treated area ^[3].

5. Side effects and how they are managed

Side effects depend on the part of the body treated and on the type of radiotherapy. Many can be treated or prevented, and some appear months or years later, so ask your team what to expect ^[5]. The NHS lists these common effects and tips ^[5]:

• Sore skin. Redness, dryness and itching, and sometimes blistering or peeling, usually starting after one to two weeks. Washing gently, patting dry, moisturising, wearing loose natural fabrics and avoiding shaving in the area can help. Skin usually settles a few weeks after treatment.
• Tiredness. Often starts during treatment and can last weeks or months. Rest, light activity such as short walks and accepting help can help.
• Hair loss only in the treated area, with regrowth usually starting a few weeks after treatment, though texture or colour may change.
• Nausea, which is more likely when the stomach or brain is treated, and which often eases soon after treatment ends.
• Sore mouth, common with treatment of the head and neck, and diarrhoea, common with treatment of the tummy or pelvis.
• Effects on sex and fertility, especially if the lower tummy, pelvis or groin is treated. Ask your care team if there is a chance it could affect you, and about options such as storing eggs or sperm before treatment.
• Emotional effects such as stress and anxiety. Talking with your team or joining a support group can help.

The NHS also says radiotherapy slightly raises the long-term risk of another cancer, but this risk is small and generally outweighed by the benefits of treatment ^[5]. Women should avoid pregnancy during treatment, and the team should be told at once if pregnancy is possible ^[4].

6. Self-care during radiotherapy

Rest when you need to, try light exercise such as short walks if you are able to, and ask friends and family for help with everyday tasks ^[5]. If your appetite is low, try to eat healthily and keep your weight steady, and tell your team if you do not feel you are eating enough. They may suggest eating frequent small meals or send you to a dietitian ^[5]. Please also tell your team about every medicine, cream or remedy you use. If you are struggling and have doubts about continuing, speak to your care team, who can advise on the likely benefits of carrying on. The final decision is yours ^[4].

7. When to see a doctor

Tell your care team about any side effect, such as soreness or changes to your skin, or if you feel sick during or after treatment. Contact them if you are struggling to cope emotionally, if diarrhoea has not improved after a few weeks or you see blood in your stool, or if you suddenly feel very tired and out of breath, which can be a sign of anaemia, meaning a lack of red blood cells, that may need treatment ^[5].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

Radiotherapy uses radiation to kill cancer cells and shrink tumours, and it can be given from outside the body or from inside it. Sessions are short and painless, and most side effects fade after treatment ends. Knowing what to expect and speaking up early helps. Your cancer specialist decides if radiotherapy is right for you and plans it with you.