IMRT (Intensity Modulated Radiotherapy) at Guildford Hospital

Intensity-modulated radiotherapy (IMRT) is a precise form of radiotherapy that shapes and varies the strength of the radiation beam as it's aimed at your tumour, so different parts get exactly the dose they need. This lets your team give a higher dose to the cancer while sparing more of the healthy tissue around it, compared with older radiotherapy techniques.

What conditions does it treat?

IMRT is used across a wide range of cancers, and your radiotherapy team will let you know if it's a suitable option for you.

• Head and neck cancers
• Prostate cancer
• Breast cancer
• Lung cancer
• Central nervous system tumours
• Gynaecological and liver (hepatic) tumours
• Lymphomas and sarcomas.

It can be used on its own, or alongside surgery, to target any cancer cells left behind after an operation.

What are the benefits of IMRT?

• A higher, more effective dose can be delivered to the tumour while sparing more of the surrounding healthy tissue, with fewer side effects than older radiotherapy techniques.
• Treatment can be planned around the exact shape, size and position of your tumour.
• It's changed the standard of care for some cancers: some head and neck cancers that once needed surgery, and anal cancer, which used to mean a permanent colostomy bag, can now be treated with radiotherapy alone in many cases.
• For lung cancer, it's meant more people can have radiotherapy aimed at curing the cancer rather than just controlling symptoms.It can allow larger tumours, and tumours close to sensitive organs, to be treated safely when this wasn't previously possible.

Are there different types of approaches?

IMRT has developed since it was first introduced.

• Originally, it was given using several beams fired from fixed positions around you, each one touching healthy tissue only briefly as the machine worked through the different angles.
• Many modern machines now deliver IMRT in a single, smooth arc around you, which shortens the appointment.
• Some treatment plans use hypofractionated radiotherapy, giving larger doses over a shorter overall course rather than smaller daily doses over many weeks.

What happens before treatment?

Before your course of IMRT begins, your team will carry out a physical examination and review your medical history. You'll then have a planning appointment, called a simulation, so treatment can be mapped out precisely.

• A CT scan, taken in the exact position you'll lie in for treatment.
• Sometimes an additional PET or MRI scan, to help define the tumour more clearly.
• A small mark or tattoo placed on your skin, to help line up the equipment at each session.
• For some patients, a mould or mask made to hold you in the same position each time.
• Depending on where your cancer is, you may be asked to follow a bowel or bladder routine, or to fast, before your scan and early sessions.

If you're having IMRT for prostate cancer, for example, this can also mean stopping blood-thinning medicines a few days beforehand, having an enema, and adjusting your diet to reduce bloating. Treatment usually starts one to two weeks after your planning scan.

What happens during the procedure?

1. You'll be booked in for sessions 5 days a week, for a total of around 5 to 8 weeks, depending on your cancer.
2. At each visit, the radiotherapy team position you on the treatment table using your skin marks or tattoo, and your mould or mask if one was made, so you match your planning scan exactly.
3. The team then leaves the room. You'll be watched constantly on camera and can talk to them throughout.
4. The machine moves around you, reshaping and adjusting the strength of the beam as it goes, either in a smooth arc or from several fixed angles.
5. You won't feel the radiation itself, though you'll hear the machine, and may notice a smell or a warning light. You'll need to lie completely still, and the team can stop the machine at any point if you're uncomfortable.
6. After a few minutes, the machine switches off and the team returns to help you up. Each appointment usually takes between 15 and 90 minutes in total, most of it spent on positioning rather than treatment itself.

What does recovery look like?

IMRT is given on an outpatient basis, so you'll go home after each session rather than staying in hospital.

• Rest when you need to, including short naps in the day if you're tired.
• Keep the treated skin clean and moisturised.
• Drink plenty of fluids.
• Cut back on alcohol, caffeine and spicy food, as these can make some side effects worse.

Your oncologist will see you regularly once your course has finished, to check how well treatment has worked and to look out for any complications. Because some side effects can take months or years to appear, this follow-up continues well beyond the end of your sessions.

What are the risks and complications?

Side effects depend on which part of your body is being treated. Early side effects usually appear during or shortly after treatment and settle within a few weeks.

• Tiredness (fatigue)
• Skin changes in the treated area, such as sensitivity, redness, irritation, dryness, itching, peeling or blistering
• Hair loss in the treatment area
• Mouth problems or difficulty swallowing
• Eating and digestion problems, including nausea, vomiting or diarrhoea
• Urinary and bladder changes, such as needing to go more often, or, for pelvic treatment, bowel changes like rectal bleeding or erectile dysfunction.

Late side effects are less common and, although often permanent, tend only to appear months or years after treatment.

• Changes affecting the brain, spinal cord, lungs, kidneys, or colon and rectum, depending on the treatment area
• Infertility
• Joint changes
• Lymphoedema (fluid retention and swelling)
• A slightly increased risk of a second cancer developing later on.