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Medical x-rays and cancer

Doctor looking at a chest X-rayMedical x-rays are a very important tool for diagnosing different illnesses, including cancer. The health risks from x-ray radiation are generally very low and usually outweighed by the benefits of getting the right diagnosis and appropriate treatment.

X-rays are a form of ionising radiation, a high-energy type of radiation that can damage DNA in our cells. This damage has the potential to lead to cancer, but because medical x-rays only use small amounts of radiation, the risks involved are generally low.

Common types of medical x-rays

There are different types of medical imaging tests using x-rays that you may come across:

  • radiography to look at broken bones or your teeth and chest
  • mammography to screen for breast cancers
  • computed tomography (CT) to detect different diseases, including some cancers
  • fluoroscopy, such as a barium x-rays to look at your digestive system


How much radiation?

These tests all involve different amounts of radiation. The table below, taken from the Health Protection Agency, tells you how each test affects the odds of developing cancer over a person’s lifetime.

Type of medical imaging test Lifetime additional cancer risk for each examination
X-rays of chest, teeth, arms & legs, hands & feet Less than 1 in 1,000,000
X-rays of head, neck, skull 1 in 1,000,000 to 1 in 100,000


X-rays of hip, spine, abdomen and pelvis

CT scan of the head

1 in 100,000 to 1 in 10,000

Fluoroscopy: barium enema and barium swallow

CT scans of the chest and abdomen

1 in 10,000 to 1 in 1,000


The Health Protection Agency has produced an excellent patient information leaflet and detailed FAQs about medical radiation. These give you more information about radiation in medical imaging.

Avoiding unnecessary x-rays

Clinically relevant x-rays are very important.

But if you are concerned about having a large number of x-rays, you should talk to your doctor about it. You should also tell your doctor of previous x-rays you may have had. They may be useful for diagnosing, managing or treating your current condition. And they may mean that you do not need to have more x-ray tests.

Be careful about commercially available medical scans.

Some commercial companies offer ‘full body’ CT scans to the public. These generally cover your chest, abdomen and pelvis. These scans are likely to do more harm than good for people without medical symptoms.

They may diagnose conditions which would never have caused you any problems and may lead to unnecessary treatment. A ‘full body’ CT scan also uses 500 times the amount of radiation of a single chest x-ray. This may be necessary for people with a genuine medical need. But for healthy individuals without medical symptoms, the risks generally outweigh the benefits.

What affects our risk?

We all have a 1 in 3 risk of developing cancer in our lifetime. Medical x-rays only contribute a small amount overall to this risk. But unnecessary x-rays should be avoided.

Young patients are more at risk. Children and young adults up to the age of 16 have about double the risk of radiation induced cancers than older patients (ages 17 - 69). This is because children have a longer expected lifetime ahead of them during which radiation cancers could develop. Children are also still growing and have more rapidly dividing cells that can be affected by radiation.

The risk for patients over 70 years is very small. There is generally simply not enough time for radiation induced cancers to arise.

Unborn babies are also at higher risk. So women should tell their doctor if they are pregnant. The doctor will then assess whether an x-ray is necessary or whether a lead shield could be used to protect the baby.

Women also have a slightly higher lifetime risk of developing radiation-induced cancers than men for the same x-ray exposure at the same age.

A sense of perspective

We are exposed to radiation from natural sources every day. Radon gas from the earth’s crust contributes the largest amount of natural radiation to most people living in the UK. Cosmic rays from the sun, stars and outer space, natural radiation from the food we eat, the water we drink and the ground we walk on, also contribute to our natural exposure every day.

Medical x-rays just add a small amount of extra radiation on top of this and can bring great benefits to patients, by leading to accurate diagnosis and effective treatment.

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Question about cancer? Contact our information nurse team
Updated: 31 August 2010