Mammography – the risks!

September 28th 2015

This week, Cathy Hill, Education and Training Lead at The Nightingale Centre & Genesis Prevention Centre offers an informative blog focusing on radiation and mammography.

How is a mammogram produced? It is a digital image produced when low dose radiation (but high energy) is converted in to an electrical signal which in turn produces an image. Not too unlike how your pocket camera produces holiday snaps, but without the radiation!

 

radiation3

Figure 1:

http://www.who.int/ionizing_radiation/about/what_is_ir/en/

What is radiation? According to the NHS choices web site, radiation refers to any sort of energy that can travel through space as a wave or particle.

Radiation is everywhere, in the ground; rocks and stones, and even in some foods, such as bananas. This is called background radiation and is unlikely to cause health problems as it is in such low levels.

Radiation can be split into two types;

  • Non-ionising, which is classed as low energy radiation
  • Ionising, which is classed as high energy radiation.

Whilst non–ionising radiation is unlikely to be harmful, there are still certain types that when exposed to too much, can be harmful, such as ultraviolet radiation; an increased exposure to ultraviolet radiation can cause sunburn and increase your risk of developing melanoma and non-melanoma skin cancer. Some people also think that the radiation given off by telecommunication devices could also be harmful, but as yet a number of studies have not identified any health risks associated with these devices.

Which brings us on to ionising radiation; this is commonly used in medical examinations. It is stronger than non-ionising radiation and can therefore cause damage to the cells in your body, which in turn can lead to an increased risk of cancer in later life. The more you are exposed the greater the risk – but these risks are small in comparison to the natural rate of cancer development which is 1 in 3.

The average level of radiation received by the members of the public has been calculated by Public Health England and is measured in millisieverts (mSv). This figure is calculated from a number of sources; naturally occurring radiation in homes and workplaces and naturally occurring radioactivity in food and from medical exposures. (https://www.gov.uk/government/publications/ionising-radiation-dose-comparisons/ionising-radiation-dose-comparisons )

In the UK this number is 2.7mSv.

So, what does all that mean?

We can start by basic comparisons, for example, 100g of Brazil nuts contains 0.01mSv, which is more radiation than you would receive from a dental x-ray (0.005mSv). But this is not as much as you would receive from a chest x-ray (0.014mSv). However, a transatlantic flight (0.08mSv) would expose you to more radiation than a chest x-ray (0.014mSv), because you are closer to the cosmic radiation emitted from the sun.

Screen Shot 2015-09-28 at 12.32.01 PM

Figure 2                                                        

Where does a mammogram fit in this scale of risk? * Somewhere between a chest x-ray and the annual UK radiation dose (2.7mSv).

  1. Q. So, should I go ahead and have a mammogram? Is the risk from radiation still a concern?
  2. The benefit from screening mammography and early diagnosis far outweigh the risk.
  3. But I’ve heard all that before, what does it actually mean?

A.1. A mammogram can save your life! If cancer is found early, you reduce your risk of dying from the disease by 25-30%.

  1. It is the most powerful breast cancer detection tool, BUT, they can miss 20% of cancers. Mammograms work best alongside being breast aware. (www.breastcancer.org )
  2. Lifestyle factors like being overweight and not exercising are far more likely to cause breast cancer than having a mammogram.
  3. Women aged 40-74 who have regular screening have a lower chance of dying from breast cancer than those that don’t (www.cancer.gov/types/breast/patient/breast-screening-pdq ).

To put in to context, we can compare everyday risks and what chance you have of dying as a result of them;

Activity Risk of Death
Smoking 10 cigs a day 1 in 200 per year
Heart Disease 1 in 300 per year
CT Abdomen 1 in 3,600 over lifetime
Natural Background Radiation 1 in 9,000 per year
Accidents in the home 1 in 15,000 per year
Road Accidents 1 in 17,000 per year
Nuclear Discharge 1 in 140,000 per year
Flying to Spain 1 in 1 million per flight over lifetime
Chest X-Ray <1 in 1 million over lifetime

Christie Medical Physics and Engineering – collated from a variety of sources

Examination Effective Dose Lifetime risk of fatal cancer
Chest X-Ray 0.014mSv <1 in a million
Abdomen X-Ray 0.47mSv 1 in 43,000
Barium Enema 2.2mSv 1 in 9,000
CT Chest 6.6mSv 1 in 3,000
Mammogram 0.5mSv 1 in 20,000 per visit (NHSBSP 54)

HPA-CRCE-012 (2008) According to the UK National Office of Statistics:

  • 1 in 3 people will develop cancer at some time in their lives
  • 1 in 4 people will die from cancer
  • 1 in 7 women will develop breast cancer
  • This is the ‘baseline’ or natural risk
  • 170 cancers are detected by the NHSBSP (NHS Breast Screening Programme) for every cancer that is induced. (NHSBSP 54 2003)
  • The mortality benefit of screening exceeds the risk of any damage by radiation by 100:1 (NHSBSP 54 2003)
  • Even if you are the small proportion of women who receive a higher dose, your benefit will exceed the risk by about 20:1 (NHSBSP 54 2003)

Ultimately: Your risk of radiation induced fatal cancer is MUCH LOWER than your lifetime risk of cancer.

Does this help answer some questions relating to radiation dose and having your mammogram? 

What else would you like to know?

 

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