Mammograms in breast screening
A mammogram is an X-ray of the breast.
The NHS breast screening programme uses mammograms to screen for breast cancer in women in the UK from the age of 50 to 70. Women over 70 can request screening every 3 years by contacting their local breast screening unit. In England, the programme is currently being expanded and will offer mammograms to women between the ages of 47 and 73.
The current evidence suggests that breast screening reduces the number of deaths from breast cancer by about 1,300 a year in the UK.
Having a mammogram
A radiographer helps you to position one breast at a time between two small flat plates on the X-ray machine. The plates then press your breast firmly between them for a few moments, to take the X-ray. The compression of the breast helps to give a clear picture.
You have 2 X-rays of each breast – one from above and one from the side.
How a mammogram feels
Some women worry about whether a mammogram will hurt. For most women it is just a bit uncomfortable. Some women do feel some pain, but it is usually only for a few moments while you are having the X-rays taken. Some women may experience discomfort or soreness for a few days after having the mammogram.
A Cochrane review carried out in 2008 reported that having good information before the test and having control over your breast compression during your mammogram reduces pain. Taking aspirin or paracetamol before the procedure didn’t help. If you would like to, you can read this review on pain in mammography in the Cochrane Library. It is written for researchers and specialists and so uses complex language.
After the mammogram
Two people called film readers or image readers look at your mammogram to see if there are any signs of cancer. The film readers are radiologists or radiographers.
You should get your results within 14 days. The radiographer should tell you when to expect yours. If the X-ray is not clear enough or shows any abnormal areas, the clinic staff will call you back for more tests. You may need to have the X-rays taken again.
What a mammogram can show
Well developed breast cancers nearly always show up clearly on mammograms.
But no screening test is perfect and unfortunately there will always be some cancers that are missed or do not show up.
With early stage breast cancer, there may be no lump, but your mammogram may show small areas of calcium in particular patterns within the breast tissue. These areas of calcium are called calcification. But calcification can also sometimes occur due to non cancerous changes in the breast. The skill and experience of the technicians and doctors helps them to read the different patterns and decide which might be due to cancer and so need further tests.
Some cancers do not show these clear signs on the mammogram. So, if you find any suspicious lump in your breast, always tell your doctor, even if you recently had a mammogram.
Possible risks of breast screening
As with all X-rays, having a mammogram exposes you to some radiation, but only a small amount. For every 10,000 women who have regular 3 yearly screening between the ages of 47 and 73, experts estimate that there will be between 3 and 6 extra breast cancers caused by radiation.
Breast cancers found by screening are generally at an earlier stage, when they are more likely to be curable. So, doctors and researchers generally think the benefits of finding breast cancer early outweigh the risk of radiation from screening mammograms.
Breast screening, over diagnosis and over treatment
Screening can also find some very early, slow growing breast cancers that would never cause any problems in a woman’s lifetime. It may also pick up some cases of DCIS that wouldn’t ever develop into cancer. But doctors can’t tell which early breast cancers or cases of DCIS would never cause a problem. So the safest option at the moment is to treat them all. This means some women have breast cancer treatment that they wouldn’t have ever needed if they hadn’t been screened. Doctors call this overdiagnosis or overtreatment.
A panel of experts reviewed the evidence on overdiagnosis in breast screening in 2012. They estimate that about 4,000 women each year have treatment for a breast cancer that may never have actually caused them any harm. This is out of about 15,500 breast cancers diagnosed through screening annually.
Anxiety about screening
The screening programme can cause unnecessary anxiety and distress for the 4 out of 5 women called back for more tests who turn out to be fine. This needs to be balanced against two things. The programme diagnoses breast cancer early for many women saving them and their families much more distress. But it also overdiagnoses some women who have a breast cancer that would not go on to cause them any problems.