Mammograms in breast screening

• A quick guide to what's on this page
• What a mammogram is
• What happens when you have a mammogram
• How a mammogram feels
• What happens after the mammogram
• If you are called back
• What a mammogram can show
• Very early non invasive cancers - DCIS
• Possible risks of breast screening
• Breast screening, overdiagnosis and overtreatment
• Anxiety about screening

A mammogram is an X-ray of the breasts. The NHS breast screening programme uses them to screen for breast cancer in women between 50 and 70 in the UK. The Government is planning to expand the breast screening programme to cover women between 47 and 73 by 2012.

The 2006 breast screening report estimates that UK breast screening now saves 1400 lives each year. For every 400 women screened over a 10 year period, one less woman dies from breast cancer than if they had not been screened. This means that 1 in 8 fewer women between 50 to 70 years of age die from breast cancer. So, many doctors and researchers feel that breast screening saves lives and is cost effective.

A radiographer helps you to position one breast at a time on a small flat plate, with an X-ray plate under it. There is another flat plate above your breast. When the machine is switched on, your breast is pressed down between the plates by the machine for a few moments. The compression of the breast helps to give a clear picture of the breast tissue.

Women in the UK have 2 pictures taken - one from above and one from the side. This gives a higher chance of picking up changes in the breast tissue that could be due to a cancer. Researchers have shown that taking a 2 view mammogram each time increases the breast screening programme's cancer detection rate by 25% to 45%. So, more women have their cancers found early when they are easier to cure.

It isn’t surprising that women worry about whether a mammogram will hurt. For some women it is just uncomfortable. But it really depends on your breast size and pain threshold. Some women do feel some pain, but it is only for a few moments while you are having the test. 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. They found that using breast cushions during the mammogram could reduce pain but can also make the mammogram less clear. 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 so is not in plain English.

Two radiologists look at your mammogram to see if there are any signs of cancer. You should get your results within 7 to 14 days. In very busy clinics, this can take longer, so don’t worry if you don’t hear for up to 4 weeks. If there is any doubt at all about your mammogram, the clinic staff will call you back for more tests.

There is no reason to worry if you are called back for more tests. About 1 in 20 women (5%) are called back as part of the UK breast screening programme. But only 1 in 8 of these women will turn out to have cancer. That's only about 7 out of every 1,000 women having breast screening.

So out of every 8 women called back, 7 will be fine. These women will have had some unnecessary anxiety. But doctors and researchers feel that the anxiety for these women is balanced by the success of the screening programme in picking up many breast cancers very early on in their development. Very early breast cancers are usually easier to treat, may need less treatment, and are more likely to be cured.

Well developed breast cancers nearly always show up clearly on mammograms. Unfortunately, there will always be some that are missed or do not show up. No medical test is perfect, but the screening programme organisers do make every effort to pick up as many cancers as possible.

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.

Your screening mammogram may show DCIS. This stands for 'ductal carcinoma in situ'. It means that there are changes in the cells lining the breast ducts. The breast cancer cells are only inside the ducts of the breast. The ducts are the tubes that carry milk within the breast. In some women DCIS may spread into the surrounding breast tissue after some years, to become an invasive ductal breast cancer.

Because they haven't broken out of the ducts, the cancer cells can't have spread to the lymph modes or other parts of the body. So there is very little risk of DCIS coming back once it has been removed with surgery.

As with all X-rays, having a mammogram exposes you to some radiation, but only a small amount. Scientists have worked out that there is less than a 1 in 25,000 risk of a mammogram causing breast cancer. About 7 breast cancers are found for every 1,000 women screened as part of the UK breast screening programme. And in these women the cancers are generally at an earlier stage, when it is more likely to be curable. So, doctors and researchers generally think the benefits of finding breast cancer early far outweigh the small risk of radiation from screening mammograms.

Some doctors have been concerned that some women have changes on mammograms that are not cancer but they have to have further tests to show that it is not a cancer. The tests can cause worry and can be uncomfortable (such as a biopsy).

Screening can also find some very early, slow growing breast cancers that would never cause any problems in a woman's lifetime. Because we can't tell which are the slow growing ones, some women have unnecessary mastectomy. Some doctors feel that this is a big problem. But the UK breast screening programme results estimate that about 1 in 8 women who have screening have a lumpectomy instead of mastectomy because their breast cancer is found so early. So, although screening may increase the rate of mastectomy in one group of women it greatly lowers the mastectomy rate for other women.

Screening may also pick up some cases of DCIS that wouldn’t get any worse if they were left alone. Cancer Research UK researchers estimate that up to 1 in 3 cases of DCIS found by breast screening might not develop into invasive cancer if they weren’t treated. We can’t really know for sure which ones those are, or how many women are affected. As we can’t tell at the moment which types of DCIS are going to carry on developing into an invasive cancer, the safest option is to treat them all. So some women with DCIS may have unnecessary treatment.

So some women may be having surgery they don’t need, but many more will be having potentially life saving treatment. All we can do is continue research into finding out more about how to identify types of DCIS that won’t develop into cancer. We are learning more about the different grades of DCIS and that should help in the future. A clinical trial is currently looking into the detection and treatment of DCIS. While it is open this tral will be listed on our clinical trials database. Type 'DCIS' into the free text search box.

Some people say that the screening programme causes unnecessary anxiety and distress for the 7 out of 8 women called back for more tests who turn out to be fine. But this needs to be balanced against the fact that the programme diagnoses breast cancer early for many women and so saves them and their families much more distress. This is a decision that we all need to make for ourselves. Many women find having regular breast screening very reassuring, knowing that it is very likely to pick up cancers at an early stage when treatments work best.