Screening aims to find breast cancers early, when they have the best chance of being cured.

What is breast screening

Cancer screening involves testing apparently healthy people for signs that could show that a cancer is developing.

Breast screening uses a test called mammography which involves taking x-rays of the breasts. Screening can help to find breast cancers early, when they are too small to see or feel. These tiny breast cancers are usually easier to treat than larger ones.

Overall, the breast screening programme finds cancer in about 8 out of every 1,000 women having screening.

Who has breast screening

Each year more than 2 million women have breast cancer screening in the UK. The NHS Breast Screening Programme invites all women aged between 50 and 70 for screening every 3 years. You need to be registered with a GP to receive the invitations. 

In England, the screening programme is currently extending the age range to include women from 47 to 73 years old.

If you are older than 70, you can still have screening every 3 years but you won't automatically be invited. To make an appointment, talk to your GP or your local breast screening unit.

If you are younger than 50, your risk of breast cancer is generally very low. Mammograms are more difficult to read in younger women because their breast tissue is denser. So the patterns on the mammogram don't show up as well. There is little evidence to show that regular mammograms for women below the screening age would reduce deaths from breast cancer. 

Tests used in breast screening

Breast screening takes 2 x-rays of each breast. The x-rays are called mammograms. 

You have one mammogram from above and one from the side on each breast.

After breast screening

You should get your results within 2 weeks. The radiographer can tell you when to expect yours. Most women have a normal reading.

If the results aren't clear

If the x-ray isn't clear enough or shows any abnormal areas, the clinic staff will call you back for more tests. You might need to have the x-rays taken again.

If you are called back

Around 4 out of 100 women (4%) are called back. If this happens, you might feel very worried. Only around 1 in 5 women called back will turn out to have cancer. So out of every 5 women called back, 4 will be fine.

If you are called back because your mammogram showed an abnormal area, you might have a magnified mammogram. This can show up particular areas of the breasts more clearly. These mammograms show the borders of any lump or thickened area. They can also show up areas of calcium (calcification).

Benefits of breast screening

Breast cancers found by screening are generally at an early stage. Very early breast cancers are usually easier to treat, may need less treatment, and are more likely to be cured.

The current evidence suggests that breast screening reduces the number of deaths from breast cancer by about 1,300 a year in the UK.

Women who are diagnosed with breast cancer at the earliest possible stage have a 9 in 10 chance (90%) of surviving for at least 5 years after diagnosis.

Harms of breast screening

Although breast cancer screening can find many cancers early it isn't perfect. There are some risks.

False positives and false negative results

Screening doesn't always find a cancer that is there. So some people with breast cancer will be missed. This is called a false negative result. 

In some women, the test picks up something even though they don't have breast cancer. This is called a false positive result and can lead to anxiety and further tests such as a breast biopsy.

Overdiagnosis and overtreatment

As well as finding cancers that need treating, screening can also pick up breast cancers that won't ever cause any problems.

At the moment it isn't possible to know whether a breast cancer will grow quickly and needs treatment, or will grow slowly, or not at all. So, almost all women diagnosed have surgery to remove the cancer. Many also have radiotherapy, hormone therapy and chemotherapy.

For some women the treatment is unnecessary but at the moment doctors can't tell who needs treatment and who doesn't.

Screening can also pick up changes in the lining of the breast ducts called ductal carcinoma in situ (DCIS). It isn't possible to tell whether DCIS will develop into a cancer or not. So, many women with DCIS also have breast cancer treatments.

A breast screening review in 2012 found that screening leads to around 4,000 women overdiagnosed in the UK each year.

Exposure to radiation

Each mammogram exposes a woman to small amounts of radiation from the x-rays. But the amount of radiation is very small.

If 10,000 women have regular 3 yearly breast screening between the ages of 47 and 73, there will be between 3 and 6 extra breast cancers caused by radiation.

The balance of benefit and harms

15,500 breast cancers are diagnosed through screening in the UK each year. Of these, 4,000 will be overdiagnosed and 1,300 lives are saved.

This means that for every life saved from breast cancer by screening, around 3 women are overdiagnosed.

Screening for women at higher risk

You can have screening from a younger age if you have a higher than average risk of breast cancer. This might be due to a family history or an inherited faulty gene.

Speak to your GP if you think you might be at increased risk. They can refer you to a genetic specialist, who can assess your risk. Not everyone with a family history of cancer is at increased risk themselves.

If you have a family history of breast cancer

UK guidelines recommend that women with a moderate or high risk of breast cancer because of their family history should start having screening mammograms every year in their forties.

If you are younger than 40 and have an increased risk of breast cancer, you should be offered yearly MRI scans from the age of 30 or 40. This depends on your level of risk.

If you have a gene mutation

If you have had tests that diagnosed a change in a gene (mutation) that increases the risk of breast cancer, the recommendations are slightly different.

UK guidelines recommend yearly MRI scans from:

• age 20 for women with a TP53 mutation
• age 30 for women with a BRCA1 or BRCA2 mutation

Should I go for breast screening?

It’s important that you have access to enough information about the benefits and harms of breast screening to make the decision.

Breast awareness

Even if you are having mammograms every 3 years it is important to make sure that you know how your breasts normally look and feel. Many breast cancers are still found by women themselves. Cancers can develop between mammograms. This is known as an interval cancer. Mammograms can also miss some cancers.

If you notice any unusual changes in your breast don’t wait until your next mammogram. See your GP straight away.