Breast screening

Who gets screened for breast cancer?

Breast screening is a way of finding breast cancers early when they are too small for you to feel. Screening is normally carried out by using X-rays called mammograms.

Currently all women registered with a GP and aged between 50 and 69 years are offered screening by X-ray mammography every three years. Women over 69 years are not automatically invited for breast screening but these women can still have free mammograms by making an appointment every three years. Each year approximately one to one and a half million women in the UK attend for screening mammograms. Screening will be extended to include all women from 47 to 73 over the next few years.

What is a mammogram?

A mammogram is a low-dose X-ray of the breast. It is a test to look for early breast cancer.

How is it performed?

To have a mammogram you need to remove your clothes from only the top part of your body including your bra. Each breast is then placed on the X-ray machine in turn and gently but firmly compressed using a flat clear plastic plate and an X-ray image taken.

Benefits of screening

Finding cancer early

Most cancers diagnosed through screening are found at an early stage when there is a good chance that treatment will be successful and eradicate the cancer. In the UK, more than two-thirds of screen-detected cancers are detected at a very early stage, that is they are small and have not spread to the lymph glands.

Over 15 million women have had screening in the UK since the programme started in 1988. In that time over 85,000 cancers have been detected.

Studies suggest that screening saves at least 300 lives every year and by 2010 the number of lives saved each year may be as high as 1,000. Studies also

suggest that, for every 500 women who attend for breast screening, one will have her life saved.

Less treatment is possible

Women who are found to have cancer through breast screening are more likely to have small cancers that can be treated by lumpectomy (removal of the lump) combined with postoperative radiotherapy, also called breast-conserving treatment, rather than removal of the whole breast (mastectomy).

Seventy per cent of women diagnosed with breast cancer through breast screening have breast-conserving treatment compared with 55 per cent of women whose cancer is not detected through screening.

Problems with screening

Not prevention

Screening does not prevent breast cancer. Women who are going to develop breast cancer will do so whether or not they are screened. Screening helps find cancers only if they are already there.

Pain and discomfort associated with having a mammogram

To get a good quality mammogram the breast tissue does need to be compressed (squashed). Many women find mammography uncomfortable or painful but any pain or discomfort lasts for a very short time.

Having mammograms involves more X-rays

Mammograms use only a very small dose of radiation to the breast. The amount of radiation is similar to the dose of radiation a person would receive from flying in an airplane from the UK to Australia and back. The risk from the very low dose of radiation is far outweighed by the benefits of detecting a breast cancer early.

Finding abnormalities in the breast that are not serious

Mammograms can detect a range of benign conditions as well as cancers. A woman who has an abnormal area in the breast detected on a mammogram will need to undergo more tests to show that the abnormality is not a cancer. This means that some women undergo unnecessary tests and have the worry associated with being recalled for these tests for no real benefit.

This happens with any screening programme and is known as a false-positive result. Fortunately it is not very common in breast screening.

Women recalled for extra mammograms when there is no abnormality

Some women are recalled for further mammograms because either the X-ray is blurred or the whole breast was not included on the X-ray. Nowadays, this is extremely uncommon but it is sometimes necessary to call women back to ensure that the X-ray is of sufficient quality.

Breast screening does not detect all cancers

Mammography is the best and most reliable way to detect breast cancer but it is not perfect. Breast cancer can sometimes be missed on a mammogram for a number of reasons:

• Some cancers are very difficult to see on an X-ray.

• Some cancers are there but are very small so they are not large enough to be seen on the X-ray.

• The cancer is present on the X-ray but it is missed by the person reading the mammograms.

Having mammograms every three years is the most cost-effective way of breast screening but, because the three-year gap is quite long, some women will develop breast cancer between one round of screening and the next. If you do have a cancer diagnosed during screening or between screening visits, any mammograms taken previously may be useful to your doctors.

In most cancers diagnosed between screens, when the previous mammograms are looked at there is not a significant abnormality on the previous mammogram and it is a new development, rather than the cancer having been present on the previous X-ray but having been missed by the person reading it.

Overdiagnosis

Some cancers found by breast screening are not of a problem type so that they would never have caused a problem later in life. This means that screening diagnoses cancers in some women when treatment during the patient’s lifetime would never have been needed.

Unfortunately it is not possible to tell which cancers will and which will not spread and cause problems. For this reason it is better when a cancer is detected to treat it effectively even if sometimes this is over-treatment.

Organisation of screening

There are more than 90 breast screening units across the UK. All women receive their first invitation to screening some time between the ages of 50 and 53 and invitations are then sent out every three years up to and including the age of 70 years.

If you receive an invitation from your local breast-screening unit, you will be given a date, time and place to attend. This may be to one of the specialised fixed screening units across the country or to a mobile unit that looks like a large van which is usually in a convenient place such as a car park in a shopping centre.

If the appointment is inconvenient, you can telephone the breast-screening unit and they will arrange an alternative appointment. The phone number will be on the letter.

What happens when I go for screening?

A visit to a breast screening unit usually takes only about half an hour. You will be greeted by a female receptionist or a female radiographer who will check your personal details (name, age and address). The radiographer will ask you some questions about your general health and whether you have had any previous breast problems.

You will then receive an explanation of how the mammogram will be taken. Staff will be very happy to answer any questions that you have about breast screening.

Results from screening

You and your GP should get the results of the mammograms in writing within two weeks. If you do not hear anything within that time you can phone your breast-screening unit and ask them to check your results. Eleven of every twelve women who attend for screening will have a normal mammogram.

About one in twelve women who go for breast screening is asked to come back for further tests. The problem may not be cancer because there are many breast changes that can show up on a mammogram that are not serious. If you are brought back you will be invited to return to an assessment clinic and have further tests.

You will probably experience a range of emotions from anxiety to fear if you are asked to come back for further tests. It is important to remember that in seven

of eight women who are recalled for assessment further tests show nothing wrong or that they have a benign condition. Only one in eight women who come back for further tests will be diagnosed as having breast cancer.

What do mammograms show?

Mammograms show normal breast tissue as white and fat as black. Anything that is abnormal also shows up as white. Cancers are classically extra blobs of white tissue with an irregular margin and are often described as stellate because they look like stars.

In fact, looking for cancers is like looking for stars at night. When the night is very cloudy, as is the situation in young women who have dense breast tissue which shows as white on the mammogram, it can be quite difficult to see stars or cancers even though they are there. When the night sky is clear, as when there is a lot of fat in the breast, which is the situation in older women, it is much easier to see the stars or cancers.

The two main reasons why screening mammograms are usually performed in women over the age of 50 years:

• The incidence of breast cancer increases with age and therefore there are more cancers in older women.

• Cancers are easier to see on the mammograms in older women. In younger women who have more active breast tissue a cancer is usually more difficult to detect.

The main types of abnormality detected through breast screening are:

• rounded masses

• irregular masses

• disturbance of architecture.

Rounded masses

These have very crisp clean edges on the mammogram and show up as an extra white blob that is separate from the surrounding breast tissue. These are most commonly benign lumps such as cysts, which are fluid filled, or fibroadenomas, which are solid, benign, localised overgrowths of breast tissue. About four per cent (4 in 100) of rounded masses turn out to be cancers.

Irregular masses

These also show up as white blobs on a mammogram. However, their edges on the mammogram are much more fuzzy and irregular. The majority of new irregular masses are cancers.

Disturbance of architecture

This is one of the most difficult abnormalities to detect. The breast tissue is pulled in around a central area so that the breast tissue around it looks distorted.

Disturbances of architecture can be benign and occur as a result of scarring or can be malignant with a cancer in the centre. Needle biopsies cannot always tell

the difference between distortion caused by scarring or distortion caused by a cancer and it may be necessary to remove the area to be certain of the cause of the abnormality.

Calcifications

Small areas of calcium are common in the breast and they are often seen on mammograms. In most cases they are harmless. There are two types of calcification:

• Macrocalcifications

• Microcalcifications.

Macrocalcifications

Macrocalcifications are larger, coarse, calcium deposits in the breast that appear as white dots or dashes on a mammogram. They are the natural result of breast ageing and are found in about half of women aged over 50 and one in 10 younger women.

They may be caused by calcium deposits in cysts or by calcium building up in the milk ducts in the breast. They can also occur as a result of previous injury, surgery or radiotherapy.

These calcifications are not related to how much calcium is included in your diet. They are harmless, are not linked with cancer and do not need any treatment.

Microcalcifications

These are tiny deposits of calcium that show up as fine white specks on a mammogram. Similar to macrocalcifications, they can occur because of the ageing process in the breast, but they can also occur as a result of cells growing more quickly than normal. Usually microcalcifications are not the result of cancer.

If the microcalcifications vary in shape and size, line up within the milk ducts of the breast and have a branching pattern, these are indications that the calcifications might be the result of overgrowth or early cancerous change of the cells lining the milk ducts.

Microcalcifications seen close together or in clusters are a sign that there may be precancerous changes (see Ductal carcinoma in situ, page 68) in this area of the breast.

If microcalcifications are seen, you will usually be asked to have a further mammogram to look at the area in more detail (magnification mammogram). Depending on the result of this mammogram the doctor will either recommend taking no further action or advise a needle core biopsy, which involves taking a sliver of tissue from the area to remove part of the calcification so that this can be examined under the microscope (see page 53).

The problem is that a core biopsy removes only a very small amount of tissue and sometimes insufficient calcification is sampled and further tests are needed. Areas of calcification can be sampled adequately by using a slightly larger needle with suction, to suck breast tissue into the needle.

These vacuum-assisted biopsy devices remove more tissue and are easier for women because the needle has to be inserted only once into the breast. If despite all the needle tests the doctors fail to get enough calcification to be certain what is causing it, the area may need to be removed by surgery.Women are offered breast screening with a breast X-ray every three years between the ages of 50 and 69.

KEY POINTS

• Breast screening aims to find cancers early when less aggressive treatment may be needed

• Breast screening may find changes in the breast that are not serious but need extra tests to be sure that the changes are benign and not cancerous

• Breast screening may find abnormalities in the breast that are precancerous (known as DCIS or ductal carcinoma in situ) which if left alone in the breast change into cancers over many months or years