In 2011-12, almost two million women aged 45 and over were screened as part of the NHS Breast Screening Programme.
Women who are 50-70 years of age and registered with a GP are automatically invited for screening every three years. You will first be invited for screening between your 50th and 53rd birthday.
If you're over the age of 70, you'll stop receiving screening invitations. However, you're still eligible for screening and can arrange an appointment through your GP or local screening unit.
The NHS is currently in the process of phasing in breast screening for all women in the extended age range of 47-73. The programme started in 2010 and should be completed by 2016.
More details about the extended age range for breast cancer screening can be found on the NHS Breast Screening Programme website.
What happens during breast screening
Breast screening is carried out at special clinics or mobile breast screening units. The procedure is carried out by female members of staff who take mammograms (X-rays of the breast).
The aim of screening is to detect breast cancer at an early stage, when any changes in the breast would be too small to feel and when there's a good chance of successful treatment and full recovery.
During screening, your breasts will be X-rayed one at a time. The breast is placed on the X-ray machine and gently, but firmly, compressed with a clear plate. Two X-rays are taken of each breast at different angles.
Most women find the procedure uncomfortable and can occasionally be painful. However, the compression is necessary to ensure that the mammogram is clear. Any discomfort will be over quickly.
After your breasts have been X-rayed, the mammogram will be checked for any abnormalities. The results of the mammogram will be sent to you and your GP.
Not all breast cancers are found during screening. Breast cancer can develop between screening appointments. Even if you attend your screening appointments, it's still important for you to be familiar with your breasts, so you can spot any unusual changes early and report them to your GP.
Pros and cons of breast screening
Most experts agree that regular breast screening is beneficial in identifying breast cancer early. The earlier the condition is found, the better the chances of surviving it.
You're also less likely to need a mastectomy (breast removal) or chemotherapy if breast cancer is detected at an early stage.
Studies carried out in Sweden and England have shown that more women's lives are saved through breast screening compared with women who are over-diagnosed.
Over-diagnosis is when cancers are picked up and treated that wouldn't have been diagnosed in a woman's lifetime had screening not taken place.
The Swedish study found that in a group of 1,000 women who were screened from the age of 50 over a 20-year period, there were around nine breast cancer deaths compared with four over-diagnoses.
In the English study, which also followed 1,000 women who were screened from the age of 50 over a 20-year period, it was found that there were around six deaths due to breast cancer and about two over-diagnoses.
Taking the results of the two studies together, this represents 9-13% of women's lives saved following breast screening, compared with 4-7% of women over-diagnosed.
Screening may not help if you already have advanced stage breast cancer.
Cancers may sometimes be found that are treated even though they may not have caused any symptoms or become life-threatening.
There's a chance that the results of the mammogram may not be accurate. There are two types of misdiagnosis, known as:
- a false negative result – where you receive a negative (all clear) result, but cancer is present
- a false positive result – where you receive a positive result (cancer present) and go on to have further tests, but there's no cancer
Following screening, about 1 in 20 women will be called back for further assessment. Being called back doesn't mean you definitely have cancer. The first mammogram may have been unclear.
About 1 in 6 women who are called back for further assessment are diagnosed with breast cancer.
During a mammogram, your breasts are exposed to a small amount of radiation (2-5 millisieverts, or mSv).
For comparison, in the UK, a person receives a dose of 2.2 mSv a year from natural background radiation. However, the benefits of screening and early detection are thought to outweigh the risks.
Screening for women at high risk of breast cancer
You may be eligible for breast cancer screening before the age of 50 if you have a higher-than-average risk of developing breast cancer. You may be considered to have an increased risk if you have a family history of breast cancer (female or male) or ovarian cancer.
If you have an increased risk of developing breast cancer, you may have yearly magnetic resonance imaging (MRI) scans or mammograms, depending on your age and your specific level of risk. MRI scans are sometimes used instead of mammograms, because they're better at detecting cancer if you have dense breast tissue.
Genetic screening for breast cancer
After having an assessment at a specialist clinic, you may be thought to be at increased risk of breast cancer due to your family history. This may be because one of the genes that make breast cancer more likely runs in your family. If this is the case, you should be offered genetic counselling before genetic testing.
Genetic counselling is a service that provides information and advice about genetic conditions. It's provided by healthcare professionals who are specially trained in the science of human genetics (a genetic counsellor or a clinical geneticist).
The counsellor will discuss the risks, benefits and limitations of genetic testing with you. They'll also explain how the information found as a result of genetic testing could have implications for both you and your family.
After you've had genetic counselling, a genetic blood test to look for mutated (altered) versions of genes called BRCA1, BRCA2 and TP53 will be offered, because having one of these altered genes increases your chances of developing breast cancer.
If possible, a relative who's already had breast cancer will be tested first, because this will make it easier to find any genetic faults. If a faulty gene is found, other family members can then be tested to see if they have the same gene.
If a close relative isn't available for testing, you should be offered testing yourself if your family history suggests you have at least a 1 in 10 chance of having a faulty gene.
If genetic tests show you have one of these faulty genes, you may be offered regular screening to check for signs of breast cancer. Possible treatments to reduce your risk should also be discussed.
Read our page on preventing breast cancer for more information about treatments to reduce your risk.
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