Q&A: Breast screening
The UK pioneered the world's first breast screening programme, aiming to pick up cancers early and offer the greatest chance of cure.
The latest review suggests women should continue to attend screening but that the advice they receive on potential harms should be updated.
What is the breast screening programme and why are there calls for change?
What is breast screening?
Breast screening aims to find breast cancers as early as possible, before people are aware of any symptoms and when the chance of cure is highest.
The NHS Breast Screening programme invites all women between 50 and 70 who are registered with a GP in England to have a special X-ray of their breasts - a mammogram - every three years.
In some parts of the country the programme has been extended to cover women aged 47-73. By 2016 this will apply to the whole of England.
Women over 73 can still attend screening by making their own appointments.
Women who are at high risk, with a known family history for example, are often offered screening at a younger age.
What can breast screening show?
Mammograms can show many different changes to normal breast tissue. Well-developed cancers can show up as lumps or irregularities.
Early cancers can be harder to spot.
Not all cancers show up on mammogram and some changes that do show up are not caused by cancer.
If any changes are spotted on a mammogram you may be invited to discuss these at a breast unit and may have further tests - including biopsies (a small tissue sample taken) - to find out exactly what the changes are.
How is the advice changing?
An independent panel was set up to look at the evidence for breast screening because of concerns women were being told about the benefits of screening but not enough about the possible harms.
One of the main issues the panel were concerned with was overdiagnosis.
What is overdiagnosis?
Overdiagnosis happens when a women has screening and a tumour is spotted and correctly identified as a cancer, but the cancer that is found would not cause her harm in her lifetime or would not be fatal. This could be a very early, slow growing cancer, for example.
Some women in this situation go on to have further tests and treatments that can be distressing and invasive and which would not have been necessary to save their lives.
Why does overdiagnosis happen?
With the current technology, doctors cannot reliably tell whether a breast cancer found through screening is going to be fatal or cause the person further harm. So all women who have cancers identified through the screening programme are offered further tests and treatment.
What did the report find?
Breast screening does save lives. According to the evidence the panel looked at, the breast screening programme means that 1,300 deaths from breast cancer are prevented each year.
But for each death prevented by screening, three women are diagnosed and treated for cancers that would not have been fatal in their lifetimes. This means that every year 4,000 women are diagnosed with cancers that may not have harmed them.
On balance, the report says women should still attend screening but that the advice on leaflets needs to change to reflect the chance that some people may be overdiagnosed.
Current advice does not highlight the scale of risk.
What should you do if you are invited for screening?
Screening is not compulsory and it is up to the individual to weigh up the benefits and risks.
Screening can cut your risk of dying from breast cancer. Current evidence shows that women invited for screening cut their risk of dying from breast cancer by a fifth compared with no screening.
But if you have screening you have to accept the risk you may undergo tests and treatment for a cancer that would not have necessarily killed you.
Some of this treatment may be very distressing and invasive, including surgery and chemotherapy.
On balance, cancer charities such as Cancer Research UK and Breakthrough Breast Cancer recommend that women go for breast screening when invited.
What are the symptoms of breast cancer?
Some people notice lumps in their breasts. Most of these lumps turn out not to be cancer. They may be benign, non-cancerous cysts, for example. But with further tests some lumps are confirmed as cancers.
Women should be aware of what is normal for them so they can spot any changes.
Changes to look out for include lumps or thickening of the breast, dimpling of the skin, changes to the size or outline of the breast, changes to the appearance of the nipples, bloody discharge from the nipples and lumps in the armpit area.
These changes do not necessarily mean you have cancer but it is important to see a doctor if you spot any of these.
What is the treatment?
The treatment for breast cancer depends on many factors including the type, grade and size of the cancer.
Your doctor may want to do more tests to guide treatment.
There are different options, including:
Surgery: Most people with breast cancer have surgery. Early cancer may be taken out with a lumpectomy, leaving the rest of the breast intact.
If the cancer is more widespread the whole breast may need to be removed. This is known as a mastectomy.
Hormone treatment: Some breast cancers may be sensitive to hormones - eg oestrogen. In these cases, treatments based on blocking the action of the hormone may be offered.
Targeted therapy: Targeted therapy looks at whether the cancer cells respond to a group of drugs that block the growth and spread of cancer by interfering with the biology of the cancer cells. The best known of these is the drug trastuzumab (herceptin).
Radiotherapy: May be given before surgery to shrink a tumour or after surgery to prevent the cancer coming back.
Chemotherapy: This is the use of drugs that kill the cancer cells. There are many different drugs that are used depending on the nature of the tumour. They may be given before or after surgery.