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Breast Screening in Young Women
The death of the Girls Aloud singer, Sarah Harding, from breast cancer at the age of 39 understandably raises the question as to why young women are not called for breast screening. The answer is not straightforward.
Let’s start by looking at what a screening test is
A screening test takes a group of people with no symptoms and looks to see if it can find evidence of a disease before it would normally be detectable. The rationale is that by picking up a disease at an early stage treatment is more likely to be effective. It should detect a disease with serious consequences and there’s no doubt that breast cancer fits the bill here.
In the NHS breast screening with mammograms starts at the age of 50 (in some areas this may be 47) and is carried out every three years until the age of 70. This is the population where most breast cancers can be detected with, what is called, the greatest “cost benefit” (yes, with the NHS it all seems to come down to what is affordable, in the end). I think it would be fair to say that most people feel that 50 is too late to start and that 3 yearly is too far apart. Screening every year from 40 would not be inappropriate, and there is no logic to stopping at 70 as breast cancer becomes more common with advancing age.
For a screening test to be a good one there needs to be a high incidence of the disease in the population that is screened. A good screening test should be able to accurately detect the disease.
Mammograms not effective for women under 40?
Breast cancer is very uncommon in women under 35. Only 5% of cases occur in this age group with most breast cancers affecting women after the menopause.
Additionally, young women (generally) have dense breast tissue. This means that breast cancer is harder to detect with mammograms (the standard screening test) which will miss a higher proportion of cases (we say that in younger women it has a low sensitivity).
Moreover, there will be what is called a high false positive rate, where women who do not have breast cancer will be subjected to, often potentially harmful, tests to prove there is nothing wrong (we say mammograms have a low specificity).
The combination of the low incidence of breast cancer in younger women, coupled with the low sensitivity and specificity of mammograms in this age group means that for the general population of women under 40, breast screening is not effective.
That still leaves us with the question as to what we can do for younger women. Certainly, for women in the general population, under 40, with no breast symptoms, no one should be doing mammograms. But what if we can find a group of younger women within the general population where the risk of breast cancer is much higher?
Family history could link to Breast Cancer
One such group is women who have a significant family history of breast cancer. If a woman’s mother sister or daughter has had breast cancer (we call these first-degree relatives) then their own risk is increased. If two have been affected the risk is higher. In some of these cases there will be an abnormality in a gene that can significantly increase the risk of breast (and ovarian) cancer.
The two most well-known genes are called BRCA1 and BRCA2 (because abnormalities in these genes are known to cause a significant rise in the risk of developing breast cancer, we might call these “major” breast cancer related genes), but we know of many others that have a lesser, but still measurable, effect (we call these “minor” breast cancer related genes).
In such cases breast screening can be carried out because of the higher incidence in this selected group, starting at the age of 30. Remember that mammograms are not particularly good under the age of 40, so from 30 to 40 MRI scans are used and these are done every year. From 40 to 50 women will have MRI scans and mammograms yearly and then, after 50, annual mammograms, with MRI scans added if the mammogram suggests a potential problem.
Benefits of early genetic testing
To find out if your family history is such that you might benefit from early, more regular breast screening, or if there might be an abnormal gene in your family, you would usually be assessed by an expert in genetics. The NHS runs “Family History” clinics for this purpose but the criteria for being seen can be quite restrictive.
Here at 108 Harley Street our Consultant Genetic Oncologist, Dr James Mackay can arrange to see you to discuss your family history and arrange genetic testing, if it’s appropriate. He can test not only the “major” genes, but also the “minor” genes and look for other patterns in your genes that might affect breast cancer risk (technically these are known as “single nucleotide polymorphisms”!) so that for each woman he can work out an individual screening strategy which can then be followed with our team of radiologists and breast consultants.
Higher risk of breast cancer, among those who have had treatment for lymphoma
Another group of women to mention, who are higher risk of breast cancer, are those who have had treatment for lymphoma (cancer of the lymph glands, for example Hodgkin’s Disease) that involved having radiotherapy to the chest (this is called “mantle” radiotherapy) under the age of 30. The NHS should have a record of these ladies so that they are automatically placed on an early screening program. Screening would start at 30, or 8 years after the treatment started, whichever is the later. The screening is carried out in the same way as for those with abnormal genes or a strong family history. We also know of a small number of genes that not only increase the risk of breast cancer but also make women very sensitive to x-rays (for example the TP53 and the A-T genes). These women should not have mammograms (which are x-rays, albeit low diose x-rays) and so will have annual screening with MRI scans. In these very rare cases, MRI scans might start at 20, or 25.
So, for the general population of women under 40 who do not have any symptoms, breast screening is not appropriate, and mammograms are not (usually) helpful. For those women who have an increased risk of breast cancer, perhaps because of their family history or previous radiotherapy treatment, breast screening is done using a combination of mammograms and MRI scans.
Remember that “screening” applies to people with no symptoms, and if you notice any changes in the breast (then you have “breast symptoms”) you should consider seeing a breast specialist. In women under 40 the standard imaging test will be an ultrasound scan, after examination by the consultant. If it’s new, different, or a bit odd, please get it checked.