The problem is, that whilst it gives some simplified information, it doesn't give women the whole picture. There's not enough information to make in informed choice.
The NHS breast screening program was introduced in 1988 (strangely at the same time as cervical screening was introduced, which is an interesting coincidence).
How has the incidence of breast cancer changed since it was introduced?
Let's have a look at the data:
So screening doesn't affect how many women get breast cancer, as it can't look for "pre-cancerous" cells, it can only detect cancer once it has developed to some degree. It doesn't stop you from getting breast cancer.
So what was the effect on mortality from breast cancer? Does finding it early increase your chance of survival?
Ok, so the short answer is yes. After 1988 there is a clear drop in the number of women dying from breast cancer. It looks impressive as a graph, but let's look at the absolute risk of dying from breast cancer.
Around 1988, 60 women per 100,000 were dying of breast cancer. That's a 0.06% risk. By 2016, that risk has declined to ~34 women per 100,000. That's a 0.034% risk. So the actual decline in risk is 0.026%.
The decline is of course due to early detection and treatment, so what's the harm?!
That is, of course, a good question.
As you'll see in my earlier posts, all screening tests have a sensitivity level, and a specificity level. These numbers indicate the chance of true positives, false positives, true negatives, and false negatives.
Instead of crunching the numbers myself, I'll post a figure from a respected medical journal:
So this shows that for every 1000 women screened over the course of 20 years, 200 will be incorrectly told that they have breast cancer, of those 200, 20 will also have a biopsy to rule out cancer.
3 will develop cancer anyway, either because it was missed in the mammogram, or a fast growing tumour grew between screening periods enough to cause symptoms (interval cancers). A previously negative mammogram might also cause women to assume they're "safe" and ignore symptoms.
15 out of the 1000 women will actually be treated for cancer that they don't have, with lumpectomy, mastectomy, radiotherapy, chemotherapy etc.
Only 2 breast cancer deaths will be prevented per 1000 women, but overall no deaths will be prevented. Why? Treating breast cancer, can cause other issues like heart problems, and you're killed by the treatment.
Another issue is that of finding cancers that, whilst definitely cancers, wouldn't cause you problems in your lifetime.
This is especially true for older women who would likely die from another condition (heart disease etc.) long before their breast cancer would kill them.
So, should you get screened? As always, it's your choice!
Inform yourself of the benefits, and risks, and make the decision based on your own personal situation.
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