The sacred and overly screened female breast - new recommendations rightly recommend discontinuing screening mammograms in younger women.

The United States Preventive Task Force recently released its latest guidance on screening healthy women for breast cancer. To general astonishment the Task Force recommended that mass screening for breast cancer in healthy women between the ages of 40 ad 40 be stopped, along with efforts to teach women to regularly palpate their own breasts, searching for lumps and bumps.

Image Ductal Carcinoma in Situ From - Breast Cancer.org

The Task Force, an unbiased group of experts in cancer screening, epidemiology and disease modeling of effectiveness determined that the potential benefits were slim and greatly outweighed by the very real harms.Public and political reaction to the announcement was immediate, appropriately embedded in current socio-political narrative of women’s health and widely dismissive of science and evidence: Responses were irrational and often personal - claiming that the members of the Task Force were ‘Bush appointees’.  

I have sympathy for a cult that celebrates an organ which is both a procreative and nourishing. I too would wish it no harm: The point of the Task Force recommendation, however, is that screening for small cancers in the breasts of women between the ages of 40 and 49 years is harmful. How can this be so?

Harms and benefits need to be considered together. It is a rare human environments that sees benefits without risks or harms. For breast cancer, the benefits are often tritely and misleading summed as ‘curing’ cancer. Breast cancer advocates regularly proclaim that breast cancer can be cured, beaten, vanquished, extinguished, destroyed, survived. There are testimonials. But what exactly is a cure?

Common sense has it that ‘cure’ means the particular disease has been eliminated and will never, ever, ‘come back’. We don’t know that for sure about breast cancer, or indeed about almost all cancers. We do know that some women with breast cancer live a long time with the disease and it does not seem to bother them very much. Others suffer greatly and live only a short time. These women can have what appear to be similar types of breast cancer when they are first diagnosed.

Scientists and rationalists, therefore, don’t use the word ‘cure’: They use ‘survival’ and survival rates. What is measured is survival after diagnosis for say 5 or 10 years. Thus we can measure the effects of different treatments including screening with mammography for breast cancer in metrics of 5 or 10 year survival rates. It appears true that the 10 year survival rates for women aged 50 to 69 who are screened by mammography for breast cancer are slightly more likely to still be alive and less likely to die of breast cancer in the 10 years after screening than women who are not screened. This is not cure necessarily (and usually isn’t), but it is an improved chance of survival.

These ‘odds’ are often expressed as the number of women who would need to have a mammogram and the associated treatments if the mammogram was positive in order that one woman’s life would be extended. For women aged 40 to 49 this number is 1,904. This means that 1,904 women would have to be screened in order for 1 woman to benefit from the screening. Looked at this way we can say that 1,903 women would have had an unnecessary mammogram.

How can a mammogram be harmful? There are several harms that are relatively trivial and can be ignored - the hassle of getting the mammogram, the discomfort of the procedure, possible anxiety while waiting for the result. But there are others that are more serious.

First, there are the false-positive mammograms. The mammogram shows a potential lesion and there is then a biopsy or lumpectomy that turns out to be negative for cancer. Both procedures are more than trivial and the latter may deform the breast.

Secondly, and most importantly, by far the most common type of cancer detected is called a ductal carcinoma in situ (DCIS). The cancer is classified by looking at it under a microscope. Almost all cancers detected by mammograms are of the DCIS type. We don’t in fact know much about this type of ‘cancer’. But it is clear that many of these cancers spontaneously revert to normal with no treatment.

Unfortunately we don’t know how to separate those that require treatment fro those that don’t. So the standard practice is to treat them all as malignant (even though we know that most are not). The harms associated with treating a benign tumour are unnecessary surgery (which is often deforming) and the associated chemotherapy and radiotherapy. There is also real anxiety that persists for years and decades of follow-up visits to check for spread of the tumour. Cancer is not a trivial diagnosis.

Difficult decisions are always difficult.

The Task Force could have sidestepped this decision by simply presenting the information - the data - and leaving it to the woman to assess risk. But it didn’t. The Task Force, recognizing that such a decision is all but impossible on individual grounds, made a clear recommendation - for the average woman aged 40 to 49, the odds of improved survival from breast cancer that come from mammography are so small and the odds of having to go through unnecessary surgery and radio/chemotherapy so large that most women in this age group should not have mammograms.

The implications of this recommendation are multiple. First the recommendation ought to mean that as a society we cease to promote mammography screening for women aged 40 to 49. Promotion means organizing screening programs and advertising and promoting them. The evidence indicates that such promotion puts 1903 women at risk of harm in order to possibly prolong the 5 or 10 year survival of 1 woman.

To my mind the Task Force has it right. For the average woman aged 40 to 49, mammography is harmful and should be avoided. Individual women and their physicians might decide otherwise, based on other factors such as family history: But as a public mammogram screening program promising that benefits outweigh harms is a misleading and itself harmful.


Reference:

The Natural History of Invasive Breast Cancers Detected by Screening Mammography
Arch Intern Med. 2008;168(21):2311-2316. get article