Why do the media’s breast cancer stories come all at once?
This week, for example, you may have noticed an increased number of stories on mammography. The reason? The annual Radiological Society of North America meeting is going on.
This also might be why all the stories seem to be in support of mammography. My favorite were the articles about a study that found that women aged 40 to 49 who did not have a family history of breast cancer were as likely to receive a breast cancer diagnosis as were women with a family history. According to the researchers, this meant that all women needed to have annual mammograms starting at age 40.
What the reporters failed to grasp was that this study was a review of the experience of one mammography center. The researchers looked at all of the cancers that they had diagnosed over the past 10 years in women aged 40 to 49, and they found that 61 percent had no family history of breast cancer while 39 percent did. But based on this one study, we can’t come to the conclusion that we should screen all women over 40. Their findings could mean many things. It might be that women who have mammograms between 40 and 49 have other risk factors for a diagnosis such as radiation exposure at a young age or a lump that they are worried about or a previous diagnosis of a precancerous lesion that needs to be monitored.
The key question is this: Why did they go for a mammogram in the first place and did it make a difference? Answering that question would require a different kind of study that randomizes women and follows them prospectively.
Instead of getting good information we got the message that we should be afraid, very afraid! No one pointed out that the risk of getting breast cancer over ten years is 1 in 69 at age 40! The real conclusion we should take from this study is that we need to find the cause of breast cancer in the few but unfortunate women who develop the disease rather than try to find it after the fact!
Beware: Next week is the San Antonio Breast Cancer Symposium. This very large annual meeting brings together an international group of scientists, drug companies, physicians, and advocates to talk about the latest research, products, and devices. Drug companies and researchers have already begun sending the media lots of press releases about findings that will be presented, But it is often hard to distinguish the wheat from the chaff, and the media often report them without critique or explanation. I will be blogging from the meeting, so be sure to check back for some insider insights as well as guidance on how to interpret all of this information. Meanwhile, make sure as you read the multitude of stories that you remember to ask the key questions:
1. Was the study done on women or animals or cells? Research on rats can give important insights but does not always translate into breakthroughs in women.
2. How many subjects were in the study? The more the better.
3. Was the study randomized and controlled? Did they randomly assign people to the different groups? Observational studies that report retrospectively can show interesting findings but also include biases. For example, the finding that all drug addicts drank milk as babies does not mean that drinking milk causes drug addiction.
4. Was the study conducted in an environment that mimics real life? If it only occurs in a laboratory or in people who are not taking any other drugs, etc., it may be interesting but not useful.
5. Who paid for the study? Industry-sponsored trials can still be valid but the data is often presented with a slant to serve their goal.