Monday, July 06, 2009 by: Dr. Julian Whitaker
Anne is a good patient. She sees her doctor for regular checkups, has yearly mammograms, Pap tests, and colon cancer screenings, and she even paid for a full-body CT scan out of her own pocket. She figures she’s doing everything she can to make sure she doesn’t get cancer.
Truth is, Anne is doing nothing to prevent cancer. Although cancer screening is billed as a preventive service that saves lives, the best it can do is detect disease in its early stages, when it is supposedly easier to treat. Nevertheless, every year millions of Americans dutifully line up for their screenings, completely unaware that they may be doing more harm than good.
For more than 15 years, I’ve been warning patients about the downside of mammograms, PSA testing, and the overall concept of cancer screening. It hasn’t been a popular position. Today, however, there’s a small but growing band of researchers, clinicians, and expert panels who are speaking out against the unbridled use of these tests. One of them, H. Gilbert Welch, MD, a professor at Dartmouth Medical School, has laid out very persuasive arguments in an aptly titled book, Should I Be Tested for Cancer? Maybe Not and Here’s Why. In this straightforward and well-referenced book, Dr. Welch raises several concerns about cancer screening.
1. Few People Benefit From Screening
For starters, the majority of folks who are screened receive no benefit. That’s because, despite scary statistics, most people will not get cancer. Let’s look at breast cancer as an example.
According to government statistics, the absolute risk of a 60-year-old woman dying from breast cancer in the next 10 years is 9 in 1,000. If regular mammograms reduce this risk by one-third-a widely cited but by no means universally accepted claim-her odds fall to 6 in 1,000. Therefore, for every 1,000 women screened, three of them avoid death from breast cancer, six die regardless, and the rest? They can’t possibly benefit because they weren’t going to die from the disease in the first place.
If mammograms worked as touted, death from breast cancer would be rare, since three-quarters of American women 40 and older get regular screenings (a total of 33.5 million per year). The modest decline in the death rate from the mid-1970s, when mammography was introduced, through the present can be attributed to factors other than screening, such as changes in treatment and the dramatic decrease in the use of Premarin and other cancer-promoting hormone replacement drugs. It doesn’t take a rocket scientist to figure out that mammograms do not substantially reduce risk of death from breast cancer.
2. The Most Deadly Cancers Are Missed
The flip side is that some people who are screened get cancer and die anyway. Test results aren’t always accurate. Sometimes cancer is there, but it’s missed (false negatives). In the case of mammograms, it could be a question of a poor-quality test or a radiologist who overlooked something. Even experienced radiologists don’t always interpret test results the same, and sometimes they just plain get it wrong.
The most likely reason that cancer is overlooked, however, is due to the nature of cancer itself. The deadliest cancers grow very rapidly. Screening can detect slow-growing cancers in their early stages, but you can see how aggressive cancers could be missed if you’re only looking for them once a year. Depending on the cancer’s growth cycle, it could crop up just months after screening and be far advanced by the time the next test rolls around.