Chance News 12
From the doctors' perspective, early detection has other appealing features: ordering a test is quick and easy, and it has an established billing process--unlike health promotion counseling.
--H. Gilbert Welch<\blockquote>
One thing almost all people know is that it is prudent to be screened for diseases because that will add to their longevity. However, according to H. Gilbert Welch, a medical doctor at Dartmouth College, it isn't necessarily so.
His book, Should I Be Tested For Cancer? Maybe Not And Here's Why [University of California Press, 2004], focuses on screening which is a particular form of testing and he deals exclusively with cancer as opposed to other afflictions. Screening "means the systematic examination of asymptomatic people to detect and treat disease." His contention is that screening for cancer is inefficient in that very few people who actually have the particular cancer are both discovered and then cured. Moreover, the false positives result in many problems of which the general public is not aware. On the other hand, false negatives of cancer screening are barely mentioned in his book "because we do not biopsy people with negative screening tests." That is, we can't distinguish between a false negative and a rapidly-growing cancer that emerges in between screenings.
In a nutshell, randomized clinical screening trials for those cancers discussed in the book--lung cancer, cervical cancer, breast cancer, prostate cancer and colon cancer-- have statistically shown that screening has provided very little benefit in terms of mortality. Welch argues that with the new, exquisite devices such as CAT scans, MRIs, etc., now available, it is possible to detect cancer earlier so that it seems that the 5-year survival rates have improved; victims are living longer not because the treatments are better but only because the diagnoses were made earlier. Further, these devices are detecting what he calls "pseudodiseases," cancers which will never develop into a cancer that will cause a problem. It follows that this detection of cancers which would never have been discovered years ago when there was a lack of technology, further inflates the 5-year survival rate, a figure of merit which he would like to see abolished because it is so misleading.
He argues that the side effects of a false positive are not to be taken lightly. Chapters 2 and 3 are entitled "You may have a cancer 'scare' and face an endless cycle of testing" and "You may receive unnecessary treatment," respectively. Certainly, in bygone days being told that you had cancer was frightening in the extreme. Perhaps not so much in these enlightened times, but a stay in a hospital, especially for an unnecessary procedure, can definitely lead to unpleasant side effects such as infection or worse.
Welch points out that there are vested interests in the screening industry: doctors, hospitals, clinics, insurance companies and lay organizations which depend for their existence, financial and otherwise, on keeping Americans fully screened and uninformed on the problems with screening. For example, although it has been statistically shown via randomized clinical screening trials that mammography, an unpleasant procedure at best, is not useful for women under 50, the "mammography lobby," made up of manufacturers, radiologists, ideologues and feminists who considered the studies to be a male plot, went ballistic and wanted to substitute emotion for science: The National Cancer Institute reconsidered and by 17 to 1 decided "in favor of recommending mammography to all women in their 40s."
The same sort of situation applies to prostate cancer. The accepted, conventional wisdom in the United States is that screening must be worthwhile because it is self-evident even though a careful look at the data points in the opposite direction. Watchful waiting, a much used medical treatment in Europe for prostate cancer is frequently ridiculed in this country by both laymen and urologists.
Welch fully realizes his thesis--screening for most cancers is, by and large, ineffective and/or harmful--will not go over well because it "flies in the face of medical dogma." His "book is not about what to do if you know you have cancer; it is about informing the decision of whether to look for cancer when you are well." This distinction has been lost on the people I have spoken to. The conventional wisdom that cancer screening must be desirable is a notion that, as far as I can tell from my experience when discussing it with others, is unchallengeable. To be even more cynical, any doctor who doesn't order a screening test for a patient who eventually gets cancer is likely to be sued successfully, so ingrained is the conventional wisdom among the general public and judges alike.