Overdiagnosis poses challenges.
|Publication:||Name: Townsend Letter Publisher: The Townsend Letter Group Audience: General; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2010 The Townsend Letter Group ISSN: 1940-5464|
|Issue:||Date: August-Sept, 2010 Source Issue: 325-326|
|Geographic:||Geographic Scope: United States Geographic Code: 1USA United States|
The debate about cancer overdiagnosis continues. Cancer
overdiagnosis refers to the detection of slow-growing tumors that in
themselves will not cause harm; but people who undergo treatment for
them are exposed to possible complications and potential harm from the
treatment itself. As more people obtain screening and the screening
devices become more sensitive to finding abnormalities, cancer diagnoses
have also risen. At this point, however, medical science cannot
distinguish between cancers that are dangerous and those that are
harmless. For this reason, some researchers are suggesting that
practitioners and patients take a little time to see if a tumor is
actually growing before jumping into potentially harmful treatment.
Even though diagnoses have increased over the past 30 years, mortality rates for five cancers have changed very little, according to radiologist William Black, MD, and physician-researcher H. Gilbert Welch, MD. This observation has made the Dartmouth-Hitchcock Medical Center researchers take a close look at overdiagnosis. Recently, Welch and Black reviewed data from large randomized screening trials to estimate the extent of overdiagnosis. Their article appears in the Journal of the National Cancer Institute (April 22, 2010; this journal is published by Oxford University Press and is not affiliated with the National Cancer Institute.) The doctors estimate that overdiagnosis is present in 25% of breast cancers detected on mammograms, 50% of lung cancers detected with chest X-rays and sputum tests, and 60% of prostate cancers detected with prostate-specific antigen (PSA) tests. By definition, patients who are overdiagnosed (that is, who have slow-growing, nonlethal tumors) are going to have long survival rates--whether or not they receive treatment. The inclusion of overdiagnosed patients in clinical trials, says Black in an article by Jennifer Durgin, can make a treatment seem more effective than it actually is.
Neither Black nor Welch is advocating the abandonment of cancer screening, particularly if a patient has a higher risk of getting the disease; however, they and other physicians, including Lisa Schwartz, MD, and Steven Woloshin, MD, do criticize the ubiquitous scare tactics and peer pressure messages that promote universal screening. These messages cause unnecessary anxiety, ignore personal preference, and prevent dialog that leads to informed consent. "Our main point," says Black, "is that there are pros and cons and none of them, none of the screening tests, is a slam dunk in terms of producing a lot more good than harm." Schwartz, who codirects the VA Outcomes Group with Welch, says that overdiagnosis is a factor in any disease associated with early screening, including heart disease and osteoporosis.
Durgin J, Are we hunting too hard? Dartmouth Medicine. Summer 2005. Available at: http://dartmed.dartmouth.edu/summer05/print/hunting.php. Accessed October 23, 2006.
Magnitude of overdiagnosis in cancer indicates need for strategies to address the problem [press release]. Science Daily. April 22, 2010. Available at: www.sciencedaily.com/releases/2010/04/100422170145.htm. Accessed May 19, 2010.
briefed by Jule Klotter
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