Major media has largely ignored the potential harms of cancer screening. The WSJ wisely addresses it:
While it may seem like a no-brainer to get a lung scan to find cancer early, it isn’t clear whether doing so will prolong your life. As a result, patients need to be aware of the risks of the screening procedure itself. One concern is radiation exposure. Each low-dose lung CT scan exposes you to about a year’s worth of ambient radiation, which is the radiation we are exposed to every day from our environment. A one-year dose isn’t much, but if a patient decides to undergo annual screening for 20 years, the numbers can add up.Another concern is a false positive. False positives can range from 10% to 50%. This means a radiologist sees something on your scan that looks like cancer but isn’t. If that happens, you may need additional scans and in some cases, a lung biopsy for benign growths. About 10% of the time a biopsy can result in a collapsed lung or other complications.
The biggest risk of scanning is unnecessary surgery. Some experts think many of the lesions found on CT scans look like cancer in the biopsy, but they don’t act like cancer — meaning they aren’t aggressive and don’t spread. The problem is that it is impossible to tell the difference between aggressive and nonaggressive cancers and so they are all removed, along with a big portion of the patient’s lung. In one recent study, the chance of a patient undergoing a lung resection went up 10 times if he or she was screened.
With the recent flurry of similar blog posts, you may think that I’m against cancer screening. Not true. I most definitely support evidence-based (i.e. studies showing a mortality improvement) cancer screening. Too many stories recently, such as breast MRIs and chest CTs for lung cancer, falsely hype tests without the benefit the evidence behind them. Doctors that don’t present a balanced view do their patients a disservice.
Related posts:
- Lung cancer CT screening produces false positives and isn’t ready for prime time
- Should tobacco companies pay for smokers’ CT scans to screen for lung cancer?
- Motives behind CT screening
- "A CT scan in hand is far better then no CT scan or biopsy at all"
- Why health reformers should be worried about the breast cancer screening backlash
- Prostate cancer screening in men over 75
- PSA and prostate cancer screening
{ 3 comments }
Kevin,
One thing that is often overlooked is the psychological impact of screening.
This is rarely discussed in studies, but patients who may have a problem get extremely worried. Also there is stress associated with having a test and awaiting the results.
I blogged on one study that concluded that men that had a negative prostate biopsy had a worse quality of life conpared to men that did not have a prostate biopsy:
http://www.njurology.com/RoboticSurgeryBlog/2007/03/quality_of_life_after_a_negati.php
Excellent point! EBM is a wonderful roadmap for clinical work but often fails to include the real world that people face. That is the crux of all these discussions on screening over the past week.
Even when we talk about screening that has been shown to save lives, the discussion of potential harms is important.
While the magnitude of mortality reduction benefit (and this is desease-specific mortality, by the way, not all-cause mortality) seems large when one looks at population, the probability of an individual benefitting is often small. For come individuals, maybe even for majority, these small numbers may be enough to overlook potential harm of false positives and overdiagnosis. For others, 1/500 chance in 10 years (for example) of benefit, may just not be worth the risks.
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