Tuesday, October 29, 2013

Why don't physicians discuss cancer screening harms?

- Kenny Lin, MD, MPH

Last month, I attended a conference that included an exercise where attendees were asked how many patients they thought it was acceptable to diagnose and treat needlessly (or "overtreat") in order to prevent one death from cancer. We stood at various points along a wall that represented different thresholds: at one end, 100 persons overtreated for every 1 life saved; at the other, 1 person overtreated for every 1 life saved. Not surprisingly, attendees held a wide range of opinions (I stood somewhere in the middle), but the exercise illustrated the tradeoff inherent in effective screening tests for breast, colorectal, and cervical cancer: for every person who benefits from screening, others will be harmed. This fact has led many physicians to advocate that shared decision-making be used more widely to integrate patients' preferences and values with the decision to accept or decline a screening test.

How often do physicians take the time to explain the harms of cancer screening to their patients? A research letter published in JAMA Internal Medicine explored this question in an online survey of 317 U.S. adults between 50 and 69 years of age. 83 percent of participants had attended at least 1 routine cancer screening; 27 percent had undergone 3 or more. However, less than 10 percent of participants had ever been informed by their physicians of the risk that the screening test(s) could lead to overdiagnosis and overtreatment. The few physicians who did attempt to quantify this risk generally provided information that was inconsistent with the medical literature.

If the results of this survey are representative of the practices of U.S. family physicians, then more than 90 percent of us aren't telling patients that there are downsides to undergoing routine mammograms, colonoscopies, and Pap smears. Why not? Is it because we aren't familiar enough with the data to accurately describe these harms? Or is it because we fear that patients who receive information about cancer screening harms will choose to decline these tests?

1 comment:

  1. Thank you Kenny for your reflections. I'd add to them by the thought that while physicians are diverse in their belief as to how many overtreatments are "acceptable" in order to prevent one death from cancer - it really DOESN'T matter what physicians think the real number is. This is because the decision regarding potential to benefit vs potential for causing harm by performance of a screening test on an asymptomatic subject belongs with the informed patient - not with the physician. For some patients - screening may be worth it for a 1 in 1,000 chance to have their life saved by a screening test - whereas in others, screening is clearly "not worth it" unless the cance of saving their life is far greater. It all depends - and physicians really have no idea what "the number" is for any given patient.

    Then again - there is a LOT more to the equation than stated in the above paragraph. It is one thing to show an increase over time in average survival after diagnosis of a particuar kind of cancer - and quite another to PROVE that it was early discovery of the cancer with resultant treatment per se that truly prevented the patient from dying - vs earlier recognition of a cancer that never would have caused the patient harm. The latter increases survival statistically - but in reality simply converts a person to a patient by finding a cancer that never would have caused a problem (and which the person would have been better off not knowing about).

    There is also additional potential for harm from screening by finding other conditions that then lead to additional testing, worry, and potential for harm with minimal chance to improve lifespan or quality of life vs occasional pick-up of some other condition that would have been life-threatening had it gone unchecked. It becomes mind-boggling to "sum up" pros and cons of all of these factors into some meaningful net total.

    Finally - financial interests probably have a large role. It takes TIME to educate patients. It is far easier to "do" testing. Potential for financial conflicts are many and extend beyond the scope of my brief comment. Hopefully - awareness will continue to increase that screening asymptomatic individuals is not without potential for harm. There IS potential for benefit with screening - and for the individual whose colon cancer is detected at early enough stage to be cured by resection - n = 1, and the intervention is life-saving. But there are 2 sides to the equation - and the role of the physician includes full explanation of potential downside.

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