CT scans for lung cancer screening may not save lives

Should smokers receive screening CT scans?

As it stands, there’s no evidence that screening patients with either chest x-rays or CT scans save lives, but a large, federally-funded study should yield some answers in the next year or so.

Recently, however, there’s data suggesting that screening chest CT scans for lung cancer gives a lot of false positives. Needless to say, these false positives are magnified with CT scans versus a conventional x-ray:

Among those who received CT scans, 21% had a false positive after one scan and 33% after two scans. For those who received chest X-rays, 9% had a false positive after one and 15% had a false positive after two. More than half of those with a positive finding had a follow-up scan or chest X-ray. About 7% in the CT scan group and 4% in the chest X-ray group had an unnecessary invasive medical procedure, typically bronchoscopy.

As David Leonhardt wrote in the New York Times, arguments like these are “soulless.” One anecdote of life-saving early detection wipes out rigorous data that suggests adverse complications from unnecessary testing.

If you don’t believe me, consider the firestorm that erupted after the USPSTF modified their breast cancer screening guidelines.

There will always be a subset of the population who believes that more testing means better medicine. It’s up to doctors and health reformers to convince patients otherwise, and warn them of the potential complications stemming from unnecessary tests.

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  • Marc Gorayeb, MD

    And now for the rest of the story…..
    “…screening CT was true-positive in 38 instances (2% of participants) and chest radiography was true-positive in 16 instances (1% of participants).” “The proportion of participants who had a moderately invasive procedure was 4% for false-positive CT and 3% for false-positive chest radiography. Rates of participants who had major surgical procedures for benign disease were similar (2%), although absolute numbers differed by a factor of 2 (8 CT recipients and 4 chest radiography recipients).”
    The authors did not report any complications related to the surgical procedures.
    This was a study of 3318 persons, 1610 of whom has a CT, and 1580 of whom had an Xray. Thus 54 true-positive cases were detected from a screening population of 3318. If I were one of those 54 persons, I would be rejoicing that I was selected for this study.
    I am not necessarily lobbying for using CT scans or chest Xrays for cancer screening, but the issue is not as ‘clean’ as this one-sided posting would suggest.

  • Diora

    “screening CT was true-positive in 38 instances (2% of participants) and chest radiography was true-positive in 16 instances (1% of participants).”

    How many of these true positives were overdiagnosis?

    In how many of these true positives early detection actually made a difference?

    The true positive numbers are not that meaningful without this additional info.

  • SarahW

    Doh! that link won’t get you beyond Medscape’s wall.
    Here is the link to the abstract of the research discussed in the the article:

    http://jnci.oxfordjournals.org/cgi/content/abstract/djq101

  • SarahW

    Diora – Did you see this? http://tiny.cc/2lhbr

    Sounds like a promising way to prevent DCIS overdiagnosis.

  • http://www.MDWhistleblower.blogspot.com Michael Kirsch, M.D.

    The last thing the public needs are more chest CAT scans. We already cannot cope with the zillions of innocent nodules being discovered by precise scans reported by nervous radiologists. These folks, after seeing a pulmonogist, will get serial scans for the next 2 years. Screening CAT scans will just take us farther in the wrong direction. There is not a shred of proof of benefit (beyond some stray anecdotes) and incontrovertible proof of harm and financial waste.