The US Preventive Services Task Force (USPSTF), that most august body, has just put out a
draft recommendation for lung cancer, making it available for public comment thru Aug 26th. This
Grade B recommendation to annually screen smokers with low dose CT scan was based upon a
systematic review of currently available evidence published online yesterday in the Annals of Internal Medicine.
So what's this mean for you & me? Well, the evidence was given a B grade. In other words, USPSTF believes that there is high certainty that net benefit is moderate or that there is moderate certainty that net benefit is moderate to substantial. Did you catch that? It's not an A grade in which USPSTF would believe that there is high certainty that net benefit is substantial.
High certainty means that the available evidence is consistent and derived from well-designed & well-conducted studies, and as such are unlikely to be affected by future data. OK, that's fine but if you read the systematic review itself, the
USPSTF could only find 4 trials, of which
only one was large & of good quality showing significant benefit in lung cancer & all-cause mortality. The
other 3 were small (underpowered) & did not demonstrate any benefit (insufficient duration to evaluate effectiveness). So how is the evidence consistent? And how is it that underpowered studies of insufficient duration were judged well-designed & well-conducted?
Before you jump to conclusions and rush out for your own LDCT scan, read the evidence review yourself. And ask the USPSTF (by commenting on their website) if the evidence is really that good & strong enough to support these draft recommendations?
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