Ma et al. present the annual number of deaths
delayed or prevented by low-dose computed tomography lung cancer screening.
Even if the overall estimate of 12,000 may be inaccurate for a number of
reasons, the overall magnitude is large enough to serve as a slap in the face.
The editorial by Dr. Kessler very nicely discusses many relevant points
regarding lung screening. For emphasis, I reiterate some of Dr. Ma’s and Dr.
Kessler’s points.
Dr. Ma and his colleagues based their primary results
on the NLST-observed lung cancer mortality reduction of 20% and application of
NLST entry criteria for selection of screenees. This mortality reduction was
observed in the ideal randomized screening trial setting.
In everyday practice, screening success may fall far
well short of the trial-observed mortality. Widespread public health screening
initiatives work best if implemented as systematic programs rather than
“opportunistic” screening, as is most likely to occur in the United States.
Thus, achievement of 20% lung cancer mortality reduction may be difficult to
obtain.
On the other hand, long-term annual screening may lead
to greater effectiveness of screening than was observed in the NLST with only
three screens. Furthermore, if one selected 8.6 million people for screening
based on elevated lung cancer risk prediction model probabilities, an
additional 2,750 deaths may be averted, as an estimated 41% fewer lung cancer
would be missed, compared with application of the NLST criteria (N. Engl. J. Med.
2013;368:728-36).
Whether to and how to optimally implement lung cancer
screening is still muddled. Within the next year, we anticipate several
important additions to lung cancer screening knowledge: CISNET models will be
published that will shed light on the impact of varying screening parameters;
the U.S. Preventive Services Task Force is expected to provide guidance with
regard to lung screening; and pulmonary nodule malignancy prediction models
based on prospective population-based data will help guide clinicians with
respect to true- vs. false-positive lung screens.
Dr. Tammemägi is a professor of
epidemiology at Brock University in St. Catharines, Ont.
