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Consequences of screening for lung cancer (NELSON)

Clinical Question:
What are the consequences of a screening program for lung cancer?

Bottom Line:
Lung cancer screening with high-resolution computed tomography (CT) has a 36% positive predictive value and 99.7% negative predictive value during the first round of screening, but results in many biopsies and significant radiation exposure. Remember, for every 1000 to 2000 chest CT scans in an adult, we cause 1 solid tumor. Since this group had a total 17,000 scans over 2 years, the screening program caused an additional 12 to 18 solid tumors (Arch Intern Med 2009;169:2078). Also, it is not clear how many of these early-stage cancers would have progressed to become clinical cancers or harm the patient; the answer to that will have to await the comparison with the control patients who were not screened. (LOE = 2b)

Reference:
van Klaveren RJ, Oudkerk M, Prokop M, et al. Management of lung nodules detected by volume CT scanning. N Engl J Med 2009;361(23):2221-2229.  [PMID:19955524]

Study Design:
Cohort (prospective)

Allocation:
Uncertain

Setting:
Population-based

Synopsis:
This study reports early data from a large, 10-year randomized trial of CT as a screening test for lung cancer. Patients underwent a baseline CT examination using a 16-detector unit, followed by repeated examinations 1 year and 3 years later. The mean age of participants was 59 years, with 42 pack-years of smoking; 84% were male. Nodules are very common, and the researchers used the following protocol: solid nodules more than 500 cubic mm (9.8 mm diameter) were positive; solid nodules 50 mm to 500 mm (4.6 mm to 9.8 mm diameter) and nonsolid nodules greater than 8 mm diameter were indeterminate; and all other nodules were negative. Patients with a positive nodule were referred to a thoracic surgeon for further evaluation and those with an indeterminate nodule were scanned 3 months later; if the nodule had a doubling time of less than 400 days, they were also considered positive and referred. In the baseline scan, half of the 7557 participants had a noncalcified nodule, of which 19.2% were indeterminate and 1.6% were positive. Of the 1536 follow-up scans obtained 3 months later, 77 were positive, for a total of 196 positive scans and 177 referrals from the first round of screening. Of those 177 persons, most of whom underwent biopsy, 70 had lung cancer, of which 64% were stage I, for a lung cancer detection rate of 0.9% (positive predictive value = 36%). Of the 7361 patients with negative baseline CT scans, 20 had a lung cancer detected during the next 2 years (negative predictive value = 99.7%). Of the 107 with a positive baseline screening result who were not diagnosed with cancer, 10 had lung cancer detected during later rounds of screening. In the second round of screening 1 year later, which followed a similar protocol, 480 of 7289 patients tested indeterminate and required a 3-month repeat scan. Ultimately, a total of 128 of 7289 tested positive in the second round of scanning (1.8%), of whom 54 had lung cancer (0.7%).

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