Low-dose computed tomography reduces lung cancer mortality and all-cause mortality when used as a screening tool in asymptomatic adults at high risk for the disease, according to the results of a systematic review conducted for the U.S. Preventive Services Task Force.
In 2004, the USPSTF deemed the evidence insufficient for recommending for or against low-dose computed tomography (LDCT) for lung cancer screening in asymptomatic individuals, but the findings of the current review suggest screening has a definite benefit for most patients, Dr. Linda L. Humphrey, of Oregon Health and Science University and the Portland Veterans Affairs Medical Center, and her colleagues reported.
A draft recommendation based on the findings, published online in the July 30 issue of Annals of Internal Medicine (2013 July 29 [doi: 10.7326/0003-4819-159-6-201309170-00690]), is available on the USPSTF website for public comment.
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Lung cancer is the third most common cancer among men and women in the United States, but is the leading cause of cancer-related deaths, accounting for nearly 27%.
The researchers conducted a review of the literature published between 2000 and May 2013 and identified four trials that reported findings on the efficacy of LDCT screening in patients with smoking exposure for both intervention and control groups. Three small trials showed varying degrees of benefit with screening, but were underpowered; one large trial – the National Lung Screening Trial (NLST) – showed a significant 20% reduction in lung cancer mortality among those screened, as well as a 6.7% reduction in all-cause mortality.
The randomized multicenter NLST compared annual LDCT scans with annual single-view posterior-anterior chest radiographs for 3 years in more than 53,000 current or former smokers aged 55-74 years with at least a 30–pack-year history of smoking (N. Engl. J. Med. 2013;368:1980-91). One cancer death was prevented for every 320 patients who completed one screening, and one death from any cause was prevented for every 219 patients screened in that study; the trial was stopped early after 6.5 years of follow-up based on the findings.
In general, the benefits of LDCT for lung cancer screening in this population outweighed the risks, Dr. Humphrey and her colleagues noted.
Harms associated with LDCT, according to findings from 7 trials and 13 cohort studies that reported on such outcomes, included radiation exposure, overdiagnosis, and a high rate of false-positive findings that were resolved by further imaging in most cases. False negatives were reported in six studies, and the rates ranged from 0% to 20%, but none of the studies evaluated the harm of false reassurance, the investigators noted. The benefits of screening must be weighed against these potential harms.
Lung cancer is the third most common cancer among men and women in the United States, but is the leading cause of cancer-related deaths, accounting for nearly 27%. Furthermore, about 85% of U.S. lung cancer cases are attributable to smoking, and since about 20% of Americans currently smoke – and many more are former smokers who remain at increased risk because of their smoking history – "lung cancer will remain a major public health problem in this country for decades," the investigators wrote.
The studies included in this review were conducted in patients at high risk for lung cancer based on current or former smoking. However, patients at an increased risk for lung cancer, including older adults and those with a family history of lung cancer, chronic obstructive pulmonary disease, pulmonary fibrosis, and certain environmental and occupational exposures, may also benefit from LDCT screening.
"Future research to identify methods for focusing LDCT screening on persons at highest risk for disease, to improve discrimination between benign and malignant pulmonary nodules, and to find early indicators of aggressive disease is warranted," the investigators noted. "If LDCT screening becomes routine, the risk for harms should be measured and methods to limit them should be identified."
The review was funded by grants from the Agency for Healthcare Research and Quality and the Portland Veterans Affairs Medical Center. Dr. Humphrey is employed by the Department of Veterans Affairs, and she and her coauthors disclosed ties with UpToDate, the USPSTF, AHRQ, the Department of Veterans Affairs, the American Lung Association, the Chest/LUNGevity Foundation, the National Lung Cancer Partnership, and/or the American College of Chest Physicians.