Key Point

Lung cancer screening via CT does not appear to detect cancer before progression to the advanced stage, or to reduce mortality.

NEW YORK CITY—About a quarter of cancer deaths in the United States are attributable to lung cancer, yet which screening methods, if any, are effective to reduce mortality and to identify cases in the early stages of the disease is still a matter of debate. Preliminary study results suggest that low-dose CT screening is not the answer, reported Peter B. Bach, MD, MAPP, of Memorial Sloan-Kettering Cancer Center in New York City, and colleagues in the March 7 JAMA.

Their findings corroborate previous research, which found that radiologic imaging may increase detection of small, resectable cancers and thus increase the rate of lung surgery. Yet, “there appears to be neither a meaningful reduction in the number of advanced cancers being diagnosed nor a reduction in the number of individuals who die of lung cancer,” the study authors contended. “These findings … should raise doubts about the premise underpinning CT screening for lung cancer, and also raise concerns about its potential harms if pursued on a wide scale.”

ESTIMATE MODELS BASED ON INDIVIDUAL RISK

The researchers analyzed data from 3,246 persons enrolled in one of three single-arm lung cancer–screening studies conducted in Italy (where lung cancer accounts for 20% of cancer deaths), Minnesota, and Florida. In all studies, participants had a history of smoking and no history or symptoms suggestive of lung cancer.

The investigators evaluated the number of persons with a first diagnosis of non–small cell or small cell lung cancer, the number of first surgical resections of lung cancer, and the number of persons who died from lung cancer. A total of 89% of participants were followed for two years, 71% for as long as three years, and only 33% for more than four years; however, adjustment was made to account for patients lost to follow-up. The frequency of lung cancer events was compared with estimate models of individual risk of lung cancer incidence and mortality.

A combined total of 144 lung cancer cases were identified in the three study cohorts; this total was more than three times the number of expected cases (44.5). Similarly, the researchers found that there were 10 times more lung cancer surgeries than expected (109 vs 10.9).

As has been found in previous studies of CT screening, most lung cancers (67%) were stage I or II, yet “early detection via CT screening did not appear to reduce the risk of advanced lung cancer diagnoses,” the authors said. Specifically, the number of advanced (stage III or IV) lung cancer cases (42) exceeded the number predicted (33.4). There were 38 deaths due to lung cancer after the first year of screening versus 38.8 predicted by the model, the investigators noted.

A longer follow-up period and a larger sample size may have allowed for the detection of a screening benefit, the authors acknowledged. Clinicians should await the findings from ongoing and upcoming studies, such as the National Lung Screening Trial, before wholeheartedly embracing CT as a viable lung cancer–screening tool, they concluded.

CONFLICTING RESEARCH

In an accompanying editorial, William C. Black, MD, and John A. Baron, MD, noted that study results published last year in the New England Journal of Medicine4 indicated that in 31,567 asymptomatic persons at risk for lung cancer, annual CT lung cancer screening detected 484 cancers; of these, 85% were stage I and, ostensibly, more likely to be curable. In addition, the survival rate was 92%. Yet the seemingly contrasting findings may, in part, be due to differences in methodology, study population, or screening protocols.

In any event, randomized controlled trials yield the most accurate data, noted Drs. Black and Baron. “Although expensive and time-consuming, rigorous trials of cancer screening are far more cost-effective than what might be the alternative—widespread adoption of costly screening interventions that cause more harm than good,” the editorialists contended.           

—Adriene Marshall

Suggested Reading
Bach PB, Jett JR, Pastorino U, et al. Computed tomography screening and lung cancer outcomes. JAMA. 2007;297:953-961.
National Cancer Institute. National Lung Screening Trial. Available at: www.cancer.gov/nlst. Accessed March 9, 2007.
Black WC, Baron JA. CT screening for lung cancer: spiraling into confusion? JAMA. 2007;297:995-997.
Henschke CI, Yankelevitz DF, Libby DM, et al; International Early Lung Cancer Action Program Investigators. Survival of patients with stage I lung cancer detected on CT screening. N Engl J Med. 2006;355:1763-1771.

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