Advances in spiral CT lung cancer screening

Although routine lung screening of high-risk asymptomatic patients is not currently recommended by the American Cancer Society (ACS) and the US Preventive Services Task Force, recent studies of spiral CT have generated interest in its potential screening capabilities.^1-3

Spiral CT, a technology introduced in the 1990s, can detect tumors of less than 1 cm—an improvement in sensitivity compared with that of chest radiography. Since spiral CT detects smaller primaries and more abnormalities than does chest radiography, strategies to minimize unproductive workups and iatrogenic complications will be essential to its integration as a screening tool.⁴ The technology continues to improve, with spiral CTs having evolved from the single detector scanners that were first studied 6 years ago, to the multidetector (64) scanners of today.⁴ These newer scanners are associated with greatly improved imaging resolution, which can facilitate more accurate quantitative assessment of tumor nodules in the lung.⁴

The Early Lung Cancer Action Project was among the first major studies to show the ability of spiral CT to detect noncalcified nodules in high-risk asymptomatic patients; nearly 90% of the nodules biopsied were diagnosed as malignant.⁵ A more recent study of low-dose spiral CT in heavy smokers revealed that spiral CT plus selective positron emission tomography shows great promise for the early detection of lung cancer, and that a watchful waiting program may be best for lesions of 5 mm or less to avoid unnecessary invasive procedures for lesions that could be benign.⁶

Based on these and numerous other encouraging study results, the National Cancer Institute developed the National Lung Screening Trial—the first randomized controlled trial comparing chest radiographs and spiral CT scans in asymptomatic high-risk patients, with lung cancer mortality as an end point. Nearly 50,000 persons aged 55 to 74 with a history of heavy or long-term smoking have been randomized to receive either 3 annual low-dose CTs or 3 annual chest radiographs. The trial, now closed to further enrollments, will continue data collection and analysis for 8 years. Study results are expected to determine the comparative value of early lung cancer detection with chest radiography and spiral CT for reducing deaths from lung cancer. Further, the study should provide insights into whether mortality benefits of spiral CT screening outweigh risks such as false-positive results (leading to anxiety and invasive procedures) and overdiagnosis (leading to unnecessary diagnosis of lung cancer requiring surgery).

Unfortunately, significant outcome information cannot be expected for approximately 5 more years. Until further research elucidates its value, the ACS recommends that patients considering lung cancer screening discuss what is known and not known about the potential benefits and harms associated with testing for early lung cancer detection.¹ Based on the existing evidence, current smokers should be informed that they are more likely to benefit from smoking cessation than screening.

1. Smith RA, Cokkinides V, Eyre HJ. American Cancer Society Guidelines for the Early Detection of Cancer, 2005. CA Cancer J Clin. 2005;55:31-44.

2. Humphrey LL, Teutsch S, Johnson M. Lung cancer screening with sputum cytological examination, chest radiography and computer tomography: An update for the US Preventive Services Task Force. Ann Intern Med. 2004;140:740-753.

3. National Cancer Institute. Lung Cancer: Screening. Available at: http://www.cancer.gov/cancertopics/pdq/screening/lung/healthprofessional/allpages/print Accessed July 27, 2005.

4. Mulshine JL. New developments in lung cancer screening. J Clin Oncol. 2005;23:3198-3202.

5. Henschke CI, McCauley DI, Yankelevitz DF, et al. Early Lung Cancer Action Project: overall design and findings from baseline screening. Lancet. 1999;354:99-105.

6. Pastorino U, Bellomi M, Landoni C, et al. Early lung-cancer detection with spiral CT and positron emission tomography in heavy smokers: 2-year results. Lancet. 2003;362:593-597.