The National Cancer Institute (NCI) has recruited 3,000 current and former smokers for the Lung Screening Study, a year-long, $3 million study of spiral computed tomography (CT) scans, promising but unproven technology for lung cancer screening. While the study will not determine if the scans save lives--the gold standard for any cancer screening test--it will gauge the feasibility of a larger, longer study designed for that goal.
During September and October, six screening centers across the country recruited 500 people and randomly assigned them to receive either a spiral CT scan or a chest X-ray. During the active phase of the study, researchers will determine the willingness of smokers and former smokers to participate in a randomized study. In addition, they will compare the lung cancer detection rate of each test; measure how much and what kind of medical follow-up is needed for positive or ambiguous results; and track how frequently participants receive spiral CT scans outside of the study.
All of this knowledge is crucial for the design of larger, more definitive studies, said John Gohagan, Ph.D., the NCI investigator heading the study. "In a relatively quick time frame we will learn if smokers are willing to be randomized to receive something other than a spiral CT scan. We will also learn about the medical follow-up of people who have the scans, how extensive and expensive it tends to be," he said. Gohagan is chief of the Early Detection Research Group in NCI's Division of Cancer Prevention.
Board certified radiologists will review each CT scan and X-ray; results will be mailed to participants and their physicians within three weeks of the screen. For those with positive chest X-rays, the screening center will recommend standard follow-up care. Because no such standard of care exists for spiral CT scans, participants with suspicious scans will be referred to their primary care physician and advised to consult a specialist for follow-up.
Evidence from early studies suggests that spiral CT scans detect small lung cancers, often at the edges of the lungs. However, whether finding these tumors actually saves lives remains unknown. The only way to detect a survival advantage is with a large study where people receiving the scans are tracked alongside a control group that does not get them; such research would be expensive, requiring tens of thousands of participants and five or more years.Thorough review of results from the Lung Screening Study will help researchers decide whether such a study is feasible.
Some in the medical community question whether smokers will participate in a clinical trial in which they might be randomized to receive a screening exam other than spiral CT. Screening spiral CT scans are available outside of clinical trials, though they cost $300 to $1,000 and health plans generally do not cover the charges.About half of the hospitals in the United States own spiral CT machines, each costing upwards of $1 million.Some of these hospitals have begun aggressively advertising the scans for the early detection of lung cancer, despite the lack of evidence that the scans reduce a person's likelihood of dying from lung cancer.
Furthermore, no estimates exist on the cost--in terms of dollar amounts or risk to the patient--of the follow-up care that screening with CT scans may require.Scarring from smoking and other noncancerous changes inside the lungs tend to mimic tumors on the scans, challenging the radiologists who read them.Interpretations of the scans often vary, leading to disagreement about follow-up care.Radiologists and clinicians often recommend additional scans, biopsies, chest surgery, or other diagnostic tests.
In fact, a recent report (a 20-year follow-up of the Mayo Lung Project, which used chest X-rays to screen for lung cancer, published in the Aug. 16, 2000, Journal of the National Cancer Institute) suggests that screening for lung cancer may detect tumors that never become life threatening.Called over-diagnosis, this phenomenon may put screening recipients at risk from unnecessary biopsies or surgery. Possible complications from these procedures include chronic pain or nerve damage. By following participants after spiral CT scanning, the Lung Screening Study will help researchers understand risks associated with the scans.
For quick results, the study builds on the scientific infrastructure of the 150,000 participant Prostate, Lung, Colon, and Ovarian Cancer Screening Trial (PLCO), launched by NCI in 1992. As all are involved in PLCO, the six Lung Screening Study centers offer extensive experience recruiting and tracking participants in cancer screening studies.
The six participating centers are Georgetown University Medical Center/Lombardi Cancer Research Center (Washington, D.C.); Henry Ford Health System (Detroit); the University of Minnesota School of Public Health/Virginia L. Piper Cancer Institute (Minneapolis); Washington University School of Medicine (St. Louis); Marshfield Medical Research and Education Foundation (Marshfield, Wis.); and the University of Alabama at Birmingham. In addition, Westat, Rockville, Md., will serve as the data coordinating center.
Lung cancer is the leading cause of cancer-related death in the United States, expected to claim 156,900 lives this year. It will be diagnosed in an estimated 164,100 people in 2000, usually only after symptoms appear.To date, no screening technology has been proven effective in reducing the number of deaths from lung cancer. Approximately 85 percent of lung cancers are caused by smoking.
Participants in the study must be between the ages of 55 and 74. Participants also must have a history of long-term or heavy smoking; former smokers must have quit within the last 10 years. People who have a history of lung cancer or who are participating in PLCO are ineligible.
Call the NCI's Cancer Information Service at 1-800-4-CANCER for more information about the Lung Screening Study or for information about quitting smoking or lung cancer.
Spiral CT uses X-rays to scan the entire chest in about 15 seconds, during a single breath-hold. Throughout the procedure, the patient lies still on a table.The table and patient pass through the CT machine, which is shaped like a donut with a large hole. The machine rotates around the patient and a computer creates images from the scan, assembling them into a 3-D model of the lungs. The amount of radiation absorbed during a spiral CT scan is comparable to that absorbed during a mammography.