In more than 50 percent of the patients, the cancer will have spread to distant sites. Only 20 to 25 percent will be localized and can be surgically removed for a cure.

In a study that screened 1,520 individuals age 50 and over at high risk for lung cancer, low-dose computed tomography detected 23 cases alone while sputum cytology analysis detected two alone, according to an article in the second issue for February of the American Thoracic Society's peer-reviewed journal.

Research studies have suggested that screening with spiral computed tomography can detect lung cancers at a smaller size (less than 2 cm in diameter) and early stage (85 to 93 percent Stage I) as compared with chest radiography and clinical practice.

Writing in the current American Journal of Respiratory and Critical Care Medicine, Stephen J. Swenson, M.D., of the Mayo Clinic, Rochester, Minnesota, in association with 12 colleagues, said that, along with the cancers, 2,244 uncalcified lung nodules were identified in over 1,000 participants (66 percent), after two years of study.

"We estimate that 98 percent of these are falsely positive findings," he said.

The authors were concerned not only about the very high false positive rate for computed tomography screening, but also a high false negative rate. It seems that 26 percent of the participants had nodules that were missed during the baseline scan.

Twenty-two of the patients with identified cancers underwent curative surgical removal (resection), and seven benign nodules were also removed.

The idea behind this study was to test the hypothesis that screening with computed tomography in high risk patients would result in a downward shift to Stage IA or IB tumors at diagnosis.

The results show that 12 (57 percent) of the 21 non-small cell cancers detected by computed tomography were in a very early stage, IA, at diagnosis.

All participants were asymptomatic men and women 50 years of age or older who had smoked at least 20 pack years of cigarettes.

Only mentally competent men and women considered healthy enough to undergo pulmonary resection were admitted to the study. All participants agreed to undergo an initial prevalence computed tomography scan and three annual incidence scans.

During the study, 14 percent of the participants (21 persons) had incidental nonpulmonary findings of clinical significance. These problems included aortic aneurysm, renal cell carcinoma, bronchial carcinoid, breast cancer, gastric cancer and lymphoma.

Using the study group, the investigators are currently exploring the possibility of employing low-dose computed tomography to screen systematically for heart disease, stroke, emphysema, osteoporosis, and risk of cardiovascular disease, non-insulin dependent diabetes and hypertension.

According to the authors, low-dose computed tomography has the potential to be used as a comprehensive screening tool for many of the most common forms of death.


[Contact: Mary Lawson]

26-Feb-2002