Screening smokers several times a year with chest X-rays does not reduce their odds of dying from lung cancer and may lead some people to undergo unnecessary treatment for lung tumors that would never have been fatal, new research suggests. The findings call into question the wisdom of using a relatively new, more powerful lung screening technique to detect lung cancer.

• Researchers at the National Cancer Institute (NCI) assigned more than 9,000 male smokers to undergo a chest X-ray and sputum cytology (examining phlegm under the microscope to detect cancer cells) three times a year for 6 years or were advised to have the same tests only once a year.

• The first participants were enrolled in 1971, and by 1983, men who underwent frequent screening were no less likely to die from lung cancer than other men.

• Even after an average of more than 20 years of follow-up, the results were still the same.

"We found no reduction in lung cancer mortality," said one of the researchers in comments to Reuters Health. As a matter of fact, in the intense-screening group, 337 men died from lung cancer, compared with only 303 of the men who were advised to be screened just once a year.

• According to the authors, the chest x-rays seem to detect some very small or slow-growing lung tumors that may never threaten lives.

• Additionally, procedures and surgery to evaluate or remove these detected growths can be risky.

Dr. Pamela M. Marcus, of the NCI said that the idea that some lung tumors may be present for years without ever causing symptoms is "pretty heretical," towards the current beliefs. The results of the study should also give doctors second thoughts about using a powerful new imaging test, known as spiral computed tomography (CT), to screen for lung cancer. Although it may be capable of detecting lung lesions in their early stages, there is no proof that the test can reduce lung-cancer deaths.

"It hasn't been shown that spiral CT reduces lung cancer mortality," Dr. Marcus said. "We shouldn't be jumping on the spiral CT bandwagon yet."

Journal of the National Cancer Institute August 16, 2000; 92.