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Screening chest x-ray detects early-stage lung cancers at high rates, study results show

December 21, 2005

Almost half of lung cancers detected by a chest x-ray were early-stage cancers, according to baseline results of a large, randomized clinical trial that is testing the efficacy of a chest x-ray as a screening test for lung cancer. The study results are published in the December 21 issue of the Journal of the National Cancer Institute.

Lung cancer causes one million deaths worldwide every year. When patients begin to experience symptoms of lung cancer, the cancers are often advanced and treatment is rarely successful; 90% of newly diagnosed lung cancer patients die within 2 years of diagnosis.

In 1992, The National Cancer Institute launched the still-ongoing Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial to evaluate screening tests for each of the four cancers. The PLCO Cancer Screening Trial is the largest trial ever conducted in the United States. The 155,000 men and women enrolled in the study were asked about past and present smoking habits, medical history of themselves and their families, and personal characteristics. For the lung cancer portion of the trial, participants were randomly assigned to a control group or to a screening group that received a single-view, posterior-anterior chest x-ray.

According to the baseline results of the 77,465 patients in the screening group, reported by Martin M. Oken, M.D., of the Hubert H. Humphrey Cancer Center in Robbinsdale, Minn., and colleagues from the PLCO Project Team, 5991 (8.9%) participants had a test result that was suspicious for cancer, and after further follow-up and medical tests, 126 participants were diagnosed with lung cancer. Forty-four percent of the cancers found were diagnosed as stage I cancers. Chest x-ray detected 6.3 lung cancers per 1000 current smokers, 4.9 lung cancers per 1000 former smokers who had smoked in the past 15 years, 1.1 lung cancers per 1000 former smokers who had not smoked within the past 15 years, and 0.4 lung cancers per 1000 never-smokers. Chest x-ray found cancer at a higher rate in men than in women.

"The data suggest a high rate of early detection and possibly important differences between screening for lung cancer in women and in men," write the authors. "The answer to the important question of reduction in lung cancer mortality must await analysis of the two study arms as these data mature."

Journal of the National Cancer Institute