The first report of an international study looking at computed tomography (CT) to screen current or former smokers for lung cancer found that screening did not reduce deaths from lung cancer. Although CT screening found nearly three times as many lung cancers as predicted, the researchers found that early detection and treatment did not lead to a corresponding decrease in advanced lung cancers or a reduction in deaths from lung cancer. The multi-center study, led by researchers at Memorial Sloan-Kettering Cancer Center, found no advantage to using CT screening on current or former smokers -- the population at highest risk for developing lung cancer.
"Ours is the first study to ask whether detecting very small growths in the lung by CT is the same as intercepting cancers before they spread and become incurable. We found an answer and it was, 'NO'," said Peter B. Bach, M.D., M.A.P.P., a lung physician and epidemiologist at Memorial Sloan-Kettering and the study's first author. "Early detection and additional treatment did not save lives but did subject patients to invasive and possibly unnecessary treatments."
Beginning in 1998, 3246 asymptomatic men and women with a median age of 60 who had smoked or still smoked for an average of 39 years were screened for lung cancer with state-of-the-art multi-detector CT at either the Mayo Clinic in Minnesota, the H. Lee Moffitt Cancer Center & Research Institute in Florida, or the Instituto Tumori in Italy. Each study provided an initial CT scan and then at least three subsequent annual exams. The researchers followed the volunteers to see how many had cancers detected by screening and how many had surgery to remove them. They then used government death records to follow the study participants for five years to see if they died of lung cancer. The researchers compared what they saw to what statistical models predicted would happen without screening. The models were developed for this purpose by Dr. Bach and Colin B. Begg, Ph.D., Chairman of the Department of Epidemiology and Biostatistics at Memorial Sloan-Kettering, and have been shown to be accurate in study populations like the ones analyzed.
Over the course of the studies, screening found more than three times as many lung cancers as the number that would have been diagnosed without screening, and there were ten times as many surgeries performed for lung cancer compared to what was expected. This meant that as a direct result of the test, an additional 99 people were diagnosed with lung cancer and an additional 98 had lung surgery. However, the early detection and treatment did not change the death rate. There were 38 deaths due to lung cancer, and 39 would have occurred without screening.
"The purpose of large-scale screening is to save lives, but after five years of follow-up, our data provides no evidence that CT screening prevented deaths from lung cancer," said Dr. Begg, the paper's senior author. "Our findings are consistent with the results of earlier studies of lung cancer screening with chest x-rays, which showed no benefit to this type of screening for current and former smokers."
CT screening is not without risk. The radiation can become significant when the scans are repeated every year. Because the test is not very specific, it is known to have false positive results, which can lead to additional CT scans at full radiation doses and invasive procedures like lung biopsies. This study also suggests CT screening can lead to additional major surgeries to remove very small growths that look like lung cancer but do not pose a meaningful threat to the patient's health.
"With lung cancer the number one cause of cancer deaths in the United States, the medical profession continues to seek an effective and safe approach to prevent deaths from this disease. According to our study, CT screening may not be it," said Dr. Bach.