Study calls for routine CT scans for smokers
The use of advanced CT imaging to detect lung tumors in their still-treatable early stages greatly increases survival rates, and smokers should be routinely screened just as women are for breast cancer, according to a report today in the New England Journal of Medicine.
Imaging yielded an estimated 10-year survival rate of more than 90%, researchers said. Currently, about 5% of the 174,000 lung cancer patients diagnosed each year survive for 10 years.
The study of more than 30,000 patients shows the scans to be as cost-effective and beneficial as mammography is for breast cancer, the researchers said.
“This is compelling evidence that you can use CT screening to find lung cancer ... and when you find it early and take it out early, you can cure a high percentage of patients,” said Dr. Claudia I. Henschke of Cornell University’s Weill Medical College in New York City, who led the study.
CT scans produce a sharp, three-dimensional image of the chest that allows physicians to detect much smaller objects than can be seen on a conventional chest X-ray.
Laurie Fenton, president of the Lung Cancer Alliance, joined Henschke in calling for routine screening. The results “flip lung cancer survival statistics on their head,” she said.
Some cancer experts, however, said that the study does not prove that screening reduces deaths from the disease and that it is too soon to recommend widespread use.
It is possible that the screening simply revealed many slow-growing or benign tumors that would not have caused problems if they had not been identified, said Dr. David Johnson of Vanderbilt University, past president of the American Society of Clinical Oncology.
Researchers can only identify a definitive benefit if there is a control group that does not undergo CT screening, similar to the placebo group in a drug trial.
“The real gold standard for determining whether screening is useful is whether it impacts on mortality,” Johnson said. Although the new results are promising, “these data don’t answer that question.”
National cancer organizations do not recommend screening for lung cancer, and this study seems unlikely to change that stance.
“Health policy isn’t made on the basis of one study,” said Robert A. Smith, the American Cancer Society’s director of screening.
He and other experts agreed that no change in policy is likely until the end of the decade, when results will be available from large trials conducted by the National Institutes of Health and the Mayo Clinic in Rochester, Minn., comparing CT screening to conventional chest X-rays.
The current consensus against screening stems from studies in the 1970s that showed screening with conventional chest X-rays produced no increase in survival because they failed to show many tumors.
But modern technology has changed the equation, Henschke said. Her team reported in a smaller study in 1999 that CT scanning could increase the detection of small tumors and improve outcomes. That report was the impetus for the studies now underway.
The technology has improved more since then, she said, with the widespread adoption of so-called spiral CT scanners, which increase sensitivity by allowing a scan of the chest to be completed in only 20 seconds -- the duration of one held breath. The scans, which use a very low dose of radiation, cost about $200.
Critics have charged, however, that the CT scans are too sensitive, identifying many nodules that are not cancerous and thereby necessitating biopsies, which themselves carry risks to the patient.
In the new study, researchers at 38 institutions around the world screened 31,567 apparently healthy people who were at increased risk of lung cancer because they were lifelong smokers, had high exposure to secondhand smoke or had occupational exposure to lung carcinogens. They were screened a second time a year later.
The team found 4,186 nodules in the initial screening and 1,460 more in the one-year screening. The small nodules were monitored for three months with additional scans. If the nodules were growing, the patients received a biopsy to determine whether the nodules were cancerous.
A biopsy was performed in 535 patients, and 492 were found to have lung cancer or metastases from cancers at other sites. Most had surgery or chemotherapy.
The researchers took their results at the end of three years and estimated 10-year survival. Considering all the tumors identified, the estimated 10-year survival rate was 80%. If the tumor was detected at an early stage, the 10-year survival was 88%, and if the patient underwent surgery within a month of diagnosis, the survival was 92%.
All eight patients who refused treatment died within a year.
“If this is the pattern of survival for screen-detected lung cancers, that is very good news,” the cancer society’s Smith said. They “show real promise for reducing this country’s top cause of cancer death.”
In the absence of national guidelines, the one thing on which experts on both sides agree is that patients in high-risk groups should talk to their physician about the advisability of screening.
And if screening is advisable, the physician should follow the protocol used in the study to minimize false positives and unnecessary biopsies.
The study was sponsored by several public and private agencies, but no funding was received from instrument manufacturers. The researchers reported no conflicts of interest.
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