By Steven Reinberg
SUNDAY, May 20 (HealthDay News) -- Using low-dose CT scans to screen for lung cancer might save the lives of patients at the greatest risk for the disease, a new analysis suggests.
However, the risks of screening for others aren't clear, the researchers added.
"We have insight into risks, but they are hard to weigh and estimate," said lead researcher Dr. Peter Bach, from Memorial Sloan-Kettering Cancer Center in New York City.
"It's clear that when you screen you find cancers that otherwise wouldn't appear, and that leads to overtreatment," he said. "It is clear that CTs find lots of things that aren't cancer. About one in five people have something found that will require some sort of follow-up."
There is also an excess radiation risk. In one trial, screening prevented about three deaths per 1,000 people screened, while one in 2,500 might develop cancer from the CT scan, Bach said.
However, in the right population it could theoretically prevent thousands of deaths a year, he explained.
Namely, that population is the heaviest smokers, those who smoke for 30 pack-years or more. A pack-year is the number of cigarettes smoked over time. This means at least a pack a day for 30 years or two packs a day for 15 years.
"For these patients, we recommend that doctors might suggest screening and discuss the risks and benefits," Bach said. "But, no one should be telling people that they must have this test or advertise that it's a lifesaving procedure that will prevent you from dying from lung cancer."
In the end, "there is no substitution for smoking cessation in terms of health benefits," Bach noted.
The report was published online May 20 in the Journal of the American Medical Association.
For the study, Bach's team reviewed 21 studies about the benefits and risks of low-dose CT screening for lung cancer.
One of the studies, the National Lung Screening Trial, included more than 53,000 people and found that screening reduced deaths from lung cancer by 20 percent, the researchers said.
The results of that trial were published last June in the New England Journal of Medicine.
However, the other, smaller trials found no benefit from screening, Bach's team noted.
The study authors found that, overall, 20 percent of patients had a scan that needed follow-up, but only 1 percent had lung cancer.
The studies were done in teaching hospitals with experienced radiologists and cancer doctors, Bach noted.
This report is the basis of the screening recommendations adopted by the American College of Chest Physicians and the American Society of Clinical Oncology.
The recommendations state that heavy smokers aged 55 to 74, and those who have quit in the past 15 years, should be offered screening.
But screening should only be done at hospitals that do a lot of this kind of screening. These are usually large or teaching hospitals, because the value of this screening at community hospitals is not known, Bach added.
Dr. Norman Edelman, chief medical officer at the American Lung Association, called the new study a "thoughtful analysis of an important topic."
The American Lung Association conducted a similar review and came to similar conclusions, he said.
The data suggest that screening heavy smokers is likely to reduce death from lung cancer by about 20 percent and all-cause mortality by about 10 percent, he said.
"Given the large cohort to which it pertains, this would be a significant public health achievement," Edelman stated.
However, there remain many unsettled issues, he said.
"One major issue is whether the same results would be observed in the community as opposed to the controlled academic settings in which the study was done," Edelman said. "Accordingly, the American Lung Association report emphasizes the need for screening to be done in centers which can provide low-dose CT screening and a comprehensive multi-specialty environment, so that finding of suspect nodules can be followed up with appropriate [care] rather than undue risk."