Study: CT scans reduce lung cancer deaths by 20% compared with X-rays
Thursday, November 4, 2010; 10:52 PM
Screening smokers and ex-smokers with high-tech CT scans has been shown for the first time to significantly cut deaths from lung cancer, the leading cancer killer, federal health officials said Thursday.
A long-awaited study of more than 53,000 middle-aged and elderly people who once smoked heavily or currently smoke heavily found 20 percent fewer deaths among those who underwent annual screening with a procedure known as low-dose helical computed tomography (CT), compared with those who had standard chest X-rays.
The findings were so striking that the National Cancer Institute, which sponsored the study, halted the National Lung Screening Trial early so that the public and the study participants could be alerted .
"This finding has important implications for public health with the potential to save many lives among those at greatest risk for lung cancer," said NCI Director Harold Varmus. "This finding will be an important factor in subsequent efforts to protect the tens of millions of former and current smokers in this country against the lethality of lung cancer."
Lung cancer strikes more than 196,000 Americans a year and kills more than 159,000 - more than breast, colorectal, pancreatic and prostate cancers combined. Significant advances have been made in reducing deaths from other cancers, but lung cancer remains stubbornly resistent, and most patients die. There are an estimated 91.5 million current and former smokers in the United States, all of them at increased risk of lung cancer.
Benefits and risks
A CT scan creates a three-dimensional image of the lungs, instead of the two-dimensional perspective captured by a chest X-ray. A scan is more likely to spot a tumor while it is still small and relatively susceptible to removal by surgery, boosting the chances of the patient's survival.
The findings were hailed by the American Cancer Society, the American Lung Association and others.
"With this positive trial result we have the opportunity to realize the greatest single reduction of cancer mortality in the history of the war on cancer," James L. Mulshine, a research official at Rush University Medical Center in Chicago, said in a statement issued by the Lung Cancer Alliance.
Even though CT scans can be performed by most hospitals, experts stressed that it is too soon to issue specific recommendations about the use of CT screening for lung cancer. More analysis is needed to identify who might benefit - perhaps those people who smoked less heavily - and how often patients should be screened, they said.
Some expressed concern that the findings might lead to an increase in the number of people undergoing unnecessary screening. The scans found abnormalities in about 25 percent of those screened, but most turned out to be false alarms.
"As with any study of screening, there are also potential harms to be considered, such as potential overdiagnosis and needless surgeries," said Otis W. Brawley, the American Cancer Society's chief medical officer. "We have learned from the long-term analysis of other screening tests, such as mammography, that it is important to consider both benefit and harms associated with the test."
Health experts increasingly have challenged the value of screening for a variety of health problems. In recent years, they have asked whether mammography for breast cancer, PSA testing for prostate cancer and Pap smears for cervical cancer were being overused, subjecting patients to needless tests and treatment.
"Will the public health community be able to manage the immediate consequences of this result, and ensure that there is a carefully planned rollout of screening to those individuals who will likely benefit, and with screening offered in places where follow-up care is available?" Peter Bach, a doctor and researcher at Memorial Sloan-Kettering Cancer Center in New York, wrote in an e-mail. "Or will we see an avalanche of entrepreneurial radiologists taking out full-page ads and billboards tomorrow overstating the magnitude of the benefit, and without any plan in place for how to handle whatever is found or how to select the right patients for screening?"
Previous studies produced mixed results on the usefulness of CT screening as a way to catch lung cancer in its earliest stages, when it is likely to be more treatable. It remained unclear whether the benefits of the scans outweighed the radiation risks and the dangers and anxiety related to unnecessary biopsies and other treatment caused by false alarms.
Emphasis on smoking
Experts stressed that smoking is the leading cause of lung cancer and that the best way to fight the disease is to never smoke or to stop smoking.
"These findings should in no way distract us from continued efforts to curtail the use of tobacco, which will remain the major causative factor for lung cancer and several other diseases," Varmus said.
A CT scan costs about $300, and wide-scale screening could be very expensive. Currently, Medicare and most private health insurers do not cover CT scans for lung cancer screening. But officials at the Centers for Medicare and Medicaid Services said they would review the findings.
The $250 million study, which started in 2002, involved 53,500 men and women at 33 sites across the country. Participants had to have smoked the equivalent of a pack a day for 30 years. They also had to have no signs or history of lung cancer. The participants were randomly assigned to receive three annual screenings - either CT scans or standard chest X-rays.
The subjects were followed for as long as five years to see who developed lung cancer. If cancer was diagnosed, the patient received standard treatment. There were 354 lung cancer deaths among the subjects who had CT scans, compared with 442 among those who had chest X-rays - a 20.3 percent reduction in lung cancer mortality.
In addition to a reduction in lung cancer deaths among those scanned, the study found a 7 percent reduction in deaths from any cause. It remained unclear why that would be the case, but researchers speculated that it might be attributable to the scans detecting other cancers or illnesses, such as heart or lung disease.