许多医疗设施，包括约翰霍普金斯医院和马里兰Greenebaum大学癌症中心，有可能开始更经常使用CT扫描的高风险患者。所涉及的技术是所谓低剂量螺旋CT成像。该技术比传统的胸部X光敏感，病人的X光辐射 与传统乳房X光检查大致相同.
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CT scans can reduce lung cancer deaths, study says
Tests are better than X-rays at finding tumors earlier
By Meredith Cohn, The Baltimore SunCT scans can reduce deaths by 20 percent in older, heavy smokers by detecting tumors earlier, according to results released Thursday from an eight-year-long national study.
The study, sponsored by the National Cancer Institute and launched in 2002, aimed to see if the tests, which are more sensitive than X-rays, would affect the outcomes for those withlung cancer, the leading cause of cancer-related deaths in the country.
The disease was estimated to have killed 159,390 people in 2009, according to the institute — more people than killed by breast, prostate, colon and pancreatic cancer combined.
Many medical facilities, including Johns Hopkins Hospital and the University of Maryland Greenebaum Cancer Center, are likely to start using the scan more regularly on high-risk patients. Already, some study participants are touting it.
The 65-year-old Baltimore woman was one of 1,684 Hopkins participants, and after her first scan in 2003 doctors noticed something amiss. Five years after surgery, she's cancer-free and wants to get the word out about the scans — and send a message to quit smoking, the top risk factor for the cancer.
That's also the message that officials hope to send by releasing the early data from the study, a randomized clinical trial that began in 2002 with 53,000 current and former heavy smokers who were screened at 30 sites.
Many lung cancers are not detected until they have spread, but a CT scan can not only detect a problem in high-risk patients early enough to treat it, but also improve the chances of long-term survival, said Dr. Harold Varmus, the institute director, during a news conference.
The doctors involved in the study have sent letters to the participants who had X-rays saying that they should talk to their health care provider about a CT scan.
Varmus warned that the results only apply to these older, long-time smokers. And there is much that the study did not address, such as how often a test would be needed. There also are other drawbacks. The test is not covered by most insurance or Medicare. It exposes patients to more radiation than X-rays, and it produces more false positive results that can lead to more unnecessary procedures and anxiety.
Even with the limitations, he called the results significant.
"Lung cancer is the leading cause of cancer mortality in the U.S. and throughout the world, so a validated approach that can reduce lung cancer mortality by even 20 percent has the potential to spare very significant numbers of people from the ravages of this disease," he said.
He added, "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."
Not all lung cancer is a result of smoking, but with 90 million current and former smokers around the nation at higher risk of developing lung cancer, finding a way to diagnose and treat them has become a priority, according to the institute.
Now, most lung cancers are detected when there are symptoms, such as a persistent cough. It's spread outside the lung in up to 30 percent of cases, according to the institute. The CT scan, first used in the 1990s, is better at finding small cancers before they have spread because many more images are taken than with an X-ray, said Dr. Elliot Fishman, professor of radiology, surgery and oncology at Hopkins.
An X-ray offers one image, and what can be seen is limited, he said. A CT scan takes more than 300 "slices," each 0.75 millimeters thick, which show even small tumors. They also show nodules that developed during past infections, for example, which is why other tests become necessary, he said.
Doctors already use CT scans to find other cancers such as colon cancer, and already knew that they were more sensitive and better at helping diagnose lung cancer. But the $300 scans weren't routinely used for screening for lung cancer because there wasn't evidence that patient outcomes were better.
Fishman believes now they will be used more on long-time smokers who are at higher risk for lung cancer, even given the drawbacks. After the data is published and further reviewed, insurance also is likely to cover the practice for high-risk patients. However, he said there is still likely to be debate, as there is with most preventative tests.
"What the study ended up showing was that it does make a difference," Fishman said. "It's very positive. Twenty percent is significant. ...The bottom line is it's easy enough and cheap enough that we should just do it."
Still left to decide, he said, is how often to do CT screenings. If nothing is found in a scan, he said, he's likely to recommend no less than three years because most lung cancers grow slowly. That would put the test somewhere between annual mammograms and colonoscopies that are done every 5 years or more.
There will be more research over the next couple of years, noted Fishman and Dr. Martin Edelman, a professor of medicine at the University of Maryland School of Medicine and director of solid tumor oncology at Maryland's Greenebaum Cancer Center.
But Edelman, who helped verify the cancer study's results, said the findings were definitive and many facilities are likely to begin scanning high-risk patients for lung cancer immediately. He said his cancer center will.
He said the risk of death is reduced about the same amount as mammography reduces risk of death frombreast cancer. And while it's not a cure, this scan, as well as advances in treatment, will surely give more people more time.
"There will be demand for this," he said. "It's likely to emerge as a standard of care for that population. ... It still doesn't mean it's safe to go out and smoke."
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The long-awaited results of the trial involving more than 53,000 former and current heavy smokers were so conclusive that the study was terminated ahead of schedule last week and letters were sent to all the participants advising them of the results.
The findings are considered a major step forward in fighting the most deadly form of cancer — which is expected to kill an estimated 157,000 Americans this year — because chest X-rays have never been proven to be an effective tool for identifying tumors. CT scans are more powerful and provide a much clearer picture of the lungs.
At least 85% of lung cancer deaths occur in smokers or former smokers. By the time symptoms develop, the cancer has often spread to the point that it is difficult to treat.
"This is the first clear demonstration that a screening procedure can be effective in reducing deaths from lung cancer," Dr. Douglas Lowy of the National Cancer Institute, which sponsored the $250-million study, said in a telephone news conference from Bethesda, Md.
The study "has important implications for public health," added Dr. Harold Varmus, director of the National Cancer Institute, "but no one should believe that it is safe to continue to smoke or to start smoking. We can reduce deaths by 20%, but screening does not prevent lung cancer or prevent the large majority of deaths from lung cancer."
Varmus said the scientists were still analyzing all the data and hoped to prepare a scientific paper for publication within the next few months.
He also noted that the researchers were not making any recommendations about whether routine screenings should be conducted in any group. Such recommendations should not be made until the full analysis is complete, he said, and are usually made by other groups, such as the U.S. Preventive Services Task Force.
Dr. Otis W. Brawley, chief medical officer of the American Cancer Society in Atlanta, said the group would take the new findings into account in its future recommendations, but only after they were published and reviewed by independent experts. Until then, he said in a statement, "the best advice we can give is to encourage people to have conversations with their doctors about whether lung cancer screening is right for them."
The technology involved in the screening is called low-dose spiral CT imaging, in which a complete three-dimensional image of the chest cavity can be produced during the duration of one held breath. The technology is much more sensitive than a conventional chest X-ray, but also exposes the patient to much more radiation — about the same amount associated with a conventional mammogram, according to Dr. Denise R. Aberle of UCLA's Jonsson Comprehensive Cancer Center, the principal investigator of the study.
A typical spiral CT costs between $300 and $1,000 and, unless it is for diagnostic purposes, is not paid for by insurers.
Participants in the study were enrolled at 33 sites nationwide in 2002 and 2003. Each was between the ages of 55 and 74 at the beginning of the study and had smoked the equivalent of a pack a day for 30 years. Subjects were randomized to receive either yearly chest X-rays or yearly spiral CTs for three years, then monitored for the duration of the study. Lung cancer deaths were confirmed by a panel of experts.
By Oct. 20, a total of 354 lung cancer deaths had occurred among those in the CT arm of the study, compared with 442 in the chest X-ray group — a difference too large to be due to chance. Deaths from any cause, including lung cancer, were reduced by 7% in the CT group. The data-monitoring board concluded that the study had met its goal and sent a letter to Varmus on Oct. 28 recommending that the study be stopped.
"This is some of the best news we've had in a decade," said Dr. Bruce E. Johnson, a thoracic oncologist at the Dana-Farber Cancer Institute in Boston. "I've been treating lung cancer patients for 35 years, and 85% die of it. Cutting that down by 20% is a pretty big event."
Despite the success, Lowy cautioned that there could be some downsides to screening. In addition to cost, there is the problem of false positives. About 25% of the CT subjects in the study had false positives. Many of those were cleared up by additional diagnostic CT scans, which showed the abnormalities to be scarring or other artifacts, but some required lung biopsies, which proved unnecessary.
Also, he said, "it remains to be determined if the radiation doses increase the risk of cancer over the remainder of the participants' lifetimes."
