A special type of CT scan appears to be able to detect lung cancer early enough to save some lives, U.S. researchers announced Thursday -- offering what could be the first screening test for the devastating disease.
Lung cancer is still the top cancer killer in Canada and the United States. In Canada, an estimated 24,200 new lung cancer cases are expected this year, and only about 15 per cent of those patients will live five years after diagnosis.
Part of the reason the death rate is so high is that typically, when the cancer is discovered, it too late for effective treatment.
No method of screening for lung cancer has ever been found that can reduce death rates. But on Thursday, the National Cancer Institute in the U.S. raised hope, with the announcement of findings from the huge National Lung Screening Trial.
The study enrolled 53,000 people aged 55 to 74 who were or had been heavy smokers. Once a year for three years, the participants were screened for lung cancer -- half were scanned with a standard chest x-ray, while the other half used a special spiral CT scan.
Technically called a low-dose helical CT, the scan uses rotating scanners to view the lungs at various angles to spot growths. They are already routinely used to determine how advanced a cancer is after diagnosis, but aren't used for regular screening.
The study found that "there was a decrease in deaths from lung cancer if you undergo CT screening," said Dr. Claudia Henschke at Mount Sinai School of Medicine in New York.
The scans resulted in 20 per cent fewer deaths from lung cancer among those screened with spiral CTs compared to those given chest X-rays.
The actual number of deaths averted was modest -- 354 died in the spiral CT group over the eight-year study period compared with 442 deaths among those who got chest X-rays. But the difference was significant enough that the researchers decided to end the study early to announce the findings.
"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 per cent has the potential to spare very significant numbers of people from the ravages of this disease," NCI Director Dr. Harold Varmus said in a news release.
Dr. Heidi Roberts, a radiologist at Princess Margaret Hospital in Toronto, said the results could eventually lead to a change in policy on the use of CT scans.
"This is a very significant study," she said. "This is huge."
The NCI said it is not clear that all smokers should get the scans, which carry risks. It notes that the scans frequently mistake scar tissue or some other benign lump for cancer, leading to unnecessary biopsies or surgery. Those interventions carry the risk of a collapsed lung, infection or other problems.
Since CT scans also expose patients to considerably more radiation than standard chest X-rays, there are also questions about whether the radiation exposure changes a smoker's lifetime risk of other radiation-related cancers.
The radiology expert who helped to design the study, Duke University's Dr. Edward F. Patz Jr., said he was far from convinced that a thorough analysis of the study would show benefits from widespread CT screening in preventing lung cancer deaths.
Patz told The New York Times that the size of cancerous lung tumours often tells little about the stage of the disease.
"If we look at this study carefully, we may suggest that there is some benefit in high-risk individuals, but I'm not there yet," Patz said.
The NCI is still compiling rates of false alarms and compiling the radiation risks. It plans to publish a fuller analysis with more detailed results within the next few months in a peer-reviewed journal.
In the meantime, Varmus said the best advice for avoiding lung cancer is to quit smoking.
