Low-dose computerized tomography -- or CT -- scans better detect earlier stages of lung cancer than a standard chest X-ray, significantly cutting deaths from the disease, the National Cancer Institute announced today.
The NCI's study enrolled 53,000 current and past smokers who were screened annually for three years by either CT scan or conventional chest X-rays and found those who were screened CT were 20 percent less likely to die from lung cancer.
In a teleconference today, trial investigators said they presumed CT scans were able to detect smaller tumors, which led to an earlier diagnosis and subsequently earlier intervention.
"This has the potential to save many lives among those at risk for lung cancer," said Dr. Harold E. Varmus, director of the National Cancer Institute, at the teleconference.
The trial, which began in 2002, ended earlier than expected after the Data Safety Monitoring Board, an independent panel of reviewers, found there was sufficient data collected to show a significant decrease in lung cancer death in participants who underwent CT screening.
Lung cancer is the major cause of death from all cancers in United States, said Varmus. It will cause 157,000 deaths in U.S. this year, he said.
A CT scan uses multiple X-ray views to assemble cross-sectional images of structures inside the body. Because its use involves several X-ray scans, it generally exposes patients to nearly three times the degree of radiation than a single X-ray.
Still, investigators said the amount of radiation in a low-dose scan such as the one used is almost equivalent to a standard mammography, which is used to detect breast cancer.
Despite seemingly positive results, investigators at the teleconference said CT scans also pose many hurdles. According to Dr. Douglas Lowy, laboratory chief and principal investigator at the National Cancer Institute, while a CT may detect a tumor earlier, more tests will be needed to track the tumor and treat if necessary.
"Subsequent procedures are always needed to evaluate for a diagnosis," which can include follow up scans, biopsies, and surgery to remove potentially cancerous tumors, said Lowy.
And while Varmus noted CT scans may be better able to detect smaller tumors, it's likely the tumors would not have grown to be cancerous.
"Simply identifying a tumor at an early stage is not saying that CT is an effective modality," said Varmus.
Scan results that show tumors may lead experts to mistakenly detect lung cancer, he said.
However, according to Dr. Claudia Henschke, professor of radiology and chief of the Chest Imaging Division of the Weill-Cornell Medical Center at New York-Presbyterian Hospital, many experts can avoid over-diagnosing and over-treating patients by using the scan to monitor tumors over time.
"Every year after you calculate how fast the tumor is growing," said Henschke.
For now patients would bear the cost for screening. CT scans, which cost about $300, are covered by some insurance companies to diagnose cancers. But insurance companies do not cover scans as a method to screen for the disease.
However, according to Henschke, early detection of tumors through CT scans -- which can lead to earlier diagnosis and treatment of lung cancer -- is worth the price.