"What we're finding with CT screening are more early-stage cancers", said Stephen J. Swensen, M.D., professor and chair of the Department of Radiology at Mayo Clinic in Rochester, Minn. "However, a number of these are probably non-lethal or slow-growing cancers that the patient would likely have died with and not from. Other cancers were so aggressive that early detection with CT did not make a difference."
While recent studies have focused on the benefits of early detection, the Mayo researchers looked more closely at the negative impact of CT screening, including over-diagnosis, expense, changes to quality of life, unnecessary surgical procedures and mortality.
Between January 1999 and May 2004, Dr. Swensen and colleagues studied 1,520 current and former smokers at high risk for lung cancer. The patient group contained 788 men and 732 women, age 50 or older. All patients received an initial low-dose, helical CT examination, with annual screenings over the next four years.
The researchers documented 68 primary lung cancers in 66 patients. Thirty-one of the tumours were detected at the initial screening and 34 at subsequent screenings. Three cancers were diagnosed by other means between screenings.
Approximately 69 percent of patients had at least one false-positive finding. Among the cancers identified through CT screening, false-positive rates ranged from 92.4 percent among nodules 4 millimeters or larger to 96 percent among all nodules.
"Currently, half of lung nodules suspected of being cancerous that go to surgery outside of research study centres turn out to be benign," Dr. Swensen said.
MEDICA.de; Source: Radiological Society of North America