Low-dose CT scans cut lung cancer deaths 20 percent

The National Cancer Institute and the American College of Radiology Imaging Network tested a newer option, low-dose CT scanning, in a massive trial of current and former heavy smokers who faced the highest lung cancer risk in the country.

The National Lung Screening Trial randomly assigned 53,454 people aged 55 to 74 with heavy smoking histories to annual low-dose CT or chest X-ray for three years. Those screened with CT were about 20 percent less likely to die of lung cancer.

The result changed screening guidelines nationwide, but the trial also exposed real costs: roughly a quarter of CT scans flagged something that turned out not to be cancer, leading to extra tests and sometimes unnecessary procedures, and a later analysis found some detected tumors would never have caused harm if left alone. A European trial, NELSON, later confirmed the benefit with an even larger relative reduction.

Three scans, about three fewer deaths per thousand.