Despite a study published last year that found screening heavy smokers with early CT scans reduces deaths from lung cancer, health care experts continue to debate whether the tests should be widely used, according to USA Today.

The study of more than 50,000 heavy smokers with no symptoms of lung cancer, published in the New England Journal of Medicine, found deaths among those screened with low-dose helical CT scans were 20 percent lower than those screened with chest X-rays.

Because most lung cancers don’t cause symptoms early in the course of the disease, the majority of lung cancer cases are detected only after the disease has spread, the article notes.

The American Cancer Society and most other medical groups do not recommend widespread CT screening for heavy smokers. They point to potential downsides of the test, such as false positives that lead to additional testing, and premature deaths caused by procedures prompted by the screenings, such as needle biopsies of the lung.

The American Cancer Society recommends heavy smokers who are interested in screening should discuss the potential benefits and risks with their doctor. “It saves lives, but it also costs lives,” said Dr. Otis Webb Brawley, said Chief Medical Officer and Executive Vice President of the American Cancer Society.

The health insurer WellPoint decided in November that the CT scans were medically necessary for an estimated 250,000 of their policy holders. The company now allows for a screening test every year for three years, at a cost to the policy-holder of between $150 and $300.