FILE - In this June 3, 2010, file photo, Dr. Steven Birnbaum works with a patient in a CT scanner at Southern New Hampshire Medical Center in Nashua, N.H. According to a study released on Wednesday, May 16, 2018, less than 2 percent of eligible current and former smokers have sought free lung cancer screening, five years after government and private insurers started paying for it. (AP Photo/Jim Cole, File)
FILE - In this June 3, 2010, file photo, Dr. Steven Birnbaum works with a patient in a CT scanner at Southern New Hampshire Medical Center in Nashua, N.H. According to a study released on Wednesday, May 16, 2018, less than 2 percent of eligible current and former smokers have sought free lung cancer screening, five years after government and private insurers started paying for it. (AP Photo/Jim Cole, File) Credit: Jim Cole

Lung cancer screening has proved to be stunningly unpopular. Five years after government and private insurers started paying for it, less than 2 percent of eligible current and former smokers have sought the free scans, researchers report.

The study didnโ€™t explore why, but experts say possible explanations include worries about false alarms and follow-up tests, a doctor visit to get the scans covered, fear and denial of the consequences of smoking and little knowledge that screening exists.

โ€œPeople are not aware that this is a test that can actually save lives,โ€ said Dr. Richard Schilsky. โ€œItโ€™s not invasive, itโ€™s not painful, thereโ€™s no prep, nothing has to be stuck into any body cavity,โ€ so to see so little use โ€œis shocking.โ€

Schilsky is chief medical officer of the American Society of Clinical Oncology, which released the study on Wednesday in advance of the groupโ€™s meeting next month.

Lung cancer is the top cancer killer worldwide, causing 155,000 deaths in the United States each year. Itโ€™s usually found too late for treatment to succeed.

A big study found that annual low-dose CT scans, a type of X-ray, could find cases sooner and lower the risk of dying of lung cancer by 20 percent for those at highest risk. Thatโ€™s people ages 55 through 79 who smoked a pack of cigarettes a day for 30 years or the equivalent, such as two packs a day for 15 years.

In 2013, a government task force and others backed screening for such folks. The scans cost $100 to $250 and are free for those who meet the criteria, but people must have a special appointment to discuss risks and benefits with a doctor.

Dr. Danh Pham at the University of Louisville in Kentucky and others got information on how many scans were done from an American College of Radiology registry of all 1,800 sites in the U.S. accredited to perform them. A federal health study was used to estimate how many current and former smokers were eligible.

The results: In 2016, less than 2 percent of 7.6 million eligible smokers were screened. Rates ranged from 1 percent in the West to 3.5 percent in the Northeast.

Thatโ€™s way below the 60 percent to 80 percent rates for breast, colon or cervical cancer screening.

The study was sponsored by the Bristol-Myers Squibb Foundation. One study leader has consulted for the company and other cancer drugmakers.

Mary Baroody, of Alexandria, Va., has had several scans at MedStar Georgetown University Hospital since her husband, Michael, was diagnosed with lung cancer and successfully treated seven years ago.

Both are 71 and longtime smokers who quit 15 years ago.

โ€œIโ€™m glad to go do it and I feel good afterward,โ€ she said of getting screened. โ€œYou get a clean bill of health. What else could you want?โ€

But screening has a dark side: research shows that over three years of annual scans, 40 percent of people will have an abnormal finding that often leads to follow-up tests such as a lung biopsy, and complications of those can be fatal, said Dr. Otis Brawley, the American Cancer Societyโ€™s chief medical officer.