By Sharon Begley
NEW YORK, May 7 (Reuters) - Stepping into the debate over who should be screened for lung cancer, a leading medical specialty group issued new guidelines on Tuesday recommending that doctors offer annual low-dose CT (computed tomography) scanning to people whose age and smoking history puts them at significant risk of lung cancer.
That means current smokers aged 55 to 74 with more than 30 pack-years of smoking, or former smokers with that profile who have quit within the last 15 years, said the American College of Chest Physicians.
That was the population in whom the largest-ever lung-cancer-screening study, the National Lung Screening Test, found CT screening cuts deaths from lung cancer.
A pack-year is a measure defined as smoking 20 cigarettes a day for a year or any equivalent, such as two packs a day for six months.
That describes an estimated 7 million people, says chest physician David Midthun of the Mayo Clinic.
The NLST, which studied 53,000 current or former heavy smokers, concluded in 2011 that CT scanning reduced mortality from lung cancer in this high-risk group by 20 percent compared to no screening or to X-rays. CT finds small cancers, which can be cured with surgery, that X-rays cannot.
But other medical groups that have weighed in on annual CT screening for lung cancers cast a wider net. Last year, for instance, the National Comprehensive Cancer Network (NCCN) recommended that people 50 (not 55) or older who have at least 20 (not 30) pack years of smoking plus one additional risk factor, such as having chronic obstructive pulmonary disorder or a close relative with lung cancer, also be screened.
Experts are divided on how primary care physicians will implement the recommendations. One concern is that CT screening for lung cancer will proliferate like PSA tests for prostate cancer, which are often given for free in such non-medical settings as sports events.
Marketing for such mass screenings encourage men to get a test that, experts from the American Cancer Society to the American Urological Association now agree, should not be routinely offered to most men, since it leads to biopsies and surgeries that can cause impotence and incontinence but prevents few deaths from prostate cancer.
"Where we have to be wary," said Dr Frank Detterbeck, chief of thoracic surgery at Yale University School of Medicine, who helped develop the screening guidelines for the College of Chest Physicians, "is with entrepreneurs who decide to offer CT screening for free," as some medical centers are already doing.
That may seem like a generous public service, but Detterbeck says there is an "inherent conflict" in taking a loss up front and planning "to make up for it with profits from tests and procedures on things that you find. The problem is that you find a lot of things with screening," but about 97 percent "are nothing. So (free screening) creates pressure to intervene more frequently, whereas doing the right thing dictates that you only intervene when it is really suspicious for cancer."
Lung cancer kills more people in the United States than any other cancer, claiming just under 160,0000 lives each year, more than breast, colon, prostate and pancreatic cancer combined. Only 16 percent of patients live five years after their diagnosis, an indication of how ineffective treatments are.
By the time most patients are diagnosed, the cancer has spread to such organs as the bones and brain. In contrast, early-stage lung cancers "have not metastasized, so surgery is more likely to bring a complete elimination of disease," said Mayo's Midthun.
CT screening is not without risks, however, which is why some experts are concerned about mission creep. Physicians expect worried smokers who fall just outside the new guideline - a 54-year-old with 30 pack-years, for instance - to press their physicians for CT screening, which costs several hundred dollars.
"Requests for CT screening from smokers slightly outside the (chest physicians') new guidelines is an issue we'll face," said Dr Peter Mazzone, a lung specialist at the Cleveland Clinic. "All you can do as a physician is try your very best to stick to the parameters."
Doing otherwise, by offering CT screening to people at lower risk for lung cancer, will find many more suspicious nodules but prevent many fewer lung cancer deaths, tipping the balance toward greater risk than benefit.
"You find a lot of things and most of them are nothing," said Detterbeck.
Nevertheless these can cause worry, additional testing and an invasive biopsy, which is often done via a long needle inserted through the chest wall. Another risk is that CT itself can itself cause lung or breast cancer.
On the benefit side, the NLST found that the number of high-risk smokers who had to be screened with CT to save one person from dying of lung cancer was 320. This compares to 780 women who need to get a screening mammogram for one to be saved from dying of breast cancer. (Editing by Eric Walsh)