Lung cancer screening guidelines may harm ex-smokers

Volume 4, Issue 2, 2015


People who could benefit from early detection of lung cancer don't qualify for CT scans.

Photograph of Ping Yang, M.D., Ph.D.

Ping Yang, M.D., Ph.D.

Many people who quit smoking and could have benefited from early detection of lung cancer may actually be dying because they don't qualify for low-dose CT scans, according to a group of Mayo Clinic Cancer Center researchers.

Their research was published in the Feb. 24, 2015, issue of JAMA.

"As smokers quit earlier and stay off cigarettes longer, fewer are eligible for CT screening, which has been proven effective in saving lives," said Ping Yang, M.D., Ph.D., an epidemiologist at the Mayo Clinic Cancer Center. "Patients who do eventually develop lung cancer are diagnosed at a later stage, when treatment can no longer result in a cure."

Dr. Yang said researchers and policymakers need to re-examine screening criteria to identify a greater proportion of patients who will develop lung cancer.

The study retrospectively tracked about 140,000 residents of Olmsted County in Minnesota who were older than 20 from 1984 through 2011. Lung cancer cases were identified using the Rochester Epidemiology Project database and confirmed by pathology definition of the World Health Organization.

Researchers determined the proportion of patients with lung cancer who would have met lung cancer screening criteria set by the U.S. Preventive Services Task Force. Those criteria, used by doctors and insurance companies, recommend CT screening for asymptomatic adults ages 55 to 80 who have smoked at least 30 pack-years (one pack a day for 30 years), and are still smoking or have reduced smoking in the last 15 years.

A total of 1,351 people in the study developed primary lung cancer between 1984 and 2011. Researchers found that the incidence of primary lung cancer declined overall during the study period — but only for men and only by about one-third.

Among women, the incidence of lung cancer rose 8 percent, despite a decline in the proportion of patients with lung cancer who had smoked at least 30 pack-years and an increase in the proportion of patients with lung cancer who had quit smoking for more than 15 years.

"While more people have quit for a longer period of time, they are still getting lung cancer," Dr. Yang said. "And they make up a larger proportion of newly diagnosed lung cancer patients."

As a result, the percentage of patients with lung cancer who would have been eligible for screening fell steadily during the study period — from 57 percent in the 1984-1990 span to 43 percent in the 2005-2011 span. The percentage of women who would have been eligible for screening under the criteria decreased from 52 to 37 percent, and among men from 60 to 50 percent.

This means that many more patients could miss out on early detection of lung cancer, which could increase their risk of death. Treatment of lung cancer is most successful when the lung cancer is detected early.

Dr. Yang hopes to see screening criteria adjusted to include smokers who have smoked less than 30 pack-years and those who quit more than 15 years ago.

"We don't want to penalize people who succeeded in smoking cessation," she said.