Smoke screen: What should be done about CT lung cancer screening criteria?

When the Centers for Medicare and Medicaid Services (CMS) approved coverage of annual low-dose CT lung cancer screening for high-risk beneficiaries, it felt like the end of a long-running debate over who should undergo screening. However, a recent top story has shown that the conversation is far from over.

A study published in the Feb. 24 edition of the Journal of the American Medical Association suggested that the current guidelines on who should be eligible for screening may miss the mark. Based on screening criteria set by the U.S. Preventative Services Task Force and following results of the National Lung Screening Trial, CT screening is recommended for asymptomatic adults age 55 to 80 who have smoked for 30 pack-years (one pack per day for 30 years) and are still smoking or have quit within the last 15 years.

The catch? As smoking rates decline, the number of people eligible for screening is falling as well. Ironically, the great public health victory of limiting smoking rates may prop up lung cancer mortality rates as patients who would have had their cancers diagnosed early are denied the opportunity to screen.

That’s the argument from study author Ping Yang, MD, PhD, an epidemiologist at Mayo Clinic Cancer Center in Rochester, Minn. She and colleagues conducted an analysis of a local database featuring information on lung cancer rates for a population of about 140,000 across a 27-year timespan. They found that among the 1,351 people who developed lung cancer during that time, the number of patients with a 30 pack-year smoking history declined and the number of those who were smoke-free for 15 years increased. As a result, the percentage of those who would’ve qualified for CT screening fell from 57 percent between 1984-1990 to 43 percent between 2005-2011.

“As smokers quit earlier and stay off cigarettes longer, fewer are eligible for CT screening, which has been proven effective in saving lives,” Yang said in a statement. She went on to say that she is aware of many smokers who continue to smoke just to remain eligible for CT screening.

This is a backwards scenario that should not continue, but fixing it will not be easy. While patients should not be punished for kicking their smoking habit, there is likely little willingness to expand eligibility criteria. Relaxing the requirements too much will increase costs and raise concerns about radiation exposure and overtreatment of false positives. Simply getting Medicare coverage this far was a battle. Prior to CMS’ decision, some experts had argued there wasn’t enough data to extend coverage in the first place.

Refining lung cancer screening eligibility will take additional research into identifying more sensitive screening criteria, such as genetic or physiological markers of disease.

That research will take time, but while we wait, let’s hope that fewer people regard a continuation of smoking as a ticket to undergo screening.

-Evan Godt
Editor – Health Imaging