Purdue Public Health research makes case for new duration-based lung cancer screening policy for current and past smokers

Written By: Rebecca Hoffa, rhoffa@purdue.edu

While breast cancer and colon cancer screenings have become commonplace throughout the years, lung cancer screenings have continued to remain low, with only 18.7% of eligible people in the U.S. getting screened, according to 2025 data from the American Cancer Society.

Pianpian Cao(Photo provided)

Pianpian Cao, assistant professor in the Purdue University Department of Public Health, is looking for screening methods to reduce lung cancer mortality while also investigating interventions to reduce overall lung cancer incidence.  

“Although my work is very quantitative, the motivation is very practical — to inform policy decision-making,” Cao said. “I study questions like: Who should be eligible for lung cancer screening? How often should people go for lung cancer screening if they’re eligible? What kind of primary prevention intervention can be embedded within lung cancer screening programs, such as smoking cessation intervention, to make it more beneficial for the population?”

The current screening environment in the United States focuses on “pack years,” a number calculated by multiplying the number of cigarette packs smoked per day by the number of years spent smoking. The current guidelines for insurance coverage for lung cancer screening are for individuals ages 50-80 who have at least 20 pack years of smoking and have quit within the last 15 years or are currently smoking.

“The lung cancer screening guideline is a little different from the breast cancer screening or colorectal cancer screening,” Cao said. “With those types of screenings, people age into it, so as long as you reach a certain age, you’re eligible. But for lung cancer screening, it’s a little different. There is a set of guidelines that are in place so that if you meet the guideline, you’re eligible, and you can receive screening under insurance coverage.”

In a 2026 study funded by the National Cancer Institute and done in collaboration with the Cancer Intervention and Surveillance Modeling Network (CISNET) Lung Working Group, Cao is looking at evaluating the impact of replacing the pack-year criteria with smoking duration, which may provide a simpler method for determining lung cancer screening eligibility.

“There are some implementation issues with pack years,” Cao said. “It’s really hard to calculate and use in real clinical settings. Clinicians or nurses need to know when someone started smoking, when they quit if they did, and how many cigarettes they smoked per day. That’s a lot of information to collect accurately during a short primary care visit. There’s also a bigger issue: Smoking intensity changes over time. Someone might smoke heavily in their 20s and much less later on, or vice versa. A single number often doesn’t capture that full history very well. Smoking duration, on the other hand, is much more stable and easier for people to recall.”

“Pack years also kind of treat smoking duration and intensity equally. So, it’s telling us that duration and smoking intensity play an equal role in affecting lung cancer risk, but actually they don’t. People who smoke longer but at a lower intensity might be at a higher risk than people who smoke for a shorter time but at a higher intensity, even though the pack year is the same.”

For Cao, the purpose of this research aims to use microsimulation modeling to determine how various screening strategies, including duration-based, pack-year-based and risk-based, would perform in terms of long-term benefits and harms. Cao and the CISNET Lung team ultimately found a 35-year duration-based cut-off was ideal for maximizing benefits, reducing lung cancer mortality and gaining life-years, and mitigating harms, such as false positives or invasive procedures.

“A previously proposed 20-year duration threshold may appear more inclusive, but our findings show it is substantially less efficient,” Cao said. “Compared with current guidelines, it would greatly increase the number of people screened by about 50%, while resulting in only about an 11% increase in health benefits.”

“The work actually moves the conversations beyond eligibility alone and toward understanding the long-term health outcomes of different lung cancer screening strategies,” Cao said. “By projecting both the long-term benefits and harms, it can provide evidence to guide more informed screening policy decisions.”

Cao’s interest in cancer prevention and early detection began during her undergraduate years at Purdue University, where she studied Mathematics and Statistics. As she explored ways to combine her quantitative training with an interest in cancer research, she was introduced to epidemiology through Purdue’s Career Center and recognized it as a field where data-driven approaches could directly inform public health decisions. She later pursued epidemiology to apply modeling methods to improve cancer screening and prevention policies.

Cao sees the potential of duration-based screening to raise the number of individuals who participate in lung cancer screening.

“One potential advantage of duration-based screening is that it might be easier to apply in clinical practice, and so it might be easier to determine eligibility, and that might result in higher uptake, but this is something that we need to study,” Cao said.

Cao is also looking at ways to integrate smoking cessation into the screening process — an area that shows promise in helping to reduce the number of lung cancer incidence before they occur.

“What we found is compared to lung screening without the cessation intervention piece, the joint cessation and screening program may prevent lung cancer and also prolong life by reducing tobacco-related disease and conditions, and thus may be cost-saving compared to screening alone,” Cao said.