Researchers have developed a new assessment tool that may help predict the personal risk of developing lung cancer among light tobacco smokers, as well as people who never smoked — populations that are not included in routine lung cancer screenings of heavy smokers.
Although the findings sound promising, the model was built on data from a group of people in Taiwan. So, considering the impact of genetics, the model now needs to be confirmed in more ethnically diverse groups to be generally applicable.
The study, “Personalized Risk Assessment in Never, Light, and Heavy Smokers in a prospective cohort in Taiwan,” was published in the journal Scientific Reports.
Despite the strong link between smoking and lung cancer, the fact remains that about 20% of lung cancers in the U.S. are diagnosed in people who do not smoke. Little is known, however, about factors that may increase the risk of lung cancer in people who are not heavy smokers.
To be included in lung cancer screening, a person needs to have smoked more than one pack per day for 30 years (referred to as 30 pack-years), and be between 55 and 74 years old. For people not meeting the criteria, there currently is no way of knowing if an individual is at high risk of lung cancer and be included in screening efforts.
This also is mirrored by the fact that only about one-third of those who end up with lung cancer met the current criteria for screening.
To get a better picture of the factors influencing lung cancer risk, researchers at the University of Texas M. D. Anderson Cancer Center analyzed a cohort of 395,875 individuals recruited by MJ Health Group to participate in a health-screening program in Taiwan.
Participants were on average 40.4 years old and 52% were women. The research team divided the group into heavy smokers, who had a history of 30 pack-years or more, light smokers, who had smoked less than 30 pack-years, and those who never smoked.
The study followed participants for a median 7.3 years. In this time, 1,117 patients were diagnosed with lung cancer, at an average age of 60.2 years old.
The study found that an astonishing 47% of the lung cancers were diagnosed in people who never smoked, and 38% of the cancer patients were women.
To see what factors impacted the results, researchers incorporated information about age, gender, smoking history, personal and family cancer history, body mass index, results of a lung function test and four blood biomarkers into a statistical model.
The study confirmed what clinicians had suspected; some people who had never smoked had a higher risk of developing cancer than heavy smokers. The five-year estimated risk ranged from .01% to 15.8% in never smokers, 0% to 7.4% in light smokers, and .02% to 7.5% in heavy smokers.
Over 10 years, estimated risks reached 33% in some people who never smoked, 16% in light smokers, and 18% in heavy smokers.
“Our model was able to stratify light and never smokers into groups with dramatically different probabilities of developing lung cancer over time,” Xifeng Wu, MD, PhD, professor of Epidemiology and first author of the study, said in a news release. “According to our results, a small number of never smokers have lung cancer risks as high as some heavy smokers.”
The findings underscore the need to take alternative factors into account when recommending lung cancer screening. This would allow not only inclusion of people who are not considered for screening today, but also reduce unnecessary screening in smokers who are not at high risk.
To assess if the model also is suitable for non-Asian populations, Wu and his research team are now working to identify suitable patient groups for future studies.