How Switching to E-Cigarettes After Smoking Cessation Affects Lung Cancer Risk

Switching to e-cigarette use after conventional smoking cessation was associated with a higher risk of lung cancer and related mortality, according to a recent study that highlights the “potential harmful effects of alternative e-cigarette use.”

Yeon Wook Kim, MD, of the Seoul National University Bundang Hospital, and colleagues conducted the study and presented their findings during the American Thoracic Society 2024 International Conference.

It was important to conduct the research because e-cigarettes “have gained popularity as a less harmful alternative to conventional cigarette smoking,” but it “remains unclear” if switching to e-cigarette use after conventional smoking cessation affects future lung cancer risk, Dr. Kim and colleagues explained.

To address the questions surrounding e-cigarette use after conventional smoking cessation, the researchers designed a nationwide, population-based study to evaluate lung cancer risk and the related mortality associated with changing from conventional cigarettes to e-cigarette use. Dr. Kim and colleagues further stratified the data by the length of smoking cessation.

The study included more than 4.3 million people who had a history of conventional smoking and had participated in the National Health Screening program in 2012-2014 and 2018. The participants were followed until December 2021.

The researchers categorized participants into 6 groups according to their smoking history and habit change to e-cigarette use as follows:

• People who quit smoking conventional cigarettes at least 5 years prior without e-cigarette use
• People who quit smoking conventional cigarettes less than 5 years prior without e-cigarette use
• People who currently smoke conventional cigarettes without e-cigarette use
• People who quit smoking conventional cigarettes at least 5 years prior with e-cigarette use
• People who quit smoking conventional cigarettes less than 5 years prior with e-cigarette use
• People who currently smoke conventional cigarettes with e-cigarette use

The researchers assessed the risk of lung cancer and lung cancer-specific death using Cox proportional hazards models with adjustments for potential confounders. Dr. Kim and colleagues also conducted stratified analysis for high-risk individuals aged 50-80 years with ≥20 pack-years smoking history who would likely be recommended for lung cancer screening.

During the study follow-up period, 53,354 people developed lung cancer, with 6351 lung cancer-specific deaths reported. People who quit smoking conventional cigarettes at least 5 years prior but used e-cigarettes had an increased risk of lung cancer-specific death compared with those who quit smoking conventional cigarettes at least 5 years prior with no e-cigarette use (adjusted hazard ratio [aHR],2.69; 95% CI, 1.12-6.46).

In addition, people who quit smoking conventional cigarettes less than 5 years prior but used e-cigarettes also had a higher risk of lung cancer development (aHR, 1.23; 95% CI, 1.09-1.39) and lung cancer-specific death (aHR, 1.71; 95% CI, 1.10-2.66) compared with those who quit smoking conventional cigarettes less than 5 years prior with no e-cigarette use.

The stratified analysis of high-risk individuals aged 50-80 years with ≥20 pack-years smoking history showed that people who quit smoking conventional cigarettes at least 5 years prior and had e-cigarette use had a higher risk of lung cancer (aHR,1.65; 95% CI, 1.05-2.58) and lung cancer-specific death (aHR, 4.46; 95% CI, 1.85-10.75) than those who quit smoking conventional cigarettes at least 5 years prior without e-cigarette use.

In addition, people who quit smoking conventional cigarettes less than 5 years prior with e-cigarette use had a higher risk of lung cancer (aHR, 1.26; 95% CI, 1.03-1.54) than those who quit smoking conventional cigarettes less than 5 years prior without e-cigarette use.

Dr. Kim and colleagues concluded by reflecting on the study results and the clinical implications of the findings.

“Switching to e-cigarette use after conventional smoking cessation was associated with a higher risk of lung cancer and related mortality, particularly in high-risk individuals who are likely recommended for low-dose [computed tomography]-based screening,” the presenters explained. “Clinicians must highlight the potential harmful effects of alternative e-cigarette use when integrating smoking cessation interventions to reduce lung cancer risk.”

Reference

Kim YW, Park EJ, Kwak KI, et al. Association of electronic cigarette use after conventional smoking cessation with lung cancer risk: a nationwide cohort study. Presented at the American Thoracic Society 2024 International Conference; May 17-22, 2024; San Diego, California.