Man vaping
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A large, population-based study carried out in Korea has shown that former smokers who use e-cigarettes, or vaping devices, are significantly more likely to develop or die from lung cancer than those who do not take up vaping when they quit smoking.

The research, presented at the ATS 2024 International Conference, indicated that the risk is particularly among individuals who are already at high-risk for lung cancer and meet the recommended criteria for lung cancer screening.

“This is the first large population-based study to demonstrate the increased risk of lung cancer in e-cigarette users after smoking cessation,” said presenting author Yeon Wook Kim, an assistant professor in the division of pulmonary and critical care medicine, department of internal medicine at Seoul National University Bundang Hospital in Seongnam, Republic of Korea.

He explained that, in recent years, e-cigarettes have gained popularity as a less harmful alternative to conventional cigarette smoking, but their impact on future lung cancer risk is currently unclear.

Biological studies indicate possible dangers of vaping, including pulmonary toxicity and lung cancer. E-cigarettes and heating elements have been shown to contain carbonyl compounds such as formaldehyde, acetaldehyde, acrolein, and diacetyl, and toxic metals including chromium, nickel, and lead, which are known to be carcinogenic. These toxins are also present in conventional cigarettes.

Kim and co-workers investigated the link between e-cigarette use and lung cancer risk in former smokers using data from Korea’s National Health Screening Program. The study included more than four million individuals who took part in the program during its first (2012–2014) and second (2018) periods and were followed up until December 2021.

The participants were categorized into six groups according to their smoking history and habit change to e-cigarette use:

  1. Ex-smokers five or more years since quitting (YSQ) without e-cigarette use
  2. Ex-smokers five or more YSQ with e-cigarette use
  3. Ex-smokers less than five YSQ without e-cigarette use
  4. Ex-smokers less than five YSQ with e-cigarette use
  5. Current smokers with e-cigarette use
  6. Current smokers without e-cigarette use

During follow-up, 53,354 individuals developed lung cancer and there were 6,351 lung cancer-specific deaths.

The researchers found that ex-smokers who were at least five YSQ and used e-cigarettes were a significant 2.7 times more likely to die from lung cancer than those who were at least 5 YSQ but did not use e-cigarettes.

In addition, ex-smokers who were less than five YSQ and used e-cigarettes had a significant 1.2-fold higher risk for developing lung cancer and a 1.7-fold higher risk for dying of lung cancer than those who were less than five YSQ and did not use e-cigarettes.

The team also carried out a subgroup analysis among individuals who would likely be eligible for lung cancer screening according to the 2021 US Preventive Services Task Force (USPSTF) criteria and the 2023 American Cancer Society (ACS) guidelines, i.e. those aged 50–80 years with a smoking history of at least 20 pack–years.

This revealed that the risks for lung cancer and lung cancer specific death were significantly higher among all participant categories when compared with individuals who had stopped smoking five or more years ago and did not use e-cigarettes.

However, the highest risks occurred among ex-smokers at least five YSQ with e-cigarette use. This group had a significant 1.7-fold higher risk for developing lung cancer and a 4.5-fold higher risk for lung cancer specific death than the group at least five YSQ without e-cigarette use.

“The fact that e-cigarette use showed association with increased lung cancer among this group was most surprising and the most important message of our study,” Kim told Inside Precision Medicine.

In addition, ex-smokers less than five YSQ with e-cigarette use who met the screening criteria had a significant 1.3-fold higher risk of lung cancer than those less than five YSQ without e-cigarette use.

“Our results indicate that when integrating smoking cessation interventions to reduce lung cancer risk, the potential harms of using e-cigarettes as an alternative to smoking must be considered,” said Kim.

He added that the team now plans to extend the follow-up period of the study as longer term data becomes available and also look more specifically at the type of e-cigarette used and the duration of conventional smoking cessation.

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