Lung Cancer Cases In Never-Smokers On The Rise: Lancet Study

Cases of lung cancer among those who never smoked is on the rise and air pollution could be contributing to the increase, according to a new study.

The study was published in The Lancet Respiratory Medicine journal on World Cancer Day on Tuesday.

Researchers, including those from the International Agency for Research on Cancer (IARC), World Health Organization, analysed data, including those from the Global Cancer Observatory 2022 dataset, to estimate national-level lung cancer cases for four subtypes -- adenocarcinoma, squamous cell carcinoma, small- and large-cell carcinoma.

They found that adenocarcinoma -- a cancer that starts in glands that produce fluids such as mucus and digestive ones -- has become the dominant subtype among both men and women.

The sub-type of lung cancer was also found to account for 53-70 per cent of lung cancer cases in 2022 among never-smokers around the world.

Compared to the other sub-types of lung cancer, risk of adenocarcinoma is considered to be weakly related with cigarette smoking, the authors explained.

"As smoking prevalence continues to decline in many countries worldwide, the proportion of lung cancer in people who have never smoked has increased," they wrote.

"Changes in smoking patterns and exposure to air pollution are among the main determinants of the changing risk profile of lung cancer incidence by subtype that we see today," lead author Freddie Bray, head of the cancer surveillance branch at IARC, said.

Lung cancer is the leading cause of cancer-related deaths.

However, "lung cancer in people who have never smoked is estimated to be the fifth leading cause of cancer-related mortality worldwide, occurring almost exclusively as adenocarcinoma and most commonly in women and Asian populations," the authors wrote.

"In 2022, we estimated that there were 908 630 new cases of lung cancer worldwide among female individuals, of which 541 971 (59.7 per cent) were adenocarcinoma," they wrote.

Further, among the women diagnosed with adenocarcinoma, 80,378 could be traced to ambient particulate matter (PM) pollution in 2022 globally.

"The diverging trends by sex in recent generations offer insights to cancer prevention specialists and policy-makers seeking to develop and implement tobacco and air pollution control strategies tailored to high-risk populations," Bray said.

As of 2019, almost everyone in the world is estimated to live in areas not meeting the WHO air quality criteria. 

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