Lung cancer in people who have never smoked is now estimated to be the fifth highest cause of cancer deaths worldwide. Lung cancer is still the leading cause of cancer incidence and mortality worldwide, with about 2.5 million people diagnosed with the disease in 2022 alone. But adenocarcinoma is now the dominant subtype particularly in women, a new study finds.
While lung cancer incidence rates among men have generally decreased in most countries during the past 30–40 years, rates among women have continued to rise.
The explanation for this may be air pollution.
This data comes from work done by scientists from the International Agency for Research on Cancer (IARC). They analyzed global variations in lung cancer incidence in 2022 and over time according to histological subtype.
Their study was published this week in The Lancet Respiratory Medicine. The study focused on four main lung cancer subtypes: adenocarcinoma, squamous cell carcinoma, small-cell carcinoma, and large-cell carcinoma.
Drawing mainly on national Global Cancer Observatory (GLOBOCAN) incidence estimates for 2022 and recorded data included in successive volumes of the Cancer Incidence in Five Continents series (Volumes VII–XII), the study shows that lung adenocarcinoma has emerged as the predominant subtype in recent years, with increasing risks observed among younger generations, particularly females, in most countries assessed.
“This population-based study seeks to better understand variations in lung cancer incidence by place and time according to its constituent subtypes. We examine changes in risk in different countries across successive generations and assess the potential burden of lung adenocarcinoma linked to ambient PM pollution,” said Freddie Bray, head of the Cancer Surveillance Branch at IARC and lead author of the article.
“The results provide important insights as to how both the disease and the underlying risk factors are evolving, offering clues as to how we can optimally prevent lung cancer worldwide.”
In 2022, there were an estimated 2,480,675 new cases of lung cancer worldwide. Of the estimated 1,572,045 new cases among men, 45.6% were adenocarcinoma.
Among women, there were an estimated 908,630 new cases of lung cancer worldwide of which 59.7% were adenocarcinoma.
Geographical variations in 2022 in men, the highest age-standardized incidence rates (ASRs) were in East Asia for adenocarcinoma (27.12 per 100,000 people), in eastern Europe for SCC (21.70 per 100,000 people) and small-cell carcinoma (9.85 per 100,000 people), and in North Africa for large-cell carcinoma (4.34 per 100,000 people).
Globally, an estimated 114,486 adenocarcinoma cases among men and 80,378 among women were attributable to ambient PM pollution, corresponding to ASRs of 2.35 per 100,000 men and 1.46 per 100,000 women.
“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,” said Bray. “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.”