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Lung cancer is the most common cancer and the most common cause of cancer death in Hong Kong. Researchers from The Chinese University of Hong Kong’s (CUHK) Faculty of Medicine (CU Medicine) and the Association of Pacific Rim Universities (APRU) conducted a study to investigate the distribution, risk factors and epidemiological trends of this lethal disease. The results showed that the incidence and mortality of lung cancer were the highest in Eastern Asia, and were associated with the Human Development Index (HDI), Gross Domestic Product (GDP) and prevalence of smoking at a country level.

There was an overall increasing trend in females but a decreasing trend in males in lung cancer incidence and mortality over the past decade. The researchers suggested tobacco-related measures and early cancer detection for high-risk populations should be implemented to control the rising numbers. Details of the study have recently been published in the medical journal Chest.

Lung cancer is a global burden, accounting for one-fifth of all cancer mortality in the world

Lung cancer is a global burden. As its five-year survival rate is much lower than that of other major cancers, lung cancer accounted for around one-fifth of all cancer mortality in the world in 2020. To understand the most updated geographical distribution and to identify the high-risk population groups, the research team retrieved the lung cancer data from international databases such as the Global Cancer Observatory, WHO mortality database and WHO Global Health Observatory data repository for the current age-adjusted prevalence of smoking.

The researchers’ analysis showed that there was a wide variation in the disease burden of lung cancer, with the highest incidence and mortality in Eastern Asia. Detailed figures are as follows:

Higher incidence and mortality rates were also associated with a higher HDI, GDP and prevalence of smoking. This means that more developed countries and those with a higher prevalence of smoking tend to have higher lung cancer incidence and mortality.

The study shows lung cancer increasing globally among females but decreasing among males

There were significant sex differences in lung cancer incidence and mortality in the past decade, with many countries and regions showing declining trends in males and rising trends in females. Among these countries, Italy showed the highest decline (-3.5) in terms of average annual percentage change (AAPC¹) in the incidence for males, while Australia had the highest increase (1.7) in the incidence for females. For mortality, the Netherlands reported the greatest decrease (-3.3) in males, while Spain had the highest increase (4.0) in females.

Similar incidence patterns were found in those 50 years old or above, while those aged below 50 of both sexes had declining incidence trends.

According to the Hong Kong Cancer Registry, lung cancer became the city’s most common cancer in 2019, accounting for 27.1% of all cancer deaths. From 2010 to 2019, its incidence was increasing in females (1.2) of all ages while decreasing in males (-1.1). The incidence increase seemed more evident in the females aged less than 50 years (2.1) than older ones (1.1). Although its mortality decreases in both sexes, the decrease was less evident in females (-1.9) than males (-2.9).

Dr. HUANG Jun Jie, first-author of the study and Post-Doctoral Fellow from The Jockey Club School of Public Health and Primary Care at CU Medicine, stated, “The reasons for the age, sex and regional differences in the overall incidence and mortality trends of lung cancer were related to tobacco consumption. For example, there is a study showing that the smoking cessation rate was significantly higher in older males than females. But it is notable that second-hand smoke, indoor air pollution and exposure to chemicals play important roles in the variations too.”

Professor Martin Chi Sang WONG, the senior corresponding author of the study, from The Jockey Club School of Public Health and Primary Care at CU Medicine, suggested, “Evidence-based, tailored preventive strategies should be implemented by policy makers from different regions in order to control the increasing trends of lung cancer incidence and mortality in different populations. As an example, smoking cessation assistance and health education tailored for females or early cancer detection among this high-risk population may help reduce the burden of lung cancer. The findings from this global study may inform lung cancer control strategies in various countries.”

This paper is a collaboration with Professor Mellissa WITHERS, the Director of APRU Global Health Program; Keck School of Medicine, University of Southern California. APRU (https://apru.org/members/) was established in Los Angeles in 1997 by the presidents of UCLA, Berkeley, Caltech and the University of Southern California. It now has a membership of 61 leading research universities from around the Pacific Rim. CUHK is an important member of APRU, and Professor Martin Wong is currently co-chair of a Non-Communicable Diseases (NCD) Global Health Research Group in this network.

Study details can be found at: https://doi.org/10.1016/j.chest.2021.12.655

¹ AAPC is a measure of the overall changes in the cancer incidence or mortality for a specific period. For example, if the lung cancer incidence AAPC of a country is 5 for the past ten years, it means the lung cancer incidence in that country increased 5% on average each year over the 10-year period.