Introduction

Lung cancer has been consistently the leading cause of cancer incidence and mortality worldwide over several decades. In 2018, there were over two million new lung cancer cases and 1.7 million deaths, representing 14% of the total number of new cancer cases estimated globally, and 20% of the cancer deaths.¹ More than half of the global burden of incidence and mortality occurs in low and middle income countries (LMIC). Prognosis following a lung cancer diagnosis remains poor; even in high-resource settings, with five-year relative survival ranging from 32.9% in Japan to 13.3% in the United Kingdom over the diagnostic period 2010-2014.²

The most important cause of lung cancer is tobacco smoking, with tobacco classified as carcinogenic in humans (Group 1A).³ The geographic pattern worldwide thus depends on the past tobacco smoking histories of the underlying populations, given an average latency period of more than two decades.⁴ The establishment of the World Health Organization Framework Convention on Tobacco Control (FCTC) and the implementation of its policy package (MPOWER) has contributed to a reduction in smoking prevalence and subsequently in rates of lung cancer and of many other tobacco-related diseases in many countries; nevertheless, with an estimated global population of 1.1 billion people (aged≥15 years) smoking tobacco in 2016, strengthening the implementation of the FCTC in all countries remains a key contributory action to the goal of reducing smoking prevalence by about a third by 2025.⁵

Comparable incidence statistics at the global level are important metrics for evaluating the lung cancer burden in different populations, revealing distinct patterns that may lead to more targeted tobacco control interventions. We provide here an exposition of the most recent lung cancer incidence and mortality patterns using national estimates for 2018 according to world region from Globocan, as well as observed lung cancer incidence trends using the recorded data in Cancer Incidence in Five Continents (CI5). To aid interpretation, we further examine recent smoking prevalence figures in selected countries.

Results

Estimated incidence, mortality and cumulative risk 2018

Table I shows the estimated number of lung cancer cases in 2018 alongside the age-standardized rates (per 100 000) and cumulative risk of incidence and mortality, by world region and sex. Incidence rates varied ten-fold across regions, ranging from 3.4 in Eastern Africa to 49.3 in Eastern Europe. Marked variations were also seen between countries and sub-regions within continents, particularly in Africa (up to a six-fold variation), the Americas and Asia. Among females, rates were consistently lower than those observed in males, ranging from 1.2 in Western Africa to 30.7 in North America. The highest M:F ratios of around 5.0 were seen in Northern Africa and Western Asia, while the lowest M:F ratio of 1.2 were observed in Australia and New Zealand. The mortality rates and the corresponding M:F ratios showed a similar pattern as described for incidence.

Table I Estimated number of lung cancer cases, age-standardized (per 100 000 inhabitants) incidence and mortality rates (ASR) and cumulative risk, worldwide, in males and females, 2018 

		Incidence														Mortality
		Male						Female						M:F		Male						Female						M:F
		Cases		ASR		Cumulative risk		Cases		ASR		Cumulative risk				Cases		ASR		Cumulative risk		Cases		ASR		Cumulative risk
World		1 368 524		31.5		3.8		725 352		14.6		1.77		2.1		1 184 947		27.1		3.19		576 060		11.2		1.32		2.4
Africa
Eastern Africa		3 296		3.4		0.4		2 595		2.2		0.2		1.5		3 230		3.4		0.4		2 503		2.2		0.26		1.5
Middle Africa		1 285		3.8		0.4		975		2.3		0.2		1.7		1 240		3.6		0.4		911		2.2		0.26		1.6
Northern Africa		16 008		16.9		2.1		3 529		3.4		0.4		5.0		15 655		16.6		2.02		3 183		3.1		0.36		5.4
Southern Africa		5 634		26.0		3.0		2 782		8.9		1.0		2.9		5 348		25.0		2.92		2 597		8.3		0.96		3.0
Western Africa		2 087		2.4		0.2		1 162		1.2		0.1		2.0		2 058		2.4		0.26		1 023		1.1		0.12		2.2
America and Caribbean
Caribbean		6 540		23.5		2.8		4 466		14.2		1.7		1.7		5 866		20.8		2.49		3 609		11.2		1.36		1.9
Central America		5 962		7.2		0.8		4 300		4.5		0.5		1.6		5 368		6.4		0.74		3 619		3.7		0.43		1.7
South America		39 255		16.8		1.9		29 249		10.2		1.2		1.6		36 824		15.7		1.86		26 098		9.0		1.08		1.7
Northern America		133 950		39.1		4.7		118 796		30.7		3.8		1.3		91 957		25.8		3.02		81 321		19.4		2.29		1.3
Asia
Eastern Asia		633 284		47.2		5.6		316 731		21.9		2.6		2.2		557 985		41.1		4.74		257 650		17.1		1.99		2.4
South-Eastern Asia		78 453		26.3		3.0		34 729		9.6		1.1		2.7		70 504		23.8		2.82		30 227		8.4		0.98		2.8
South Central Asia		80 415		9.4		1.1		30 627		3.4		0.4		2.8		74 991		8.8		1.06		28 871		3.2		0.38		2.7
Western Asia		41 309		38.8		4.7		9 481		7.8		0.9		5.0		39 773		37.6		4.64		8 861		7.3		0.85		5.2
Europe
Eastern Europe		109 928		49.3		6.2		39 155		11.9		1.5		4.1		99 266		44.2		5.67		32 093		9.4		1.2		4.7
Northern Europe		39 265		34.0		4.0		35 106		26.9		3.3		1.3		30 144		25.1		2.88		25 571		18.1		2.18		1.4
Southern Europe		72 411		43.1		5.3		28 518		15.7		1.9		2.7		63 933		36.1		4.36		22 700		11.5		1.39		3.1
Western Europe		90 239		43.3		5.3		55 417		25.7		3.2		1.7		74 003		33.5		4.04		40 233		17.0		2.11		2.0
Oceania
Australia/New Zealand		8 345		28.4		3.2		7 239		24.0		2.96		1.2		6 026		20.0		2.3		4 547		14.3		1.73		1.4

Figures 1 A and 2A depict the national lung cancer incidence variations in males and females, respectively. The highest incidence rates were observed in Northern and Western European countries, in both sexes, while incidence rates were low in African countries. In the Americas, elevated incidence rates were observed in Uruguay and Cuba.

Figure 1  A) Estimated lung cancer incidence rates (ASR per 100 000) among males in 2018. B) Age-standardized tobacco smoking prevalence (%) among males 15 years and older in 2015 

Figure 2 A) Estimated lung cancer incidence rates (ASR per 100 000) among females in 2018. B) Age-standardized tobacco smoking prevalence (%) among females 15 years and older. 

Observed incidence circa 2008-2012

Lung cancer ASR circa 2008-2012 are presented by sex and region in figure 3. Overall, they varied markedly: among males, the highest incidence rates were observed in Portugal (ASR of 69.8), Turkey (69.3) and among US blacks (57.1), while in females, rates were highest in Denmark (36.8), and the Netherlands (29.5). The rates in Eastern European countries tended to be less variable in men, ranging from 46.6 in Ukraine to 60.9 in the Russian Federation. In Asia, male incidence rates were quite similar in China, Republic of Korea and Japan (ASR of 45.9, 45.8 and 44.9, respectively), while in the Americas and the Caribbean, elevated incidence rates among males were found in Uruguay (46.4) and the US (46.3). Generally, higher incidence rates were observed in countries classified as very high-income countries.

Figure 3 Observed age-standardized incidence rates (ASR) of lung cancer, in males and females, circa 2008-2012 

Temporal patterns 1980-2012

The trends in lung cancer incidence rates in selected countries 1980-2012 are plotted in figure 4. The majority of the countries exhibited stable or decreasing incidence rates among males, but increasing rates among females. In South America and the Caribbean, incidence rates increased among females in Ecuador and Brazil, while in Colombia and Costa Rica, rates were stable or in recent decline. North America and Oceania conveyed similar patterns, with decreasing rates in males and female rates either increasing or stabilizing. In Asia, incidence rates in Thailand and Philippines decreased over the study period in both males and females; while, in contrast, rising rates were seen in Japan, Republic of Korea and India in women. Among most Western European countries (Austria, Denmark, France, Germany, Switzerland and Netherlands), incidence rates among males were either flat or in decline, although female rates were increasing. A not dissimilar pattern was observed in Eastern Europe, particularly in Poland and Slovakia, and in Northern Europe, including Denmark.

^*National registry

Source: Cancer Incidence in Five Continents

Figure 4 Trend in observed lung cancer incidence in selected countries, among males and females, from 1980 to 2012. (continues…) 

Discussion

We present here the most recent estimates of lung cancer incidence and mortality worldwide, in 185 countries alongside recorded incidence data in 62 countries coupled with recent figures on tobacco smoking prevalence (%) among males and females 15 years and older. Overall, with two new million cases each year, lung cancer still represents the most important cancer worldwide, with an elevated incidence and mortality burden among males, relative to females. We observed significant variations in rates between and within regions worldwide, with Europe, Asia and North America observed to have the highest incidence rates worldwide, and sub-Saharan Africa, the lowest. Where temporal data were available, the lung cancer incidence trends varied considerably in their direction and magnitude; the most common pattern found among men was stable or decreasing trends, while increasing trends were predominant among women.

Current geographic patterns in lung cancer incidence mainly reflect recent and past exposure to tobacco. Tobacco smoking (both active and passive) is the main risk factor for lung cancer. The tobacco epidemic began among men at the beginning of the 19^th century in several high income countries, and developed in women one or more decades later.¹³ In our results, geographic variation in lung cancer between and within regions appears to correlate with current tobacco prevalence. Although recent incidence rates reflect the duration and intensity of tobacco smoking more accurately than 20 years ago.

Overall the current prevalence of tobacco use in the Americas is lower relative to Europe. In South America, the higher lung cancer incidence rates observed in Uruguay and Argentina, are consistent with the higher tobacco prevalence in both countries, as reported previously.^14,15 In the US, the declining rates in both sexes, first observed in males in the 1990s and in females in the 2000s is driven by the decreasing tobacco prevalence reported by Thun and colleagues,¹³ with an approximate 20 year lag between the peaks of smoking prevalence and lung cancer mortality rates. In Central and South America, the tobacco epidemic was initiated years later; Costa Rica and Colombia have seen decreasing incidence rates by 2000 and 1990 respectively, while rates in Ecuador have stabilized in men.

The burden of lung cancer in Asia is of particular concern. In many Asian countries, the prevalence of tobacco is high (at least relative to the US), although some declines in incidence rates have been observed from the mid-1980s in China (Harbin, Jiashan, Shangai, and Zhongshan), and the Philippines. Our results indicate a 10-fold difference between Asian countries, with the highest incidence observed in Turkey, China, the Republic of Korea and Japan. Although the prevalence of tobacco use among women in China and Republic of Korea tends to be considerably lower than in the US (less than 5% in 2015 in China and Republic of Korea versus 15% in the US), recent incidence rates were higher in Asia than in several European countries. This fact may be related to higher levels of indoor and outdoor pollution, an important risk factor for lung cancer in non-smokers.¹⁶ In Japan, we observed a plateau in incidence rates at the end of the 1980s, with a stabilization and slight decline by the early-1990s. As Japanese males started their smoking careers later than Northern American males,¹⁷ lung cancer incidence rates are presently lower, despite a higher prevalence of tobacco smoking. A declining prevalence of tobacco has been observed in the Japanese population in the 2000s (data not shown), with a slight increase in rates observed in females and a plateau in males.

The lung cancer epidemic has had an enormous impact on public health in European countries.¹⁸ As an example, the incidence rates in Portugal are the highest of the continent in men and 10-fold higher than in women, with further increases expected in women. Elsewhere the grounds for optimism, given declining incidence rates among men in Italy, United Kingdom, Denmark and Netherland, are countered in most European countries by the more recent tobacco epidemic in women, that is contributing to the rising incidence in this group, in both younger and older generations.¹⁸ Assessing these in the context of recent tobacco trends, the prevalence of current smoking in France for example, historically high in men, has declined progressively up until 2000 and remained relatively stable thereafter, while in women it has uniformly increased over the same period.¹⁹ Somewhat more encouraging are the declines in tobacco prevalence observed in women reported in several countries, suggesting that lung cancer rates will reach a plateau in future years and decline thereafter. Reliable tobacco prevalence data using comparable surveys is needed to assess this, and over the last decade substantial progress has been made in implementing the FCTC at the national level to enable best-practice policies that are adopted to protect millions of lives.

Robust national tobacco control policies are critical in curbing the global tobacco epidemic. In 2013, the WHO Global Action Plan for the prevention and control of noncommunicable diseases (NCDs) 2013-2020 called for governments to reduce the current burden of tobacco by about one-third by 2025, posing challenges to the assessment of long-term prevalence and implementation of MPOWER measures. MPOWER measures were established in 2008 to ensure cost-effective interventions that can lead to marked reductions in tobacco use.²⁰ In addition, monitoring tobacco use and prevention policies using standard methodology are being made possible through global surveys, including the Global Adult Tobacco Survey (GATS) and the Global Youth Tobacco Survey (GYTS). These have shown the inverse relationship between tobacco price and prevalence;²¹ raising taxes on tobacco is one of the most effective policies to reduce tobacco consumption.²² Increasing the price of tobacco through tax hikes discourage the young to commence smoking and supports the cessation in smokers; there is no safe level of tobacco consumption and the promotion of a smoke-free environment is an effective way to protect people, in particular from exposure to second-hand smoke.

The interpretation of the global pattern of lung cancer requires considerable caution, given its broad and complex relation with past tobacco consumption. It is also important to note that incidence data are derived from subnational cancer registries in some countries and they may not completely represent the national scale and profile. In addition, Thailand and United Kingdom present an artefact in rates around the 1990s, probable driven by changes in coding practices during the period.

In summary, this study has sought to report the most recent global figures on lung cancer based on high quality population-based cancer registries and tobacco prevalence data at the global, regional and national levels. We highlight the marked disparities in incidence between and within regions; the higher lung cancer incidence rates in parts of South America and Asia are important markers of the current tobacco epidemic and warrant further study to better understand the role of tobacco control prevention. Efforts should be made to improve the quality and the availability of tobacco prevalence information over time to permit more informative research based on international comparable statistics. The continuing rise in lung cancer among women in many countries further reinforces the need for the targeted implementation of smoking cessation policies to curb the tobacco epidemic and save millions of lives.