Background
The lung is the most common site of cancer and has the highest worldwide cancer-related mortality. Advancements in lung cancer screening, new therapeutics, and guideline driven care over the past two decades have resulted in improvements in mortality. Few studies have reported on lung cancer trends in the 21st century. This study assessed the difference between lung cancer mortality by gender in the United States (US) and European Union (EU).

Methods
We utilized the World Health Organization (WHO) Mortality Database for European mortality data and Center for Disease Control (CDC) Wonder database for US mortality data. We extracted lung cancer mortality data from 2000 to 2017 based on ICD 10 system. Crude mortality rates were dichotomized by sex and reported by year. We computed Age Standardized Death Rates (ASDRs) per 100,000 population using the World Standard Population (and USA standard population for CDC mortality). We computed the ratio of male to female mortality over the observation period.

Results
We analyzed data from a total of 26 EU countries and the US, of which 6 countries had data till 2017, 12 till 2016, 7 till 2015 and 2 till 2014. All countries had greater mortality in men compared to women in all years. All countries had an overall decrease in the ratio of male-to-female mortality over the observation period. Specifically, in 2000, the median male-to-female mortality was 5.35 (IQR 3.65, 6.06) and for the most recent observation the median male-to-female mortality ratio was 2.26 (1.92, 4.05). The countries with the greatest current disparity in lung cancer mortality were Lithuania (5.51), Latvia (5.00), and Bulgaria (4.4). The countries with the smallest difference in mortality between sexes were Sweden (1.1), Denmark (1.13), United Kingdom (1.39). The median percentage change for all countries was – 44.45 (-50.44, - 30.56). The countries with the greatest percentage change were Spain (- 55.19), Belgium (-55.18), Cyprus (-53.64). The countries with the smallest percentage change were Bulgaria (-21.65), USA (-22.05), and Portugal (-25.46).

Conclusions
This study reports a decrease in the ratio of male-to-female mortality over the observation period across the EU and US. The greatest sex differences in mortality were in Eastern European countries and the smallest differences were in Northern Europe.

Legal entity responsible for the study
The authors.

Funding
Has not received any funding.