Different etiological entities of liver cancer across populations: Implications from age-period-cohort analysis on incidence trends

Background: The incidence of liver cancer has shown different temporal trends across populations, while the underlying reasons remain unclear. Methods: We examined temporal trends in the incidence of liver cancer in Hong Kong, Sweden, and the United States since the 1970s through 2021 using joinpoint regression and age-period-cohort analysis. Results: The age-standardized incidence rate of liver cancer in Hong Kong steadily decreased (average annual percentage change [AAPC] -2.2%, 95% confidence interval [CI] -2.8% to -1.7% in men; AAPC -2.1%, 95%CI -3.1% to -1.1% in women) in 1983-2020. The rate in Sweden increased on average by 0.8% (95%CI 0.2% to 1.4%) per year in men and was stable in women (AAPC 0.2%, 95%CI -0.9% to 1.4%) in 1970-2021. The rate in the United States increased by 2.1% (95%CI 1.5% to 2.8%) per year in men and by 2.1% (95%CI 1.6% to 2.5%) in women in 1975-2020, but decreasing trends were noted in 2015-2020 (AAPC -6.6%, 95%CI -8.3% to -4.9% in men; AAPC -4.2%, 95%CI -7.5% to -0.5% in women). Stratified analysis by histological type showed such decrease in recent years was limited to hepatocellular carcinoma, rather than intrahepatic cholangiocarcinoma. We observed distinct changes in trends across age groups and different trends across birth cohorts. Conclusion: The incidence of liver cancer has decreased in Hong Kong but increased in Sweden and the United States since the 1980s, despite decreasing incidence in the United States since 2015. Such disparities may be explained by different etiology and implementation of preventive measures across populations.