Diverging global incidence trends of early-onset cancers: comparisons with incidence trends of later-onset cancers and mortality trends of early-onset cancers

BACKGROUND: The global increase in the incidence of early-onset cancers (defined as cancers diagnosed at 20-49 years old) is a serious public health problem. We investigated 1) whether the incidence trend of early-onset cancers differs from that of later-onset cancers and 2) whether both the incidence and mortality of early-onset cancers have increased concurrently. METHODS: We utilized age-standardized incidence and mortality rates for early-onset and later-onset cancers diagnosed between 2000 and 2017 from the Cancer Incidence in Five Continents and World Health Organization (WHO) mortality databases. The national obesity prevalence among adults aged 20-49 years was obtained from the National Clinical Database. Using joinpoint regression models, we calculated average annual percentage changes (AAPCs) for cancer incidence and mortality by cancer types and countries. We additionally conducted human development index (HDI)-stratified analyses and assessed the correlation between the obesity prevalence in younger populations and early-onset cancer incidence by country. To investigate the more recent trend of early-onset cancer mortality, we extended our mortality analysis after 2017 for cancer types and countries with statistically significant positive AAPCs in both incidence and mortality of early-onset cancers between 2000 and 2017. RESULTS: Our analysis showed that 10 early-onset cancer types (thyroid cancer, breast cancer, melanoma, uterine cancer, colorectal cancer, kidney cancer, cervical cancer, pancreatic cancer, multiple myeloma, Hodgkin lymphoma) in females and 7 early-onset cancer types (thyroid cancer, kidney cancer, testis cancer, prostate cancer, colorectal cancer, melanoma, leukemia) in males had statistically significant positive AAPCs in at least 10 countries. Among these, the following early-onset cancer types had significantly higher AAPCs than later-onset cancer types in females: colorectal cancer (6 countries; AAPC range: 1.8-3.8%), cervical cancer (6 countries; AAPC range: 1.2-3.3%), pancreatic cancer (5 countries; AAPC range: 2.3-13.0%), and multiple myeloma (5 countries; AAPC range: 3.1-9.8%); in males: prostate cancer (12 countries; AAPC range: 3.9-18.4%), colorectal cancer (8 countries; AAPC range: 1.8-3.2%), and kidney cancer (6 countries; AAPC range: 2.0-6.0%). We observed statistically significant positive AAPCs in both the incidence and mortality of the following early-onset cancer types: uterine cancer (5 countries) and colorectal cancer (3 countries in females and 5 countries in males). The steeper increases in early-onset cancers compared with later-onset cancers were mainly observed in the very high-HDI country group, including early-onset colorectal cancer (AAPC = 2.4%, 95% CI 2.1-2.6 in females; AAPC = 2.0%, 95% CI 1.7-2.4 in males) to later-onset colorectal cancer (AAPC = -0.1%, 95% CI -0.2 to 0 in females; AAPC = -0.2%, 95% CI -0.3 to 0 in males). We observed strong positive correlations between the increasing obesity prevalence and the rising incidence of early-onset obesity-related cancers in several countries, including Australia (7 cancer types), United Kingdom (7 cancer types), Canada (7 cancer types), Republic of Korea (7 cancer types), and USA (6 cancer types) in females and United Kingdom (7 cancer types), Canada (6 cancer types), Australia (5 cancer types), Sweden (5 cancer types), and Republic of Korea (4 cancer types) in males. Although we did not observe an apparent spike after 2017 in many countries, we observed continued increases in the mortality of certain cancer types, such as uterine cancer (Japan, Republic of Korea, United Kingdom, USA, and Ecuador) in females and colorectal cancer (Argentina, Canada, United Kingdom, and USA) in males. CONCLUSIONS: The increase in many early-onset cancer types was significantly higher than that of later-onset cancers, and the incidence and mortality of certain early-onset cancer types (such as colorectal cancer) increased simultaneously. Our study highlights global differences in cancer incidence and mortality trends of early-onset and later-onset cancers.