Previous studies have not examined young adult cancer incidence trends in Taiwan, or comprehensively compared these trends at two nations with different population genetics, environmental exposures, and health care. Therefore, we compared the incidence rates and trends of the most common young adult cancers diagnosed at 20–39 years of age in Taiwan and the U.S.
Incidence rates from 2002 to 2016 were calculated from the Taiwan National Health Insurance Research Datasets and the U.S. Surveillance, Epidemiology, and End Results Program. For trend assessment, average annual percent change (AAPC) values were calculated from 15 years of data using Joinpoint Regression Program. We also obtained sex or age of diagnosis stratified estimates.
The age-standardized overall young adult cancer incidence rate significantly increased from 2002 to 2016 in both Taiwan (AAPC=1.1%, 95% CI: 0.8–1.5%) and the U.S. (AAPC=1.8%, 95% CI: 1.1–2.4%). Cancers with significantly decreasing trends in Taiwan included cancers of the nasopharynx, liver, and tongue, which were not among the most common young adult cancers in the U.S. Cancers with significantly increasing trends in both Taiwan and the U.S. included colorectal, thyroid, and female breast cancers. Lymphoma, ovarian cancer, and lung and bronchus cancer had significantly increasing trends in Taiwan but not in the U.S. Although cervical cancer had significantly decreasing trends in both nations among those 30–39 years of age, its trend was significantly increasing in Taiwan but decreasing in the U.S. among those 20–29 years of age.
The types of common young adult cancers as well as their incidence rates and trends differed in Taiwan and the U.S. Future studies should further understand the etiological factors driving these trends.
- • Common young adult cancer types, rates, and trends differed in Taiwan and the U.S.
- • Colorectal, thyroid, and breast cancers significantly increased in both nations.
- • Lymphoma, ovarian cancer, and lung cancer significantly increased only in Taiwan.
- • Cervical cancer diagnosed at age 20–29 years significantly increased only in Taiwan.
- • Nasopharynx, liver, and tongue cancers significantly decreased in Taiwan.
Cancers diagnosed in young adults 20–39 years of age have distinct topographical and biological characteristics compared with cancers in children or older adults . Young adults can have long remaining lifespans, and are often in school or starting a family and career, so receiving a cancer diagnosis can significantly affect quality of life and productivity. To our knowledge, no study has compared in detail the common young adult cancer incidence rates and trends by analyzing cancer registry data at two nations with different population genetics, environmental exposures, and health care, which will be informative for understanding the etiology of young adult cancers.
Young adult cancer temporal incidence trends have been studied in the U.S. and South Korea , but not in Taiwan, an island nation in East Asia with a national health insurance system populated by over 23 million people. Previous studies in Taiwan have only examined cancer incidence trends for infants , children and adolescents , or adults in general . The U.S. studies of young adult cancer examined cancers diagnosed at 20–49 years of age from 1999 to 2015 , and 15–39 years of age from 1973 to 2015 . The South Korean study of young adult cancer examined the age range of 15–39 years from 1993 to 2016 . Previous cancer incidence trend studies in Australia and France involving young adults only examined up to the age of 24 years . Although previous studies in Taiwan have found increasing incidence trends for all cancers combined , they have not examined the trends for young adult cancers diagnosed at 20–39 years of age. Furthermore, previous young adult cancer incidence trend studies in the U.S. have not performed trend analyses stratified by age of diagnosis . In this study, we compared the overall, sex-stratified, and age of diagnosis-stratified common young adult cancer incidence rates and trends from 2002 to 2016 in Taiwan and the U.S. by directly analyzing data from their cancer registries, to address the gaps in the previous literature and to understand the differences in young adult cancer incidence at these two geographically distant nations with distinct characteristics.