Young adults aged 20 to 39 years represent a distinct group in terms of the type and rate of cancers diagnosed yearly, which differ from the types of cancer occurring either in older individual or in children and adolescents. Moreover, worldwide, the highest incidence of newly diagnosed cancer within this age group was observed in women.
“The burden of cancer among young adults has rarely been studied in depth,” Miranda Fidler, Section of Cancer Surveillance, International Agency for Research on Cancer in Lyon, France and colleagues wrote in a recent Lancet Oncology article. Their population-based study describes the scale and profile of cancer incidence and mortality worldwide among 20 to 39 year-old, highlighting the major patterns by age, sex, development level, and geographical region.
Young adult cancer was defined as cancer occurring between the ages of 20 and 39 years in individuals that have passed puberty and adolescence, but have not yet experienced the effects of hormonal decline, immune response deterioration, or organ dysfunction associated with chronic health conditions.
All cancer types included in the International Agency for Research on Cancer’s GLOBOCAN 2012 were assessed according to specific data estimates of the number of new cancer cases and cancer-associated deaths that occurred in 184 specific countries and described by global, and regional prevalence. All cancers occurring in young adults recorded in this database were extracted in four 5-year bands and included 27 major types defined by the International Classification of Disease, tenth revision.
This audit reported the number of new cancer cases and cancer-associated deaths overall and by sex, together with the corresponding age-standardised rates (ASR) per 100 000 people per year, and by the developmental status of the country. Countries were described according to developmental levels defined in the Human Development Index (HDI) as low, representing the least developed, medium, high, and very high or most developed. Developmental status was used as a composite indicator for socioeconomic development comprising life expectancy, education, and gross national income.
The cancers diagnosed most often globally in young adults were breast and cervical cancer
The investigators found that 975 396 new cancer cases (excluding non-melanoma skin cancer) and 358 392 cancer-associated deaths occurred among young adults globally in 2012, equating to an ASR of 43.3 new cancer cases per 100 000 people and 15.9 cancer-associated deaths per 100 000 people yearly.
The cancer burden within the young adult age group was disproportionally greater in women, who accounted for nearly twice the number of newly diagnosed cancer cases at 632 675 compared to 342 721 in men.
The most commonly occurring cancers among young women were breast and cervical cancer. The ASR for incidence of breast cancer was 17.0 per 100 000 people and the ASR for mortality due to breast cancer was 4.4 per 100 000 people per year. The ASR for the incidence of cervical cancer was 9.9 per 100 000 people and the ASR for mortality due to cervical cancer was 2.5 per 100 000 people per year. Other cancers frequently diagnosed in young women included thyroid cancer, with an incidence of 78 568 (8.1%), ASR 3.5 per 100 000 people, leukaemia at 49 293 (5.1%) new cases, ASR 2.2 per 100 000 people per year, and colorectal cancer with 41 117 (4.2%) newly diagnosed cases and ASR 1.8 per 100 000 people per year. Notably, thyroid cancer was 4-fold more common in women than in men, with an ASR of 5.7 per 100 000 women per year compared to 1.4 per 100 000 men per year.
Among young men, the most frequently diagnosed cancers were liver cancer, with an incidence of 31 767 (9.3%), ASR 2.8 per 100 000 people, testis 30 580 (8.9%) new cases, ASR 2.7 per 100 000 people per year, leukaemia 28 020 (8.2%) incidence, ASR 2.5 per 100 000 people, non-Hodgkin lymphoma 23 746 (6.9%), ASR 2.1 per 100 000 people per year, and colorectal cancer with 21 055 (6.1%) newly diagnosed cases and ASR 1.8 per 100 000 people per year.
Worldwide, the cancer types most prominent in young adults were female breast and cervical cancer, thyroid cancer, leukaemia, and colorectal cancer. In terms of yearly deaths due to cancer, female breast cancer, male liver cancer, leukaemia, and female cervical cancer were the main cancer types implicated.
The cancers diagnosed in young adults represent a distinct spectrum of disease
The spectrum of cancer types observed in young adults aged 20 to 39 years differed from the types diagnosed in both younger and older ages. Although some tumour types diagnosed in children and adolescents, such as leukaemia and cancers of the brain and CNS also commonly seen in young adults, epithelial tumours such as breast cancer, which ranked first for new cases and deaths overall, cervical cancer, which ranked second for new cases and fourth for deaths overall, and colorectal cancer, which ranked fifth for new cases and sixth for deaths overall were more frequently observed among young adults than in children or adolescents, but were diagnosed less frequently in young adults than in older age groups.
The profile of cancer incidence varied substantially when assessed by development level and geographical region, where the burden of infection-associated cancers such as HPV-associated cervical cancer or hepatitis-associated liver cancer, was greater in regions under transition.
Mortality demographics differ in regions with low socio-economic development
While cancer incidence was higher in very high-HDI regions compared with low-HDI regions, with ASR 64.5 versus 46.2 cancer cases per 100 000 people per year, respectively, the mortality burden was nearly 3-fold higher in low-HDI regions. The mortality burden reflected inferior outcomes in low-HDI countries, where the cancer-associated death ASR was 25.4 versus 9.2 per 100 000 people per year.
To the authors’ knowledge, this study is the first to explore the global burden of cancer among young adults, which was found to vary substantially according to sex, country development level, and geographical region.
Although the cancer burden is lower in this age group than that observed in older age groups, the societal and economic effects are great given the major effects of premature morbidity and mortality. Targeted surveillance and prevention especially for the cancer types found to be specific and higher in young adults could result in earlier diagnosis and more favourable outcomes.
This study discloses the barriers to improving cancer information and outcomes in young adults in low-income, countries, and suggests opportunities for improvement, including vaccination strategies, surveillance, early detection programmes, and improved curative treatment, which could reduce the cancer burden in this underserved age group.
No external funding was disclosed.
Fidler MM, Gupta S, Soerjomataram I, et al. Cancer incidence and mortality among young adults aged 20–39 years worldwide in 2012: a population-based study. Lancet Oncol; Published online 27 October 2017. http://dx.doi.org/10.1016/S1470-2045(17)30677-0