Cancer incidence and mortality among young adults aged 20-39 years worldwide in 2012: a population-based study.

BACKGROUND: To date, the burden of cancer among young adults has rarely been studied in depth. Our aim was to describe the scale and profile of cancer incidence and mortality worldwide among 20-39 year-olds, highlighting major patterns by age, sex, development level, and geographical region.

METHODS: We did a population-based study to quantify the burden of young adult cancers worldwide. We defined young adult cancers as those occurring between the ages of 20 and 39 years because these individuals will have passed puberty and adolescence, but not yet experienced the effects of hormonal decline, immune response deterioration, or organ dysfunction associated with chronic health conditions. Global, regional, and country-specific (n=184) data estimates of the number of new cancer cases and cancer-associated deaths that occurred in 2012 among young adults were extracted in four 5-year bands from the International Agency for Research on Cancer's GLOBOCAN 2012 for all cancers combined and for 27 major types as defined by the International Classification of Disease, tenth revision. We report the number of new cancer cases and cancer-associated deaths overall and by sex alongside corresponding age-standardised rates (ASR) per 100 000 people per year. We also present results using four levels of the Human Development Index (HDI; low [least developed], medium, high, and very high [most developed]), which is a composite indicator for socioeconomic development comprising life expectancy, education, and gross national income.

FINDINGS: 975 396 new cancer cases and 358 392 cancer-associated deaths occurred among young adults worldwide in 2012, which equated to an ASR of 43·3 new cancer cases per 100 000 people per year and 15·9 cancer-associated deaths per 100 000 people per year. The burden was disproportionally greater among women and the most common cancer types overall in terms of new cases were female breast cancer, cervical cancer, thyroid cancer, leukaemia, and colorectal cancer; in terms of deaths, female breast cancer, liver cancer, leukaemia, and cervical cancer were the main contributors. When assessed by development level and geographical region, the cancer profile varied substantially; generally, the burden of infection-associated cancers was greater in regions under transition. Cancer incidence was elevated in very high-HDI regions compared with low-HDI regions (ASR 64·5 vs 46·2 cancer cases per 100 000 people per year); however, the mortality burden was 3 times higher in low-HDI regions (ASR 25·4 vs 9·2 cancer-associated deaths per 100 000 people per year), reflecting differences in cancer profiles and inferior outcomes.

INTERPRETATION: The global cancer burden among 20-39 year-olds differs from that seen in younger or older ages and varies substantially by age, sex, development level, and geographical region. Although the cancer burden is lower in this age group than that observed in older ages, the societal and economic effects remain great given the major effects of premature morbidity and mortality. Targeted surveillance, prevention, and treatment are needed to reduce the cancer burden in this underserved age group.

FUNDING: International Agency for Research on Cancer (IARC) and European Commission's FP-7 Marie Curie Actions-People-COFUND.