The toll of childhood cancer

While the number of new cancer cases in children and adolescents (aged 0-19 years) is relatively low at around 416,500 globally in 2017, treatment-related ill-health and disability and fatal cancer are estimated to cause around 11.5 million years of healthy life lost globally every year, according to the first Global Burden of Disease Study (GBD) to assess childhood and adolescent cancer burden in 195 countries in 2017, published in The Lancet Oncology journal.

Children in the poorest countries face a disproportionately high cancer burden — contributing over 82% of the global childhood cancer burden — equivalent to almost 9.5 million years of healthy life lost in 2017. Most (97%) of this global burden is related to premature death, with around 3% due to impaired quality of life.

The study estimates the number of years of healthy life that children and adolescents with cancer have lost due to illness, disability, and premature death — a measurement known as disability-adjusted life years (DALYs). One DALY is equivalent to one year of healthy life lost.

Children with cancer who live in high-income countries tend to have good survival, with around 80% surviving 5 years after diagnosis. But these improvements have not translated to most low- and middle-income countries (LMICs), where survival is approximately 35-40%, but some estimates suggest it could be as low as 20%. Around 90% of children at risk of developing cancer live in LMICs.

The study reveals striking inequities in childhood cancer burden between high and low socio-demographic Index (SDI) countries. High and high-middle SDI countries accounted for about 35% (147,300) of new cases of childhood cancer in 2017, but only 18% of DALYs (around 2 million years of healthy life lost), whereas low-middle and low SDI countries with 38% of global incidence (159,600 new cases) accounted for 60% of DALYs (almost 7 million years of healthy life lost).

Moreover, the research finds that childhood cancers are a major cause of global disease burden compared with both adult cancers and other childhood diseases. In 2017, childhood cancers were the sixth leading cause of years of healthy life lost out of all cancers globally (11.5 million), only lower than the burden from adult cancers of the lung (41 million), liver (21 million), stomach (19 million), colon (19 million), and breast (18 million). In low and middle SDI countries, childhood cancers were the leading cause of DALYs, higher than the burden attributable to any single adult cancer type.

The study puts the annual toll of childhood cancer at over 11.5 million years of healthy life lost in 2017. This compares with around 37 million years of healthy life lost globally due to malaria, and 7.6 million from tuberculosis. In 2017, childhood cancer was among the top four biggest contributors to the burden of general diseases of childhood in middle and high-middle SDI countries, ranking higher than malaria and HIV/AIDS.

Cancers of the blood (leukaemias) were the main contributors to overall DALYs, accounting for 34% of the total childhood cancer burden worldwide, followed by brain and nervous system cancers (18%). In 2017, the proportion of both leukaemia and brain cancer burden differed by almost 3 times between regions. The proportional burden of leukaemias was highest in central and Andean Latin America (49% of all childhood cancers) and the greatest absolute burden was in south Asia (954,000 DALYs).

The authors highlight the fact that mechanisms for addressing cancer burden in adults, which focus on risk-reduction strategies and screening interventions, are not as relevant to childhood cancers given that childhood cancers generally progress rapidly, are not amenable to screening programmes which aim to identify pre-cancerous growths, and are fatal without swift diagnosis and treatment. This emphasises the crucial role early diagnosis and treatment will play in order to reduce the global burden of childhood cancer.