Epidemiology of childhood hematologic cancers in Africa: A systematic review of the evidence

Abstract

Background: In developed economies, less than 1% of all cancers occur in children younger than 15 years. Less is known about the distribution of childhood cancers in Africa due to a lack of comprehensive data on pediatric oncology needs and burdens.

Methods: We searched EMBASE, Medline and Global Health to identify population- or hospital-based registry studies on childhood haematological cancers in Africa, with publication date set from January 1980 to December 2016. We applied a Bayesian network meta-analysis modelling approach on individual national or subnational estimates to arrive at a standardized estimate for Africa and African sub-regions.

Results: Our search identified 2717 studies, 35 of which met the inclusion criteria. Most studies were from the Southern and West African countries, and the majority (90%) of the cancer registries were population-based. Fifteen (43%) out of the 35 included studies were of high quality, while the remaining 20 (57%) included studies were of moderate quality. Most of the assessed studies (80%) were considered representative of their target/subnational population, with only 5 (14%) studies representative of their national population. From all sites, the pooled incidence of childhood leukemia in Africa was highest at 16.9 (95% CI: 14.1-19.7) per 1,000,000 child years (cy), with higher incidence in North Africa compared to sub-Saharan Africa (SSA). This was closely followed by non-Hodgkin lymphoma (NHL) at 16.8 (95% CI: 13.6-19.3) and Burkitts lymphoma (BL) at 16.8 (95% CI: 12.7-20.2) per 1,000,000 cy, with higher incidence rates of both cancer types significantly higher in SSA compared to North Africa. The overall pooled incidence of childhood Hodgkin lymphoma (HL) in Africa was the lowest at 15.0 (95% CI: 12.7-17.8) per 100,000 cy. Across all sub-regions, the incidence rates of the four cancer types were highest in East Africa, and consistently increased between 1980 and 2015.

Conclusion: Describing the epidemiology of childhood cancers remains difficult owing to few and limited capacities of cancer registration systems in Africa. Available evidence suggests an increasing incidence, with the East African region contributing highest to the burden of childhood hematological cancers on the continent. To provide evidence-based summaries on paediatric malignancies and guide appropriate response on the continent, there is need to re-organize existing registries and incorporate upcoming registries to comprehensively account for incidence, mortality, survival and relevant details on environmental, genetic and molecular characteristics of childhood cancers across different population groups.