A mobile health clinic in Kathmandu.Credit: Jonas Gratzer/LightRocket via Getty

Almost half of childhood cancer cases worldwide go undiagnosed, according to an analysis.

Using data from the World Health Organization (WHO), researchers estimate that in 2015, 397,000 children under 15 developed cancer globally — and that 43% of those cases went undiagnosed.

The figures are much higher than those from official cancer registries, say the scientists, meaning that tens of thousands of children each year go without treatment, and potentially die from the disease without knowing they have it.

Previous estimates have suggested that 200,000 children worldwide are diagnosed with cancer each year.

The true number of cancer cases in many countries is hard to pin down, because most do not record such data. In West Africa, for example, only Mali and Cameroon have publicly available registry data on childhood cancers. And in the countries that do have registries, many cases might be missed, and therefore go undocumented.

“Because a lot of children don’t have access to primary care, they don't have access to cancer specialists — they don’t end up getting diagnosed,” says Zachary Ward, a health-policy researcher at Harvard University in Cambridge, Massachusetts, and co-author of the modelling paper, published on 26 February in The Lancet Oncology1.

Source: Z. J. Ward et al. Lancet Oncol. http://doi.org/c3gr (2019)

Identifying the gap

To get more accurate numbers, Ward and his colleagues developed a model that used registry data to estimate how many children with cancer were never diagnosed. The model used WHO data on people access to pregnancy care and vaccinations, as well as the number of children treated for pneumonia and diarrhoea, which they used as measures of barriers to health care that could result in missed cancer diagnoses.

The researchers also input demographic data on income and on the proportion of the population living in urban areas to account for differing access to primary care. They compared the model’s predictions with real data on childhood cancer from national registries and adjusted it on the basis of the results.

They revealed a vast disparity in the number of undiagnosed cases across the world. In western Europe and North America, for example, only 3% of cases are missed, whereas in south Asia and West Africa, that figure rises to 49% and 57%, respectively (see ‘Missing cancer diagnoses’).

Ward’s team also predicted that, between 2015 and 2030, 6.7 million children will develop cancer worldwide. If health-care systems don’t improve, around 2.9 million of those cases will slip through the cracks.

Global burden

The estimates are a welcome step towards determining the global childhood-cancer burden, says Peter Kaatsch, director of the German Childhood Cancer Registry in Mainz.

Ward and his colleagues are now working to estimate the overall survival rates of childhood cancers using a similar model. He hopes the results will influence policymakers.

“I hope this at least starts the conversation and convinces them of the need to invest more in health system strengthening, and also in cancer registration systems so that we can track progress,” he says.