Cancer

International Childhood Cancer Day: Questions & Answers

How common are childhood cancers?

The term “childhood cancer” is most commonly used to designate cancers that arise in children before the age of 15 years. Childhood cancers are rare, representing between 0.5% and 4.6%* of all cancers. The overall incidence rates of childhood cancer vary between 50 and 200 per million* children across the world.

Which are the most frequent types of childhood cancers?

The pattern of cancers in childhood differs considerably from those among people of all other ages. In general, leukaemia constitutes about a third of all cancers in childhood. The other most common malignancies are lymphomas and tumours of the central nervous system. There are several tumour types that occur almost exclusively in children including neuroblastoma, nephroblastoma, medulloblastoma and retinoblastoma. Cancers of the breast, lung, colon or rectum, typically occurring in adults, are extremely rare in children.

What are the known risks for developing childhood cancer?

To date only a few definite risk factors for childhood cancers have been identified. These include ionising radiation and ingestion of the hormone diethylstilbestrol during pregnancy (a treatment no longer in use). A number of childhood cancers are also associated with genetic constitution, as suggested by the differences in incidence of childhood cancer between ethnically divergent populations. Individual susceptibility based on genetics may also play a role. Some studies have suggested that viruses such as Epstein-Barr, Hepatitis B, Human Herpes and HIV may also contribute to increased risk for some childhood cancers.

Are there geographical variations in the incidence of childhood cancer?

Cancer registries which record the incidence of cancer are not available in all low- and middle-income countries, as such it is difficult to have a comprehensive picture of childhood cancer around the world. Based on the information available, there appear to be wide variations in the incidence of childhood cancers such as leukaemia and tumours of the nervous system. While such cancers are rarely diagnosed, for example, in sub-Saharan Africa, populations in that region have higher incidence rates of lymphomas, in particular Burkitt lymphoma, than in other regions. This may result from greater exposure to viral infections.

Can childhood cancers be detected early?

Most childhood cancers initially present with non-specific signs and symptoms, which may lead to late detection. In high-income countries, because children are usually subjected to close parental and medical surveillance, cancers have a high chance of being detected early. In low-resourced countries, however, there are additional barriers to early detection, including poor to access health services and inadequate diagnostic facilities.

What are the chances of curing childhood cancer?

In high-income countries, approximately 80% of children with cancer survive five years or more after the diagnosis of cancer. These improving outcomes result in a growing population of long-term survivors who need follow-up treatment and care. The prognosis is much lower for children diagnosed with cancer in low- and middle-income countries. Factors explaining this include: the late diagnosis of cancer leading to lower levels of effective treatment; poorly equipped hospitals without the appropriate medicines and equipment; other diseases that children might have; and a lack of knowledge about cancer among primary health care providers. In addition, treatment is simply not affordable for many parents in low-resource settings who would be required to pay for the costs themselves.

Where can data on childhood cancer be found?

Data on cancer incidence are reflected in cancer registries, but there are fewer such registries in low- and middle-income countries than in high-income countries. The International Agency for Research on Cancer (IARC) through its Global Initiative for Cancer Registry Development (GICR http://gicr.iarc.fr/) is building national capacity for cancer registration in low- and middle-income countries.

* Reference: IARC World Cancer Report 2014 Lyon France
http://www.iarc.fr/en/publications/books/wcr/index.php

Prepared collaboratively by Eva Steliarova-Foucher (IARC) and Andreas Ullrich (WHO)

Produced in February 2015
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