Childhood cancer incidences worldwide increased by about 13 per cent in the last decade, with annual cases reaching 140 per million children aged 014 years, according to a new WHO report.

Part of this increase may be due to better, or earlier, detection of these cancers, the report said.

Based on information collected globally on almost 300,000 cancer cases diagnosed in 2001-2010, the study showed that leukaemia is the most common cancer in children younger than 15 years, making up almost a third of childhood cancer cases.

Tumours of the central nervous system ranked second (20 per cent of cases), and lymphomas accounted for 12 per cent of cases, according to the study by the International Agency for Research on Cancer (IARC), part of the World Health Organisation (WHO).

In children younger than five years, a third of the cases were embryonal tumours, such as neuroblastoma, retinoblastoma, nephroblastoma, or hepatoblastoma.

The report also, for the first time, shows cancer occurrence in adolescents aged 1519 years. The annual incidence rate was 185 per million adolescents, based on records of about 100,000 cancer cases.

The most common cancers were lymphomas (23 per cent), followed by the cases classified as carcinomas and melanoma (21 per cent).

“Cancer is a significant cause of death in children and adolescents, in spite of its relatively rare occurrence before the age of 20 years,” said IARC Director Christopher Wild.

“This extensive new set of information on the pattern and incidence of cancer in young people is vital to raise awareness and to better understand and combat this neglected area of health early in life,” Wild said.

Data for the study was collected by 153 cancer registries in 62 countries, departments and territories, covering about 10 per cent of the world's population of children.

However, results reported are based on child population coverage of almost 100 per cent in North America and western Europe and of five per cent or less in Africa and Asia.

Incidence rates, which indicate the number of new cases per population at risk per year, are the first piece of information needed to start fighting this disease.

In low-resource settings, cancer may go undiagnosed, because awareness is lacking or diagnostic equipment is unavailable.

Also, social factors may explain the unexpectedly low rates reported particularly for infants or for girls in certain low-resource countries.

“This study provides the essential data we need to offer early detection, treatment, and care programmes and services for children with cancer,” said Tezer Kutluk, from the Union for International Cancer Control (UICC).

“It is very important that we improve global monitoring of cancer in children and address the gaps in surveillance data across regions,” said Kutluk.

The research was published in The Lancet Oncology journal.