Incidence of childhood leukaemia

The number of new cases diagnosed each year increased steadily through the twentieth century.

The most common childhood cancer

Leukaemia is the most common childhood cancer, affecting up to 500 children every year in the UK.

About one third of all childhood cancers are leukaemias.

Brain and spinal tumours are the next most common cancers, accounting for just under a quarter of cases.

In 2003 (latest complete figures) there were 470 cases of leukaemia diagnosed in children in the UK (0-14 years of age; five year annual average is 466 cases). [Data from Office of National Statistics, Welsh Cancer Intelligence and Surveillance Unit, Information and Statistics Division – NHS in Scotland and Northern Ireland Cancer Registry.]

Increasing incidence

Incidence of childhood leukaemia appears to have increased steadily throughout the 20th century, as shown in the chart below.

Trends in childhood leukaemia incidence, survival and mortality, 0-14 years, England and Wales 1911-2000. Incidence and mortality rates per million for England and Wales, five-year relative survival rates (%) for children diagnosed in South-East England 1960-88 and in Great Britain 1993-97 (Coleman M and Shah A. 2004. Time trends in childhood leukaemia incidence. CHILDREN with LEUKAEMIA international conference, London).

National records of childhood leukaemia incidence were not kept before 1962 although mortality data were recorded from 1911. Until the 1960s, however, leukaemia in children was almost always fatal and so mortality rates are a reasonably accurate reflection of incidence rates.

A recent study of childhood cancer rates in Europe showed an average annual increase of 1.4% in childhood lymphoid leukaemia during 1970-1999 (1). The increasing incidence appears to be affecting mainly the under-five age group with incidence in older children remaining fairly static.

Under-fives now account for more than half of all cases of childhood leukaemia.

Boys are at higher risk than girls

Leukaemia is about 10% more common in boys than in girls. The reason for this difference between the sexes is not known.

The childhood peak

The incidence of childhood leukaemia varies with age.

Registrations of childhood acute lymphoblastic leukaemia in England (2003). Source: National Statistics, Series MB1, no 34.

The risk of acute lymphoblastic leukaemia (ALL) increases rapidly after birth, peaks around the third or fourth year of life and then declines. This peak first became evident in the 1930s and appears to be still increasing.

In contrast to the age incidence pattern of ALL, the highest risk of acute myeloid leukaemia (AML) is in children aged less than two years; the risk in children aged two to nine years is lower and it then rises through the adolescent years.

Registrations of childhood acute myeloid leukaemia in England (2003). Source: National Statistics, Series MB1, no 34.

Worldwide-incidence

The annual incidence rate of childhood leukaemia varies world-wide between 20 and 60 cases per million (2). The annual incidence rate in England and Wales in the period 1996–2000 was 46.1 per million.

More affluent countries generally tend to have higher incidence rates (with Switzerland, Finland and Italy having amongst the highest rates in the world) whilst less developed countries have some of the lowest rates. India and countries in Africa are amongst those with the lowest rates.

Incidence rates also vary by ethnicity within countries, as seen in the USA where the leukaemia incidence rates in white children (45.6 per million) are almost twice those in black children (27.8 per million) during the period 1986-95 (3). Incidence is high amongst Hispanics living in California (over 50 per million).

1. Steliarova-Foucher E, Still CA, Kaatsch P, Berrino F, Coeberg JWW, Lacour B, Parkin M. Geographical patterns and time trends of cancer incidence and survival among children and adolescents in Europe since the 1970s (the ACCIS project): an epidemiological study. Lancet 2004; 364: 2097-2105.
2. International Incidence of Childhood Cancer Vol II. IARC Scientific Publications No. 144. Parkin DM et al. Lyon International Agency for Research on Cancer, 1998.
3. Smith MA, Gloecker Ries LA, Gurney JG, Ross JA. Leukaemia. In: Ries LAG, Smith MA, Gurney JG, Linet M, Tamra T, Young JL et al. eds. Cancer incidence and survival among children and adolescents:United States SEER Program 1975-1995. NIH Pub No 99-4649 Bethesda, Maryland: National Cancer Institute, SEER Program, 1999.