The risks of getting cancer are different for people with Down's syndrome, compared to the rest of the population.

There is one type of cancer which is definitely commoner in young people with Down's syndrome. This is a type of leukaemia called acute myeloid leukaemia (AML). The great majority of cases of AML in children with Down's syndrome develop before the age of 4 years old although occasionally older children and adolescents are affected. Overall somewhere between 1 in 50 to 1 in 100 children with Down's syndrome will get AML. Although AML is more common in children with Down's syndrome there is good evidence that they actually respond better to treatment than other children and are more likely to be cured.

For other types of leukaemia the frequency of acute lymphatic leukaemia (ALL) is similar in people with Down's syndrome to the rest of the population whereas both chronic myeloid leukaemia and chronic lymphatic leukaemia seem to be less common.

For other kinds of cancer it has been suggested that lymphomas and testicular cancer occur more often with Down's syndrome but the evidence for this is uncertain, so even if there is any increased risk it is very small.

The likelihood of developing other types of cancer does seem to be definitely reduced if you have Down's syndrome. This is most striking for breast cancer which is rare in women with Down's syndrome but affects more than 1 woman in 10 in the rest of the population.