world cancer report - iarc

LEUKAEMIA
SUMMARY
> Leukaemia is the eleventh most common
cancer worldwide with more than
250,000 new cases each year. It typically
results from malignant transformation
of white blood cells or their precursors.
Subtypes are identified on the basis of
the cell of origin (lymphocytic or
myeloid, etc.) and clinical course (acute
or chronic).
> The etiology of leukaemia is largely
unknown, although a small proportion of
cases is attributable to treatment with
anticancer drugs or exposure to ionizing
radiation. The genetic characteristics of
many leukaemias have been elucidated.
> Treatment of acute leukaemia has made
muchg progress and helped to establish
general principles of cancer chemotherapy
and management.
> Survival varies greatly according to type,
with acute lymphoblastic leukaemia
patients having a five-year survival rate
of up to 70%, whilst for those with acute
myeloid leukaemia it is only 20-30%.
Definition
Leukaemias involve clonal, neoplastic proliferation
of immature cells, or blasts, of
the haematopoietic system. Principal subtypes
are identified on the basis of malignancy
involving either lymphoid (B-cells
and T-cells) or myeloid (i.e. granulocytic,
erythroid and megakaryocytic) cells, and
upon whether disease is acute or chronic
in onset [1].
Epidemiology
Leukaemias comprise about 3% of all
incident cancers worldwide, with about
257,000 new cases occurring annually.
Incidence rates for all types taken together
vary from about 1 to 12 per 100,000 population.
A relatively high incidence is evident
242 Human cancers by organ site
< 2.4
< 3.2
Fig. 5.108 Global incidence of leukaemia in women.
in the USA, Canada, Western Europe,
Australia and New Zealand, whilst rates are
generally low in most African and Asian
countries with rates less than half those in
the former group (Fig. 5.108). The trends in
overall incidence of leukaemia have generally
been stable or slowly increasing.
However, a substantial reduction in death
rates from leukaemias, particularly in childhood,
have been observed since the 1960s,
thanks to advances in treatment and consequent
improvement in survival.
Leukaemia has a peak in incidence in the
first four years of life, which is predominantly
due to acute lymphoblastic leukaemia
(ALL), the most common paediatric
malignancy, accounting for nearly 25% of
all such disease. After infancy, there is a
steep decline in rates of leukaemia with
age, lowest incidence being at age 15 to
25, after which there is an exponential
rise up to age 85 (Fig. 5.110). The frequency
of leukaemia per 100,000 individuals at
risk at age 85 is more than 300 times that
for those in the second decade of life.
The overall incidence of acute
leukaemia is 4 cases per 100,000 popu-
< 4.3
< 5.4
Age-standardized incidence/100,000 population
< 10.2
lation, the usual form of the disease in
adults being acute myeloid leukaemia
(AML) accounting for 70% of all cases.
The more differentiated, or chronic
forms of leukaemia, are predominantly
adult diseases, rarely occurring below
the age of 30, then increasing progressively
in incidence with age. Chronic
myelogenous leukaemia (CML) accounts
for 15-20% of all cases of leukaemia,
with a worldwide incidence of 1-1.5
cases per 100,000 population. For
patients over 50, chronic lymphocytic
leukaemia (CLL) is the dominant type of
leukaemia. All types of leukaemia combined
cause some 195,000 deaths
worldwide.
Etiology
The cause of most leukaemias is not
known. A range of risk factors has been
predominantly, although not exclusively,
associated with particular leukaemia subtypes.
Ionizing radiation (nuclear bombs,
medical procedures, [e.g. 2, 3]) and occupational
exposure to benzene are
associated with acute myeloid leukaemia.