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