Acute Leukemias - Republican Scientific Medical Library

80 Chapter 5 · Acute Lymphoblastic Leukemia: Epidemiology and Etiology
Fig. 5.1. Survival rates for childhood ALL. Five-year relative survival
rates for ALL and AML: End Results Group National Cancer Institute
Surveillance, Epidemiology and End Results Program, 1996. Squares:
ALL; circles: AML represent defined time periods. The “best fit” curve
was drawn by the author (from Kersey [54]).
5.2.3 Mortality
ALL represents less than 1.1% of total US cancer related
deaths and 28.9% of all leukemia deaths. In US children,
however, ALL represents almost 16% of total cancer
mortality and 50% of all leukemia deaths. Total leukemia
mortality rates in whites of both sexes decreased
from the 1980s through 2002. In blacks of both sexes,
however, total leukemia mortality rates increased after
1975, peaking in 1983 among females and in 1991 among
males, then decreasing through 2002. For all children
considered together, the mortality rates both for total
leukemia and for ALL declined from 1975 to 2002, but
the rate of decrease was greater in the 1990s [117].
5.2.4 Sex Differences
Incidence rates for total leukemia, and to a lesser extent
for ALL, are higher among males than among females,
and this gender difference is considerably more pronounced
among whites (70% more leukemia in males
and 60% more ALL in males) than among blacks
(30% and 15%, respectively). In children, the incidence
rates for all leukemias, and for ALL, are slightly higher
in males than in females, up to about a 30% excess [77].
Similar patterns are seen in the mortality data for all
leukemias, but for ALL male rates show an even greater
excess [117].
5.2.5 Race Differences
Overall differences in incidence and mortality rates by
race are also noteworthy. In the USA, for leukemia, for
males, females, and all combined, whites have higher incidence
rates than blacks (30–40% excess), and this
same pattern is seen even more strongly for ALL (85–
215% excess). A similar pattern is seen for mortality
[117].
In children, SEER summaries provide tabulations of
race-specific data only for all cancers [117]. For those
data, whites have about a 45–55% excess in incidence
rates, depending on gender, and similarly for mortality
rates, whites have a 5–10% excess depending on gender.
Other studies suggest that the rate of ALL in white children
is double that in black children in the USA [43, 77].
5.2.6 Age Differences
Leukemia incidence increases from birth through age 3,
then decreases until about age 50, when rates begin to
increase slowly. ALL incidence rates increase more dramatically
from birth to age 3 (up to more than 9 cases
per 100 000 per year), drop off to lower levels until
about age 50 (less than 1 per 100 000 per year), and then
increase slightly, but never approach the rates observed
between ages 1 and 14 (Fig. 5.2). The peak incidence period
is from age 2–5 [145] with a smaller, secondary peak
after age 60 (Fig. 5.3). It is interesting to note that the
age 2–5 peak in ALL was noted first in Western countries
between 1920 and 1945, thereafter in Japan and
China, and the incidence rate in affluent countries continues
to increase at a rate of about 1% per year [38].
Understanding the mechanism of this unexplained difference
between Western, affluent, developed countries
and those in the developing world might help unlock
the etiologic secret of what causes the leukemias and
ALL.
5.2.7 Parental and Birth Characteristics
Researchers have noted a variety of patterns among parental
and birth characteristics of leukemia and ALL
cases. For example, first-born babies have a higher risk
of ALL, as do high-birth-weight babies [124], babies
whose mothers are over 35 years of age, and mothers
who have had a prior fetal loss [120]. Maternal cigarette