world cancer report - iarc

BREAST CANCER
SUMMARY
> Breast cancer is the most common
malignancy affecting women, with more
than one million cases occurring worldwide
annually. Affluent societies carry
the greatest risk, with incidence rates of
>80 per100,000 population per year.
> The worldwide breast cancer epidemic
has many etiological factors, including
reproductive history (early menarche,
late or no pregnancy), and Western
lifestyle (high caloric diet, lack of physical
activity).
>In some regions, including North
America, Western Europe and Australia,
breast cancer mortality rates have started
to decline, mainly due to improvements
in early detection and treatment
(chemotherapy and tamoxifen). Fiveyear
survival rates are higher than 70%
in most developed countries.
> Breast cancer screening trials of mammography
have shown that mortality
can be reduced by up to 30%. However,
there is limited evidence that this can be
achieved in population-based countrywide
screening programmes.
Definition
Breast cancer generally refers to a malignancy
in women that arises from the terminal
ductal-lobular units of epithelial tissue,
which in the mature breast represent
10% of the total volume.
Epidemiology
Latest estimates suggest that more than
1,050,000 new breast cancer cases occur
worldwide annually, with nearly 580,000
cases occurring in developed countries and
the remainder in developing countries [1].
Thus breast cancer now ranks first among
cancers affecting women throughout the
world and its marked impact is not restricted
to Western industrialized societies (Fig. 5.12).
188 Human cancers by organ site
< 19.3
< 26.1
Fig. 5.12 The global burden of breast cancer in women; incidence is high in developed countries such as
the USA, UK and Australia.
In 1998, there were 412,000 deaths attributed
to breast cancer for women in the
world, representing 1.6% of all female
deaths. In terms of absolute numbers, the
greatest contribution is now from developing
countries, where 250,000 such deaths
occurred, as compared to developed
countries, which account for 160,000
deaths. However, the proportion of deaths
due to breast cancer in women remains
higher in the latter countries at 2.0% in
comparison to 0.5% in the developing
countries. Male breast cancer is about
100 times less frequent than the disease
in women.
The Netherlands exemplifies the high incidence
of breast cancer in developed countries,
with an age-standardized incidence
rate of 91.6 new cases per 100,000
woman-years, but there are sub-populations,
such as white women in California,
which exhibit age-adjusted incidence
rates of 100 or more. Overall, the incidence
rate in the USA is estimated at
91.4. Such high rates are also observed in
Europe, Australia and New Zealand, and in
< 36.0
< 54.2
Age-standardized rate/100,000 population
< 91.6
Fig. 5.13 Risk of breast cancer is decreased in
women who have children early and who have
breast-fed.