CANCER MANAGEMENT
54 CANCER CONTROL 2014
which is derived from classifying the Mexico's approximately
2,500 municipalities that vary greatly in population and
socioeconomic conditions, is closely aligned with the level of
poverty. The most recent index was calculated in 2010, using
census data, and the data presented below apply this
categorization retrospectively to the entire time series of
mortality data. Additional analysis was undertaken applying
earlier indices by period with little change in the overall
results.
Basic sensitivity analysis was also undertaken to take
account of possible bias from misclassification of uterine
cancer deaths. The trends over time are little affected by
sensitivity analysis that reclassifies a proportion of deaths
listed as cervix.i
Equity aspects of the women´s cancers transition
Both incidence and death from cervical cancer, a disease that
can be prevented,33 is increasingly concentrated among poor
women. At the same time, the burden of breast cancer is
rising in these same populations.
A recent analysis of the global burden of cancer in relation
to the Human Development Index (HDI), showed that breast
cancer incidence rates have been increasing in almost all
regions in the world, irrespective of the level of economic
development.25,34 By contrast, the incidence of cervical cancer
has been declining in most regions, including countries of
both higher and lower income, with the exception of only the
very poorest countries.
6,25 As a result of these diverging
trends, breast cancer has now surpassed cervical cancer to
become the most common female cancer in the majority of
countries with the exception of some of the poorest countries
where cervical cancer is still the most common cancer among
women. Consequently, regions made up predominantly of
low- and middle-income countries are facing a dual female
cancer burden - their historically high and persisting
incidence burden from cervical cancer as well as an emerging
high incidence burden from breast cancer. As survival from
both breast and cervical cancer are positively associated with
level of socioeconomic development, a greater proportion of
the mortality burden is also seen in less developed regions.
Long-run trend data on cancer incidence are sparse,35 but
existing information clearly demonstrates a cervical-breast
cancer transition, which began in high income countries (i.e. in
North America, Europe, Australia, New Zealand and Japan)
and is now evident in low- and middle-income countries (i.e.
all other regions). For instance, in Denmark, the age-adjusted
incidence of breast cancer surpassed that of cervical cancer
prior to the 1950s, with the differential growing due to the
marked increase in breast cancer over the next five decades
(Figure 1a). The cross-over in the age-adjusted incidence
rates of these two cancers occurred much later in Asian and
Latin American populations - e.g., only in the mid-1970s in
Osaka, Japan (Figure 1b), during the 1980s in Costa Rica
(Figure 1c), and in the early 1990s in urban India (Figure 1d).
The cervical-breast cancer transition, and its
consequences, can now be clearly observed in Africa, where
breast cancer has recently surpassed cervical cancer to
become the most common female cancer in the continent.36
Certain regions in Africa now have the added challenge of not
only the highest incidence and the highest mortality rates
from cervical cancer worldwide, but also the growing
challenge of breast cancer. Though breast cancer incidence
rates are lower than in wealthier countries, mortality rates
are much higher due to late detection and lack of access to
treatment (Figure 2).
In the case of Mexico, the women´s cancers transition for
women from the mortality data that span the period 1955 to
2010
5,37 shows mortality from cervical cancer peaked at
almost 17 per 100,000 women in the late 1980s and
subsequently fell continuously, reaching a low of just close to
7.5 per 100,000 women in 2010. By contrast, breast cancer
mortality rose steadily until the mid-1990s and has since
remained stable at a rate of approximately 9.5 per 100,000
women. These rates converged between 2005 and 2006 and,
since that point in time, breast cancer has been the leading
cause of cancer death in women.
The equity aspects of the women's cancers transition in
Mexico is most clearly seen by analyzing within-country
trends. The 32 states are classified into five categories
according to their level of marginality (a composite index of
poverty and access to basic services where high marginality is
associated with the greatest poverty). In the 1980s, the range
in marginalization-specific absolute differences in cervical
versus breast cancer rates was relatively small. This is largely
because cervical cancer mortality rates had not yet peaked in
the poorer states and because the middle-income states had
not passed far into the transition. By the late 1980s, the
overall pattern is quite clear: the absolute differences in the
i There is some evidence of imprecise coding of uterine cancer deaths due to
difficulties in identifying the origin of the cancer as cervix or corpus uteri.32
This could bias our results by underestimating the number of deaths
attributable to cancer of the cervix. This bias could be associated with
poverty, as miscoding may be more likely where training and human
resources for health are lower. Thus, basic sensitivity analysis was also
undertaken by reclassifying uterine cancer deaths in women below age 50 as
cervical cancer, the rationale being that cancer originating in the uterus is
very uncommon in younger women. The trends over time are little affected
by this reclassification.