Page 0055

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.

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