Public Health Bulletin Edition 1, 2004 - SA Health - SA.Gov.au

Figure one shows three-year moving averages for
both incidence and lung cancer-specific mortality; the data
has been adjusted for age to allow meaningful comparisons
.
The incidence of lung cancer reduced by about 25%
in males between 1977-80 and the late 1990s, and a
similar reduction is evident for mortality. By contrast,
females showed an approximate 60% increase in lung
cancer incidence over this period, with the majority of
this increase occurring before 1992. Female lung cancer
mortality shows a 50% increase before 1992, but with
no further increase thereafter.
Smoking is considered to be strongly associated with
squamous and small-cell lesions rather than with
adenocarcinomas. It is likely that the decrease in males
is due to reduced smoking, and this is supported by
Registry data which shows that the ratio of these cell
types fell from 2.4 to 1.5 over this period. By comparison,
there was little change in the ratio of these cell types in
females.
The incidence of diagnosed breast cancer has
increased by nearly 60% from 1977-80 to the present
time, due mostly to increases since the late 1980s that
followed the introduction of population-based
mammography screening. In the 50-69 year-old target
group, the increase was approximately 80%, with a
greater proportion being diagnosed when they were small
and more amenable to treatment.
Implications of this data for anti-smoking campaigns,
especially for women, are apparent. But lung cancer may
also be caused by exposure to asbestos, ionizing radiation
and other occupational carcinogens, and interventions to
limit exposure to these agents should be continued.
Time trends in three significant cancers
It is generally accepted that the application of a
successful cancer screening or early detection program
is followed by a significant reduction in cancer-specific
mortality. Figures 2, 3 and 4 show incidence and mortality
trends for cervical, breast and prostate cancers. Cervical
and breast cancers have been subject to formal screening
programs while prostate has been the subject of much
discussion and debate because of the widespread
application of a blood test (Prostate-specific Antigen)
followed by biopsy.
The incidence of cervical cancer has reduced by
nearly 40% from 1977-80 to the present time. This is
attributed to the detection and early treatment of precursor
lesions.
Cervical cancer-specific mortality rates have decreased
by 60% over the same period. Overall, the percentage
reduction in mortality was greater than the corresponding
reduction in incidence.
This effect is attributable to the application of early
detection methods in the early 1980s, and to the adoption
of formal screening after a series of successful pilot
programs.
Breast cancer-specific mortality rates reduced by
10% for all ages combined over the same period. Overseas
studies have shown that the impact of breast screening
on mortality rates can take several years to become
evident. Near full screening coverage for the SA
community was not achieved until 1991-1992. Within the
last two years 66% of women between 50 – 69 years of
age have been screened. Nonetheless, the agestandardised
mortality rate over the last three years was
20% lower than for the preceding decade in the 50-69
year olds. A smaller reduction of 10% applied to women
over 69 years of age, many of whom would have been
screened at a younger age. There has been no reduction
in mortality for women of less than 50 years of age. A
major challenge is to develop a cost-effective means of
screening these younger women, who tend to have
denser breast tissue. Other forms of imaging are being
investigated, as well as circulating tumour markers.
The incidence of diagnosed prostate cancer has
increased by nearly 95% between 1977-80 and the
present time, peaking in 1993. Most of this increase has
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