BREAST-CANCER MORTALITY TRENDS IN AUSTRALIA - 1921 TO 1994

Objective: To analyse breast cancer mortality trends in Australia and to see if mammographic screening has yet led to a reduction in mortali ty. Design: Retrospective analysis of trends in mortality rates from b reast cancer in Australian women between 1921 and 1994, and in potenti ally explanatory variables such as fertility, body size, age at menarc he, and screening. Results: Changes in breast cancer mortality in Aust ralian women could not be explained by chance variation alone. Mortali ty rose steadily (average annual increase, 1.0%) to 1940-1944, fell to the 1960s and early 1970s, and rose (average annual increase, 0.3%) t o the late 1980s. Between 1985-1989 and 1990-1994, breast cancer morta lity fell by 3.2% in women 50-69 years of age (the target age group fo r mammographic screening) and by 4.2% in women 25-49 years of age. The re was almost no change (-0.2%) in breast cancer mortality in older wo men in this period. The proportion of women screened in all age groups increased substantially between 1988 and 1994; nearly 65% of women in the target age group had had at least one mammogram by 1994. Decrease s in fertility were followed by increases in mortality, and vice versa . Conclusions: Trends in breast cancer mortality have probably been in fluenced by changing fertility, nutrition and body-size increases amon g Australian women. Improvements in stage at diagnosis and treatment h ave probably moderated the upwards pressure on mortality caused by an increasing incidence. Recent falls in mortality could be expected to c ontinue as more women participate in the mammographic screening progra m. This trend should be more clearly evident in the second half of the 1990s.