Breast cancer in New South Wales in 1972-1995: Tumor size and the impact of mammographic screening

To examine the use of mammographic screening in women in New South Wales (N SW), we measured uptake of initial mammograms and estimated the proportions of breast cancers that were screen detected. To see if mammographic screen ing has been associated with reductions in advanced breast cancers and mort ality from breast cancer, we analyzed trends in age-specific and age-standa rdized breast cancer incidence and mortality from 1972 to 1995 and tumor si ze in 1986, 1989, 1992 and April to September 1995. Between 1984 and the en d of 1995, an estimated 72% of NSW women in their 50s and 67% in their 60s had had at least 1 mammogram and, in 1995, an estimated 39% of invasive bre ast cancers in women in these age groups were detected by mammography, Befo re 1989, breast cancer incidence increased only slightly (+1.3% annually) b ut then, from 1990 to 1995, increased more rapidly (+3.1% annually). Betwee n 1986 and 1995, rates of small cancers (< 1 cm) increased steeply by 2.7 t imes in women 40-49 years of age and 5.6 times in women 50-69 rears of age. The incidence of large breast cancers (3+ cm), after little apparent chang e to 1992, fell by 17% in women 40-49 years of age and 20% in those 50-69 y ears of age to 1995, Breast cancer mortality increased slightly between 197 2 and 1989 (+0.5% annually) but then fell (-2.3% annually) from 1990 to 199 5. We concluded that breast cancer rates had been influenced in expected di rections by the introduction of mammographic screening in women resident in NSW, We expect that recent falls in incidence of larger breast cancers and breast cancer mortality will become steeper as screening coverage increase s in the second half of the 1990s. (C) 1999 Wiley-Liss, Inc.