BREAST-CANCER IN NSW WOMEN - A SHIFT IN TUMOR SIZE

Objective: To determine whether there has been an increase in the proportion of small (<1 cm in size) and localised breast cancers in woman aged 50-69 (the group actively recrutted to mammographic screening) compared with woman aged 40-49. Design: Cases of invasive breast cancer in woman aged 40-69 notified to the NSW Central Cancer Registry from histopathology reports. Results: A higher percentage of breast cancers were under 1 cm in size in 1992 (10%) than in 1986 and 1989 (7%). The increase in the percentage of small breast cancers was statistically significant in women aged 50-69 (chi(2) for linear trend, 7.9; P = 0.005), but not in those aged 40-49 (chi(2) for liner trend, 2.5; P = 0.12). Slightly more than half the breast cancers (53%) in 1992 were localised to the breast representing an increase from 49% in both 1986 and 1989. This increase was also statistically significant in women aged 50-69, (chi(2) for linear trend, 3.9; P = 0.05) but not in those aged 40-49 (chi(2) for linear trend, 1.4; P = 0.24). Conclusions: Breast cancers in 1986, 1989 and 1992 showed a moderately strong shift to smaller tumours and localised disease in women aged 50-69. As women of this age group were targeted by mammographic screening, the widespread availability of mammography may explain this shift.