Female breast cancers are getting smaller, but socio-demographic differences remain.

OBJECTIVE: To investigate trends towards early detection of infiltrating ductal carcinomas, possible effects on patients' prognosis, and characteristics of women still at high risk of late detection.
METHODS: South Australian Cancer Registry data were analysed to compare breast tumour diameters for the 1980-86 and 1997-2002 diagnostic periods by age. Relative survivals for 1980-86 were compared with corresponding survival estimates for 1997-2000, obtained by weighting diameter-specific survivals for 1980-86 to equate with the diameter distribution for 1997-2002. Multivariable logistic regression was used to determine socio-demographic predictors of large diameters (> or =30 mm) in 1997-2002.
RESULTS: The proportion of tumours with diameters smaller than 15 mm increased from 13.0% in 1980-86 to 36.7% in 1997-2002, whereas the proportion with large diameters reduced from 43.0% to 18.6%. Estimated changes in 20-year survivals equated with a 33% reduction in breast-cancer mortality among patients aged 50-69 years at diagnosis. Data for 1997-2002 indicate that early diagnosis is not evenly distributed, with large diameters more common in age ranges outside the 50-69 year target for mammography screening; low socio-economic areas; non-Caucasians; patients born in northern/eastern Europe and potentially Asia/Middle East; and in some country locations. CONCLUSIONS AND IMPLICATIONS: Increased emphasis on early detection should be directed at sectors of the population where delays in diagnosis and poorer prognosis are evident. Projected reductions in breast-cancer mortality among patients are indicative of effects of earlier detection on patients' prognosis, but require confirmation with follow-up data. More particularly, parallel studies of effects on population-based mortality are warranted.