Breast cancer incidence and determinants of cancer stage in the Western Cape.

OBJECTIVE: To describe the overall and age-specific incidence rates for breast cancer and determinants of the stage of breast cancer at the time of diagnosis in the Western Cape, South Africa. METHODS: Data were derived from a case-control study of the association between injectable progestagen contraceptives and breast cancer conducted over a 4-year period from January 1994 to December 1997. In all, 485 cases were drawn from a study population consisting of coloured and black women under the age of 55 years, who presented with a first occurrence of invasive breast cancer at two tertiary hospitals in Cape Town. A questionnaire was administered and information on a large number of variables was recorded. RESULTS: The 249 cases who were interviewed during the first 2 years of the study constituted the numerator for estimates of incidence rates. The overall incidence rate was 23.1 per 100,000 women per year. The incidence rate for coloured women was 25.6 per 100,000, almost twice that for black women (14.7 per 100,000). The incidence rate in urban areas was 26.6 per 100,000, almost twice that in the rural areas (16.3 per 100,000). Stages 1 and 2 accounted for 57.8% of the cases. Early stage at diagnosis was significantly associated with a higher educational level, membership of a medical aid, residence in an urban area and a positive family history. CONCLUSION: The data suggest that there is scope for improvement in the detection of the disease through education and access to diagnostic measures, particularly in rural and disadvantaged populations.