The comparative epidemiology of benign breast lumps and breast cancer in Western Australia

Abstract

Totals of 313 patients with breast cancer and 1,283 patients biopsied for benign breast lumps were found in Western Australia in 1978 through review of all histopathological, hospital and cancer registry records. The incidence of breast cancer rose to 146.9 per 100,000 at age 45-54 years and thereafter increased little. The biopsy rate for benign breast lumps rose more sharply to 420.2 per 100,000 at age 45-54 years and then fell. This pattern was mainly due to benign mammary dysplasia (BMD); fibroadenoma showed an earlier peak biopsy rate (30-34 years) and other (mainly non-neoplastic) benign lumps were biopsied at a relatively constant rate throughout adult life. Rates of breast cancer, BMD and fibroadenoma showed similar relationships to the other descriptive variables studied. The rates of each were higher in single than married women, in residents of the Perth area than residents of other parts of the State and in women employed in professional and related occupations than other employed women. They were lower in migrants from Europe (excluding Great Britain) than native-born Australians and in women of low socio-economic status than women of high status. Not all these differences were statistically significant. Rates of other breast lumps did not generally vary in these ways and were conversely related to country of birth, area of residence and socio-economic status. The parallels in descriptive epidemiology between breast cancer, BMD and fibroadenoma suggest that they may share aetiological factors.