Age and ethnicity as prognostic factors influencing overall survival in breast cancer patients in the Auckland region. Auckland Breast Cancer Study Group.

AIMS: to assess the effect of age at diagnosis and ethnicity on overall survival from breast cancer.
METHODS: information was collected from 2706 breast cancer patients in the Auckland region, diagnosed between 1976 and 1985. Age at diagnosis was categorised into four groups: < 35 years, 35-49 years, 50-74 years and 75 years or older. Ethnicity was self reported in three categories: European, Maori and Pacific Island Polynesian. Independent effects were assessed by controlling for extent of disease, specifically metastases at presentation, nodal status and size of tumour.
RESULTS: age and ethnic group were both significantly related to overall survival in univariate analyses. In multivariate analysis, age had an independent effect on survival mainly due to a significant survival difference between women aged less than 35 years and those aged 35 to 49 years (p < 0.0001; RR = 2.02). Survival was not significantly different between other age groups when adjustments were made for extent of disease. There was no significant effect of ethnicity on survival in the reduced dataset used for the multivariate analysis. Separate analyses suggested that ethnic differences in the extent of disease at diagnosis may be the cause of the apparent initial effect of ethnicity on survival.
CONCLUSIONS: women < 35 years at diagnosis have a significantly poorer prognosis than women aged 35-49 years. Other differences between age groups were not significant when stage of disease was taken into account. Ethnicity was not an independent factor influencing survival after controlling for extent of disease but numbers in the Maori and Pacific Island groups were too small to conclusively evaluate any effect of ethnic group on prognosis.