Prognostic factors in women with breast cancer: inequalities by ethnicity and socioeconomic position in New Zealand

Abstract

To investigate differences in breast cancer prognostic factors between ethnic and socioeconomic groups in New Zealand. We analyzed all 21,586 breast cancer cases on the New Zealand Cancer Registry (July 1994-June 2004). Māori, Pacific, and non-Māori/non-Pacific women were categorized according to ethnicity on the Registry. Deprivation was analyzed as quintiles of the New Zealand Deprivation Index 2001, an area-based measure of socioeconomic position. Logistic regression was used to estimate age-adjusted odds ratios (OR) (95% confidence intervals (CI)). Māori and Pacific women were more likely to have non-local stage, less well differentiated cancer, larger tumors and positive human epidermal growth factor receptor-type 2 (HER-2) status than non-Māori/non-Pacific women. Māori were less likely and Pacific women more likely than non-Māori/non-Pacific women to have negative oestrogen (ER) and progesterone receptor (PR) status. Adjusting for deprivation did not materially alter the results. Women living in more deprived areas had a higher risk of non-local stage and larger tumors. These associations were only partially explained by ethnicity. There was no relationship between tumor grade, ER, PR or HER-2 status and deprivation. Our results confirm that Māori, Pacific and low socioeconomic women present with poor prognosis breast tumors.