Characteristics of ovarian cancer in women residing in Aotearoa, New Zealand: 1993-2004.

Background: Few studies have compared ovarian cancer rates between different ethnic groups in the same country. The aim of this study was to describe ethnic patterns in the incidence and mortality of ovarian cancer in New Zealand, and to investigate ethnic and socioeconomic differences in the grade and stage of ovarian cancer.

Methods: Data on all women registered with ovarian cancer on the New Zealand Cancer Registry (1993-2004) were analysed. Population data were taken from the 1996 and 2001 census. Logistic regression was used to estimate associations between ethnicity, deprivation and tumour characteristics.

Results: Age-standardised incidence rates were highest in Pacific women, intermediate in Māori women, and lowest in non-Māori, non-Pacific women. Age-standardised mortality rates showed the same pattern. Ovarian cancer subtypes differed by ethnic group. There was no significant association between socioeconomic deprivation and tumour grade or stage. Age-adjusted models showed that Māori women were more likely to have well-differentiated tumours and less likely to present at a later stage compared to non-Māori, non-Pacific women. These patterns were partly explained by socioeconomic deprivation, and were not apparent for Pacific women.

Conclusions: Pacific and Māori women experience higher incidence of ovarian cancer and mortality, compared to non-Māori, non-Pacific women. Māori women seemed to have better prognostic factors (local stage and well-differentiated tumours) than non-Māori, non-Pacific women. More work is needed to improve current cancer prevention strategies, particularly in Pacific women.