Background: Few studies have compared ovarian cancer rates between different ethnic groups in the same country. The aim of this study is 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 to 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 (11.2 per 100,000, 95% CI 9.5-14.0), intermediate in Mâori women (10.1, 95% CI 8.8-11.5), and lowest in non-Mâori, non-Pacific women (9.4, 95% CI 8.9-9.7). Age-standardised mortality rates showed the same pattern: 6.3 (95% CI 4.6-8.0) deaths per 100,000 in Pacific women, 5.8, (95% CI 4.7-6.9) in Mâori women, and 4.8, (95% CI 4.5-5.0) in non-Mâori, non-Pacific women. Ovarian cancer sub-types differed by ethnic group. There was no significant association between socio-economic deprivation and tumour grade or stage. Age-adjusted models showed that Mâori women were more likely to have well differentiated tumours (OR 1.53, 95% CI 0.77-3.03) and less likely to present at a later stage (OR 0.86, 0.64-1.16) compared to non-Mâori, non-Pacific women. These patterns were partly explained by socio-economic deprivation, and were not apparent for Pacific women.
Conclusions: Pacific and Mâori women experience higher incidence of ovarian cancer and mortality, compared to non-Mâori, non-Pacific women. Mâori women seemed to have better prognostic factors (local stage and well differentiated tumours) than non-Mâori, non-Pacific women. More work is needed to improve current cancer prevention strategies, particularly in Pacific women.