Purpose: To determine the endometrial cancer rates, and the proportion attributable to diabetes mellitus (DM), physical inactivity, and overweight/obesity, by ethnicity with a focus on Pacific women in New Zealand.
Methods: Linked census-cancer records (1981-2004) were used to determine incidence rates of endometrial cancer by ethnicity. Health survey data (2006-2007) were used to determine risk factor prevalence by ethnicity. Relative risks for the association between diabetes, obesity, physical inactivity and endometrial cancer were sourced from published studies. Population attributable risk (PAR) methods, with Monte Carlo simulation, were used to estimate the PAR% by ethnicity and applied to 2001-2004 cancer rates.
Results: Pacific women had 2.61 (95 % confidence interval 2.22-3.05) times the endometrial cancer rate of European/Other women pooled over time, and the most rapidly increasing rates over time with the rate ratio increasing from 1.96 (1.14-3.37) in 1981/1986 to 3.78 (3.03-4.71) in 2001/2004 (p for trend = 0.14). Pacific women had the highest PAR% for DM, physical inactivity, and overweight/obesity (63.1 %), followed by Māori (58.6 %) and European/Other (48.6 %). Applying these PAR% to 2001-2004 endometrial cancer rates, the rate ratio comparing Pacific to European/Other endometrial cancer reduced from 3.8 for total cancer (attributable plus non-attributable) to 2.3 for non-attributable cancer, and the rate difference reduced by 79 % from 51 to 11 per 100,000.
Conclusions: Pacific women have high endometrial cancer rates in New Zealand. Some, but not all, of the ethnic inequalities were explained by measured differences in obesity/overweight, DM, and physical inactivity.