Incidence of ovarian and endometrial cancer by ethnicity in the Million Women Study

INTRODUCTION:   In the UK some have reported differences in the incidence of ovarian and endometrial cancer by ethnicity, but the extent to which these differences may be due to known risk factors is unknown.  In a large prospective study, we describe ovarian and endometrial cancer incidence by ethnicity, before and after adjustment for known risk factors for these cancers. 

METHODS: Women were recruited into the study in 1996-2001, when information on reproductive and lifestyle factors known to influence the risk of ovarian (C56) and endometrial (C54) cancer was obtained. They were followed up for an average of 12 years for cancer incidence. Cox regression models were used to calculate adjusted relative risks (RR) for incident ovarian and endometrial cancer among South Asians and Blacks compared to Whites.

RESULTS:  Analyses included 5,853 South Asian, 4,883 Black and 1,031,869 White women resident in England at recruitment. During follow up, incident ovarian cancer occurred in 24 South Asians, 36 Blacks and 6,521 Whites, and corresponding numbers for endometrial cancer were 52, 37 and 7,693. The relative risk of ovarian cancer was significantly lower in South Asians (RR 0.64 (0.43-0.95)) but not in Blacks (RR 1.16 (0.84-1.62)), compared to Whites after adjustment for known risk factors.  For endometrial cancer, the corresponding relative risks were 1.13 (0.86 – 1.50) for South Asians and 0.88 (0.64 – 1.22) for Blacks.

CONCLUSIONS:   South Asian women in England have significantly lower incidence rates of ovarian cancer than White women, which persists after adjustment for known risk factors for the cancer.  The incidence of endometrial cancer does not vary significantly in South Asians, Blacks and Whites.