Ethnicity And The Tumour Characteristics Of Breast Cancer In A Large Nationally Representative Sample Of Women In England

Toral GATHANI, University of Oxford, United Kingdom

1 Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, UK
2 Department of Oncoplastic Breast Surgery, Oxford University Hospitals NHS Trust, Oxford, UK

Some studies have suggested that ethnic minority women have more aggressive breast cancer compared to White women.  However the evidence is limited and inconsistent, and generally has not accounted for sociodemographic differences.  Complete data on tumour characteristics by ethnicity are available for over 68000 breast cancers registered in England between 2006 and 2013 and are reported here.
The data analysed includes patient characteristics (age/ deprivation/ethnicity) and tumour characteristics (size/grade/ nodal status/receptor profile).  For each tumour characteristic logistic regression yielded odds ratios (OR) by ethnicity adjusting for age, region, deprivation, and all other tumour characteristics.
There were 66,192 breast cancers in White women, 1233 in South Asian women and 641 in Black women.  The mean age at diagnosis was on average five years younger in South Asians and Blacks compared to Whites (55 versus 60 years).  In unadjusted analyses, both South Asian and Black women were more likely than White women to have higher risks of more biologically aggressive tumour factors including higher grade, larger size, ER negativity and node positive tumours. However after adjustment for age in particular, and other factors, these differences between the ethnic groups were reduced substantially.  For example, compared to White women, the unadjusted and adjusted OR for tumours >5cm was 1.23 and 1.03 (NS) for South Asian women, and 2.05 and 1.44 (NS) for Black women. Similarly, compared to White women, the unadjusted and adjusted OR for node positive cancers was 1.23 and 1.03 (NS) for South Asian women and 1.6 to 1.2 (NS) for Black women.  
This study provides large scale nationally reliable data on the association between ethnicity and different tumour characteristics of breast cancer.  Much of the apparent differences in tumour characteristics by ethnicity are due to differences in age at presentation.
Funding: CRUK