Ethnic Breast Cancer Risk 'Due to Demographics'

Liam Davenport

March 14, 2016

South Asian and black women are diagnosed with breast cancer at a younger age than their white counterparts, and they are more likely to have aggressive tumors, according to the results of a nationally representative study in the United Kingdom.

However, the results, presented at the 10th European Breast Cancer Conference (EBCC-10), indicate that this disparity is largely due to demographic differences that will disappear over time.

Lead researcher Toral Gathani, MD, PhD, consultant oncoplastic breast surgeon at Oxford University Hospitals National Health Service Trust and clinical epidemiologist in the Cancer Epidemiology Unit at the University of Oxford, United Kingdom, explained that the age differences in diagnosis are due to South Asian and black women being "just younger" than white women.

Citing migration as the primary reason, she told Medscape Medical News: "The migrant population has very few people in their 70s and their 80s, so, over time, as these populations mature, you will start seeing that their average ages will become more similar to the indigenous population."

The consequence is that the average age of women of ethnic minority who present with breast cancer will be younger. "If you don't have women in their 80s getting breast cancer, your average age is going to be left-shifted," Dr Gathani said.

She added: "In the white population, you've got this whole population over the age of 80 getting breast cancer, so their average age is going to be higher. It's simply a function of the demographic.

"It's not that [women of ethnic minority] are more susceptible to the disease at a younger age, they are just young."

For the study, the researchers gathered data from Public Health England on all breast cancer cases registered in England between 2006 and 2013. The sample yielded 66,192 cases in white women, 1233 cases in South Asian women, and 641 cases in black women.

The researchers collated information on patient age at diagnosis, region of residence, and socioeconomic status, as well as tumor characteristics, including size, grade, nodal status, estrogen receptor status, and human epidermal growth factor receptor–2 (HER2) status.

The mean age at diagnosis was lower in South Asian and black women than in white women, at 55.0 years and 54.6 years, respectively, vs 60.4 years.

On unadjusted analyses, South Asian and black women were more likely than white women to have aggressive tumors at diagnosis, including tumors of higher grade and larger size, estrogen receptor–negative tumors, and node-positive tumors. However, these differences were substantially reduced on multivariate analyses that took into account age, socioeconomic status, region, year of diagnosis, and tumor characteristics.

For example, the unadjusted odds ratios for high-grade tumors among South Asian and black women vs white women were 1.49 and 1.94, respectively. These fell to 1.21 and 1.43, respectively, on multivariate analysis.

Similarly, the unadjusted odds ratios for tumors >5 cm in size were 1.23 for South Asian women and 2.06 for black women, which fell to 1.03 and 1.55, respectively, on multivariate analysis.

There were no differences in the likelihood of having HER2-positive breast cancer tumors between the ethnic groups.

For Dr Gathani, the younger average age at presentation for women of ethnic minority underscores the importance of their being "breast aware," particularly inasmuch as such women are known to have a lower overall risk for breast cancer and, owing to their age, are likely to be too young for routine breast cancer screening.

Nevertheless, differences in breast cancer biology at different ages mean that younger women are more likely than older women to have aggressive breast cancer at presentation. "So that's what I mean when I say it's important for them to be breast aware, to seek medical attention when appropriate, and to go to screening when it's offered," Dr Gathani said.

For Dr Gathani, the next step for research will be to use the dataset to look at survival differences and the impact of treatment in different ethnic groups.

She noted that "any data about ethnicity and breast cancer in the UK" indicate that women of ethnic minority have poorer outcomes, adding: "Whether it's all a function of them having more biologically aggressive disease at presentation or just simply because they're younger I don't think has really been answered."

Commenting on the study, Lisa A. Newman, MD, MPH, director of the Breast Care Center at the University of Michigan Comprehensive Cancer Center, Ann Arbor, said that the investigators should be "applauded for their pioneering work in looking at breast cancer patterns in the diverse population of England."

Noting the more advanced and higher-grade breast cancers in black and South Asian patients, she told Medscape Medical News that the researchers "appropriately concluded" that breast health awareness and screening should be "aggressively promoted" to these women.

In contrast, Dr Newman felt that the finding that black and South Asian women were diagnosed with breast cancer at a median age 5 years younger than their white counterparts "indicates that research regarding biologic and genetic variations in breast cancer related to ancestral background is also clearly warranted."

The authors and commentators have disclosed no relevant financial relationships.

10th European Breast Cancer Conference (EBCC-10): Abstract 4, presented March 10, 2016.

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