AMSTERDAM, Netherlands-Differences in the aggressiveness of breast cancer between ethnic groups in England are mostly caused by differences in median ages of women in these groups rather than by ethnicity, according to research reported at the 10th European Breast Cancer Conference (Abstract 4).
Toral Gathani MD, MBBS, FRCS, a consultant oncoplastic breast surgeon and clinical epidemiologist at Oxford University's Cancer Epidemiology Unit, reported an analysis of breast cancers registered in England between 2006 and 2013 with 66,192 tumors in white women, 1,233 in south Asian women, and 641 in black women.
"Much of the apparent excess of aggressive breast tumors in south Asian and black women is simply because they are younger than white women," Gathani said in a news briefing, explaining this reflected the fact that these groups included recent migrants and that in time the breast cancer differences between ethnic groups would likely diminish.
Tumors were diagnosed at lower median ages among women in the two ethnic minorities (55.0 years for south Asian, 54.6 years for black) than in white women (60.4 years).
"Breast cancer is more aggressive in younger than older women, and this largely explains why more aggressive tumor features were seen in ethnic minorities," she said.
Aggressive Tumors
The study analyzed tumor characteristics including size, grade, nodal status, estrogen receptor (ER) status and human epidermal growth factor receptor 2 (HER2) status in each of the three ethnic groups. The crude data were then adjusted for age at diagnosis, region of residence, social deprivation, and other tumor characteristics.
South Asian and black women were found to be more likely than white women to have biologically aggressive tumors including those with higher grade, larger size, ER negativity, and node positivity, Gathani reported. But there was little difference between ethnic groups after adjustment for a range of factors-particularly age.
After adjustment, the chances of finding tumors up to five centimeters diameter were no greater among South Asian women than in white women. In black women, the adjusted risk of breast cancer was down from the double that in white women to only 50 percent higher after being adjusted.
After adjustment, the odds of having a node-positive cancer in south Asian women were only 16 percent higher than in white women, down from 32 percent higher before adjustment. And in black women, adjustment brought node-positivity odds down from 60 percent higher to only 20 percent higher than in whites. There were no differences between ethnic groups in the risk of having HER2 positive tumors.
Socioeconomic factors had little influence and Gathani reported breast tumors were slightly larger in ethnic minority women than in white women, even after adjustment for age. She hypothesized this may have been due to delays in diagnosis, such as not having been screened or having prolonged duration of symptoms before seeking medical attention.
"Ethnic minority women should be encouraged to be breast aware, to attend regular screening at the appropriate ages, and to see their doctors if they have concerns," she said.
Minorities & Breast Cancer
At a news briefing, Fatima Cardoso, MD, Chair of EBCC10 and Director of the Breast Unit at the Champalimaud Clinical Centre in Lisbon, Portugal, said that, since studies with African-American women with breast cancer pointed to a worse prognosis overall than white women, it was important to discover whether this was because the biology is different, or because the women are just younger and therefore tend to have breast cancer with more aggressive biological features.
"This study suggests that the worse prognosis seen in breast cancer patients from ethnic minority groups in the U.K. can be at least in part explained by the younger age of this group."
But she wasn't convinced that age by itself determined prognosis. She told Oncology Times that, since other studies had shown women from ethnic minorities get more breast cancer at younger ages, there was a need to confirm these studies in different countries. "[We need to] compare black woman in Africa with black women in the U.S. or the U.K., try to understand if it's a genetic hereditary trait, the impact of the environment, or a mix of both that leads to a different biology of breast cancer in black women," she said.
When Cardoso was asked if inequality differences, economic disadvantages, and access to care could be factors causing breast cancer differences between ethnic groups she said she wasn't convinced, citing evidence from African women living in Africa among whom triple negative breast cancer rates seemed to be higher than among their African-American counterparts.
"It's probably a mix of both factors," she noted.
And she thought age was important for another reason, namely that young women can sometimes be overtreated just because they are young.
"And one thing that's important is that before age comes biology," she said, adding that if a "good biology" tumor appears in a young women it "does not mean that you have to overtreat just because she is young." She added that if a young woman has a "good biology tumor" she should not be overtreated.
When Cardoso was asked for her take-home clinical message she said, "You cannot forget about breast awareness just because a woman is younger."
And she added that, independent of ethnicity, women and their doctors needed to have breast awareness. Which was "very important" for women of all ages.
Peter M. Goodwin is a contributing writer.