Wednesday October 23 2013
Breast cancer is the most common cancer in the UK
"Black women at greater breast cancer risk," The Daily Telegraph reports.
The warning follows a new UK study that found that young black women (under 41 years of age) had worse breast cancer outcomes compared with young white women.
The study confirmed previous research that showed that black women tend to have more aggressive tumours. It also found that breast cancer was more likely to reoccur in black women.
In general, young black women had poorer relapse-free survival compared with young white women, even after the researchers adjusted their findings for factors such as body mass index, tumour size and whether the cancer had spread to the lymph nodes.
There were no significant differences in overall survival or breast cancer reoccurrence between white and Asian women.
Further research is needed to understand why black women had poorer outcomes, and what can be done to improve their chances. The researchers speculate that there could be both genetic and social factors involved, citing, for example, that immigrant women may be less likely to register with a GP.
Where did the story come from?
The study was carried out by researchers from the University of Southampton and University Hospital Southampton Foundation Trust, the Centre for Statistics in Medicine, and Barts and The London School of Medicine and Dentistry. It was funded by the Wessex Cancer Trust, Cancer Research UK and the National Cancer Research Network.
The study was published in the peer-reviewed British Journal of Cancer.
Reporting of the research by the BBC and The Daily Telegraph was accurate.
What kind of research was this?
This was a cohort study. It aimed to compare breast cancer tumour pathology, treatment and outcomes between three ethnic groups (white, black and Asian) of young breast cancer patients in the UK who were managed within the NHS.
A cohort study is the ideal study design to address this question, but cannot conclusively prove that differences in outcomes were caused by differences in ethnicity. There may be other factors (called confounders) that could be responsible.
What did the research involve?
Between 2000 and 2008 the researchers recruited into the study 2,915 women who were aged 40 or younger when diagnosed with breast cancer. They collected information on personal characteristics, including self-reported ethnicity, tumour pathology (for example how aggressive the tumour was and how large the tumour was) and treatment data.
The women were followed up and data, including date and site of disease recurrence, was collected annually until death or they were lost to follow-up. At the time of analysis, follow-up ranged from one month to 11 years, with an average (median) follow-up of five years.
The researchers calculated overall survival and relapse-free survival (survival without recurrence of breast cancer).
What were the basic results?
Of the 2,915 women included in the study, 2,690 (91.0%) were white, 118 (4.0%) were black and 87 (2.9%) were Asian. Patients from mixed ethnic groups were excluded.
Median tumour diameter at presentation was greater in black women (26mm) than white women (22mm).
Multifocal tumours (breast cancer where there is more than one tumour) were more frequent in black women (43.4%) than white women (28.9%).
Triple negative tumours were more frequent in black women (26.1%) than white women (18.6%). Triple negative tumours are tumours that don’t express the oestrogen receptor (ER), progesterone receptor (PR) or HER2. This makes them more challenging to treat because they don’t respond to hormonal treatment.
Most patients had surgical treatment, although rates for breast conserving surgery were higher in white women compared with black women. The use of chemotherapy was broadly similar in all three ethnic groups, with differences reflecting the stage of disease at diagnosis.
Overall and relapse-free survival
Five-year relapse-free survival was significantly lower in black women (62.8%) than Asian women (77.0%,) or white women (77.0%).
Five-year overall survival for black women was significantly lower than for white women (71.1% versus 82.4%). Five-year overall survival for Asian women was between that of black women and white women and was not significantly different from either.
The researchers then adjusted their results for factors that could have influenced results, including:
- body mass index
- tumour size
- grade (determined by what the tumour cells look like under the microscope, and whether they have features of a slow-growing or fast-growing cancer)
- nodal status (whether the cancer has spread to the lymph nodes)
Even after adjustment, black ethnicity was still associated with poorer relapse-free survival compared with white ethnicity. In other words, breast cancer was more likely to reoccur in black women (hazard ratio (HR) 1.50, 95% confidence interval (CI) 1.06 to 2.13).
Oestrogen receptor positive and negative breast cancers were then analysed separately. Black ethnicity was not significantly associated with poor relapse-free survival in women with ER-negative breast cancer but was significantly associated with poor relapse-free survival in women with ER-positive breast cancer (HR 1.60, 95% CI 1.03 to 2.47).
How did the researchers interpret the results?
The researchers concluded that “Black patients have an increased risk of breast cancer recurrence than white patients despite equal access to health care including adjuvant therapies. Black ethnicity is an independent risk indicator of poor prognosis in young women with invasive breast cancer, suggesting that current treatment approaches may be less effective in this population. Further studies are required to investigate this in more detail and to optimise the management of this patient group”.
This study has found that young black women had poorer five-year overall survival and relapse-free survival than young white women. Outcomes remained worse even after factors which could potentially influence the results were taken into account.
There were no significant differences in overall survival or breast cancer reoccurrence between women of white and Asian ethnicity.
This study compared outcomes of different ethnic groups in an age group that is not eligible for breast screening and in a population that receives entirely public-funded healthcare, thus eliminating a number of potential confounding socio-economic factors. However, although the proportion of black patients in the cohort is similar to the English population as a whole, the cohort only contained a small number of black and Asian women.
Further research will be required to determine why these black women may have had poorer outcomes, and whether steps can be taken to improve cancer outcomes for black women.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.