Young black women in the UK diagnosed with breast cancer aged 40 or younger have poorer overall survival than white women in the same age group, according to a Cancer Research UK study published in the British Journal of Cancer.
The researchers, based at the University of Southampton, found that young black women have a higher risk of breast cancer coming back than white women, despite having the same access to healthcare.
The study also shows that this group are more likely to have larger tumours and higher rates of triple negative breast cancer – a type of breast cancer that does not respond to hormone therapies, and they tend to have more aggressive tumours.
But, even when these factors are taken into account, they do not completely explain why black women have poorer outcomes, particularly those with the type of breast cancer that is expected to be sensitive to hormones.
Although the exact reason for this difference is unknown, the study authors put forward a number of possible explanations as to why black women may be more affected than other groups.
It is possible that it could be explained by an as-yet unidentified biological factor such as cancers in women of African-Caribbean descent responding less well to treatments, including hormone therapy or differences in the genetics of their tumours.
Early diagnosis may also play a role if black women are less aware of the symptoms or less likely to be breast aware, enabling them to find any worrying changes. This could mean their cancer is diagnosed at a later stage which would reduce the chance of successful treatment and recovery.
And although treatment on the National Health Service (NHS) is designed to be equal for all, some cultural factors such as recent immigration to the UK or language barriers may in practice affect use of health services.
Dr Ellen Copson, a Cancer Research UK scientist and one of the study authors, said: "Our study confirms for the first time that black women under 41 in the UK are more likely to have breast cancer recurrence than their white counterparts, despite equal access to healthcare.
"The finding also backs up similar findings in the USA, suggesting that this could be an international trend, but further research is needed to try and pin down the exact cause or causes, so we can tackle this issue."
Dr Julie Sharp, Cancer Research UK's head of health information, said: "It's worrying that ethnic background may be a factor influencing a woman's chance of surviving breast cancer. We know that some ethnic populations carry higher genetic risks of getting certain types of breast cancer, but if this difference is down to symptom awareness or access to healthcare, that is particularly concerning.
"More research is needed to look into the reason why young black women have higher rates of recurrence, but in the meantime women of any ethnic background should be aware of what is normal for their breasts and get any new lumps or anything unusual checked out by their GP. More often than not breast changes won't mean cancer, but it's best to get any unusual changes checked out."
Copson, E et al. Ethnicity and outcome of young breast cancer patients in the UK: the POSH study (2013) British Journal of Cancer. DOI: 10.1038/bjc.2013.650