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.
The study published in the British Journal of Cancer from researchers based at the University of Southampton found that young black women have a higher risk of breast cancer coming back than white women. This is 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, the report said.
The study authors said it was 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.
The resarch concludedsome 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: "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."
