Lead researcher Dr Sarah Walters, from the London School of Hygiene and Tropical Medicine, said the reasons for low overall survival in the UK and Denmark were different:
In Denmark, women are diagnosed with more advanced disease, but survival at each stage is similar to that in other countries. In the UK, women are diagnosed at a similar stage as elsewhere, but survival is lower than women with the same stage of disease in other countries.
In the UK, we should now investigate whether the treatment of women with later-stage breast cancer meets international standards. There is particular concern that this is not the case, especially for older women.
More top news
Police have offered legal advice to anyone who spots a dog trapped in a hot car - including on whether they can smash the windows or not.
Sir Nicholas Winton, who rescued 669 children from the Nazis, didn't tell anyone about his exploits for 50 years - not even his wife.
Police believe one of the West's most infamous criminals, timeshare fraudster John Palmer, was murdered.