It's a bit of a combination of more people living longer with metastatic breast cancer and the challenges of estimating a figure in the absence of incomplete data, but we don't believe more people are progressing to Mets than expected.
The 10,553 estimation of a national figure in our Making Metastatic Breast Cancer Count report was an estimation by epidemiologists using modelling and record linkage. They told us they felt this was probably an under-estimation and that they believe the real number was likely higher.
The reason we used the 10,553 figure is that they felt the data used to get to that number was solid and reliable (which is important when you are making big claims) and beyond that they couldn't be sure because of the lack of information available to them. They basically predicted a higher number but couldn't prove it, so we had to go with the safe estimate.
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