percentage of us who develop brain mets???

[gqmom]

Hi all,
I have been reading that 30-40% of women with Her2 positive BC develop brain mets. Is this correct?? Is that percentage for all of us or is it for people with more advanced cancer? Is that the personal risk or does it apply to a large group? I'm so confused...the more I read, the more confused I get!!!! I should stay off the computer and just listen to my onco, I guess.