Hi Scientist,
I have done a lot of travel with metastatic disease. The information on the website is pretty comprehensive, and I don't think it is possible to insure for anything MBC related. That said, Australia has reciprocal arrangements with a number of European countries so your medical treatment would be covered. I always self-insure to a degree, in that I like to know I could quickly be put on a plane home if necessary. I don't usually book too far ahead either. Just in case.
Go for it - well worth it!
Best wishes..... Pam