First of all, let's hope the blood levels rising is due to something else - it can be, you know. And MRIs are very tricky - they have a high degree of false-positives. What I'm saying is, it's good to be prepared, but don't assume you have cancer, because it could be a convergence of other factors.
If you do - if you had a lumpectomy and radiation last time, you won't have radiation again (if it's on the same side), you'd have a mastectomy. And depending on what chemo you had last time, you'll probably have a different one this time - maybe what they call "dose dense" chemo, which attacks cancer in a more aggressive way. Some types of chemo you can't have again, due to chance of heart damage; ask your doctor if you're at the limit for certain drugs, due to potential heart problems.
If tamoxifen and an aromatase inhibitor didn't work, PERHAPS they could try raloxifene, which I believe is like tamoxifen but supposedly better in some ways. You could ask about that. Also ask if you're HER2-neu receptive, in which case you could take Herceptin or Tykerb.
For other questions - have you tried Googling "breast cancer recurrence"? I'd think a lot would come up with that term.
Good luck to you - I hope it's NOT a recorrence. But if it is, stay connected here -we'll try to help. PJ Hamel