Hello lauralable. I'm so sorry to read about your situation. It's especially awful that you're so young. To answer some of your questions it would be helpful if you could say what type of stereotactic RT you are having, and what your cancer is receptive to (i.e, is it ER+ or Her2+).
The thing about stereotactic RT is that it is so precise, it spares healthy tissue. As a result it can be used at a much higher dose than conventional RT (potentially at a curative dose). If you would like a bit more info about stereotacic RT, and patients who have benfitted from it you can go to:
www.ukcknetwork.co.uk
It's understandable that you are concerned treatment has not eradicated your symptoms, but please remember it takes a while for RT to reduce mets. People wrongly believe that RT burns the mets, and therefore has an instantaneous effect. In fact, RT works by disrupting the DNA of a cancer cell so that when it tries to reproduce it can't, so it then shrivels and dies. Consequently it will take a while before things resolve.
I had a type of stereotactic RT for skull mets called Cyberknife back in October 2010, and those mets have never come back. Unfortunately, I now have 5 small brain mets, and will probably be having stereotactic again in the near future. My cancer is Her2 receptive, so at the moment I'm taking a drug combination called Lapatanib and Capecitabine, which seems to be keeping things under control (Lapatanib is one of the drugs that can cross the blood brain barrier).
I know you must feel very sad, and worried at the moment, but your secondaries have been caught early, so with high dose stereotactic RT, and a good drug regime, you stand a good chance of dealing with this episode. The fact isthough that you do have secondary cancer and there is always the chance it will go somewhere else, but you can and will deal with it, like many others on this forum (many of whom have been dealing with cancer for many years).
Good luck with your treatment and let us know how you go.