brachial plexopathy

Looking for opinions - the neurologist here has scared me terribly.
EMG shows damage to the brachial plexus (as did EMG in March)
MRI is inconclusive metastatic disease or fibrosis (no mass shown)
Muscle weakness slowly progressing in Right arm as well as lymphedema. Seems to be along C5/C6 areas. No significant pain except thumb and forefinger which has been noticed in varying degrees at least 18 months.
Also VERY tight muscles in back (? due to poor posture and compensating for weakening arm muscles?) Therapist works on releasing scar tissue in upper back.
I was not even aware of muscle weakness until EMG in March that was done before carpal tunnel surgery (which did nothing for my finger numbness/pain)
History: breast cancer 4 years ago, mastectomy/node dissection, chemo, radiation, TRAM reconstruction.
Recurrence: dec. 2003 - one supraclavicular lymph node, one lung node <10mm. Responding well to Femara.
In the past year, I've had 1 PET scan, 4 CT scans, 2 CXR's, bone scan and nearly monthly doctor visits for cancer followup. No sign in any of that about tumor in brachial plexus.
(Pain in finger/thumb, muscle weakness limits mobility, tightness in arm and back muscle pain - all are very discouraging and overwhelming. THen the doctor casually mentions as he walks out of the exam room that it may be recurrent cancer (and that if it is "only" radiation, it will continue to progress to total paralysis of arm and untreatable pain.)
I could sure use some encouragment and some facts about all this.
I'm so frightened it is hard to be calm and logical.
Thanks

[CCF-Neuro-M.D.-CS]

Without examining you I cannot determine if this is a problem in the brachial plexus or a peripheral nerve. However, assuming that this is a problem with your brachial plexus, on the side of the cancer, then this could be due to tumor recurrence or radiation injury. There are other conditions as well, but I would require more history to determine if they should be considered. To evaluate this condition you could have a CT or MRI scan of the brachial plexus. If these modalities do not reveal a focal mass, to suggest recurrence, then a FDG-PET scan would be reasonable. Assuming no mass was found, and you had radiation to the area of the brachial plexus, then this could represent radiation injury. This condition typically starts with pain, and then can progress to loss of feeling and muscle function in various areas of the arm. The extent and progression of the process depends on the areas which were irradiated, and the areas of the plexus which are involved. In some patients complete loss of use of the arm can occur. A consultation with a neurologist who can help you sort this out would be reasonable. They may need to repeat your EMG to determine which areas of the plexus are affected. There is no specific treatment to reverese the radiation injury, but there are medical and surgical options for pain control. I hope this information helps, good luck.