I can understand with your mother's background in hospice care why she would make the decision not to go through the treatment. As has been mentioned before, there are no guarantees even after going through the rigors of treatment. Has she discussed with the doctors what palliative radiation &/or chemotherapy might be available to her as the disease progresses? I was caregiver to my husband who went through the prescribed treatment and still died within a year of starting treatment. His time following treatment was very difficult as he never regained his ability to eat and suffered severe depression. From a caregivers point of view his symptoms in his last 2 weeks of life were manageable at home but could not get doctors to express an opinion on what problems I might encounter eg. severe shorness of breath, massive bleed, to help me prepare for a crisis. Fortunately I had many years of hospice experience to help me. If I were given this diagnosis myself I am not sure what decision I would make, and I hope I never have to. I hope this is of some help though I know you are looking for someone who has not taken any treatment.
Wishing you strengh and courage to face the days ahead.