What would the general prognosis be for a patient with Chronic Myeloid Leukemia without treatment?

Considering I’m 18 years old and in remission from another cancer. I am also very underweight with a BMI of around 16 and I have generally pretty crappy health. I just want to know what the general prognosis would be, I know the cancer will kill me eventually if I’m not treated for it, but how long will that take? I really do NOT want to go through chemotherapy as it was brutal on me last time. I’m trying to weigh out my options I guess.