The side effects of any drug or other treatment for cancer, in this case leukemia, aren't fun.
Each individual reacts differently to various cancer treatments.
Unfortunatley, I believe science has not yet found a drug that attacks only the cancer cells, although I think there has been advancements. Research continues.
From just a quick look, it seems the patient survival rate on Imatbib (aka Gleevec) after 30 months is an astounding (to me at least) 91% plus. The 5 year survival rate is high also. I think around 85%
Those with untreated acute myelogenous leukemia only live for months without treatment.
Hope that helps with any confusion.