My Dad Has Been Diagnosed With Acute Leukemia About A

my dad has been diagnosed with acute leukemia about a month ago, they started a chemo through shots in the stomach, after just 2 sessions he's back in the hospital and his health is failing very fast. He's 73 and in what we would consider good health. He hasn't eaten in almost 4 days, came down with c diff and hospice has been called in. what kind of time frame are we looking at ?