My dad was diagnosed with Acute myeloid leukaemia (Acute myeloid leukaemia (AML)) in December, he is 73 and was 72 at the time, he underwent intense chemotherapy multiple times and given how healthy he is and how he came through it we were led to believe in January that one last deep clean of intense chemo would clear it, they were wrong and it was still there but in his bone, because of how strong and fit he was considered for a transplant but eventually was ruled out, this left us one option of long term chemo tablets for a year then we see, sorry for the whole story but my question is, my dad finally got to a point where the chemo and meds were balanced and his bloods returned to normal levels for the last 7 months, now though, bloods are showing discrepancies and they immediately took a bone marrow sample, what does this mean