Patients with Chronic Myeloid Leukemia (CML) typically a translocation between chromosome 9 and 22 – resulting in what is called the philadelphia chromosome. At Asian Cancer Institute, we know that this is not enough information to treat patients correctly. As the time passes, addtional chromosomal abnormalities (ACA) can emergence and need to be monitored. Based on the six most common ACAs we can divide the CML patients into two groups: Group 1 with a relatively good prognosis including trisomy 8, -Y, and an extra copy of Philadelphia chromosome, and Group 2 with a relatively poor prognosis including i(17)(q10), -7/7q (-7/del7q), and 3q26.2 rearrangements. Patients in Group 1 have a much better treatment response and survival than patients in Group 2. The concurrent presence of two or more ACAs (even if from Group 1) conferred an inferior survival and such patients are considered as having poor prognosis. This is how we tailor the treatment for individual CML patients to maximise outcome.