As noted earlier, adult acute leukemia is not a single disease. It is really a group of related diseases, and it is important to remember that patients with different subtypes of acute leukemia vary in their prognosis and response to treatment. Treatment options for each patient are based on the FAB subtype of the leukemia as well as certain prognostic features. These prognostic features include the patient's age, white blood cell count, cytogenetic test results, initial response to chemotherapy, and whether or not there was an existing preleukemic condition (myelodysplastic syndrome), or another cancer treated with chemotherapy, and/or without radiation therapy.