See below... Yes, a staging system is used for many types of cancer including leukemia; however, the factors involved are numerous and staging also depends heavily on the specific type of leukemia. Therefore, the staging for each particular case should be performed under the guidance of a hematologist/oncologist.
CLL Staging. There are different stages of cll which is staged using the rai or binet systems. This type of staging is helpful in determining prognosis and in making decisions regarding treatment. The details of the staging systems for cll can be found here: http://www.Cancer.Gov/cancertopics/pdq/treatment/cll/healthprofessional/page2#section_10.
Not really. If you are referring to acute leukemia, by definition, it starts in the marrow so this would be considered stage iv sometimes chronic myelogenous leukemia (CML) is referred to in stages: chronic, accelerated and blast phases which show increasing severity of disease and higher mortality.