CNS Leukaemia in Blast Cell Crisis in CML and Philadelphia (Ph′) Positive Acute Lymphoid Leukaemia

Fourteen cases of Philadelphia (Ph′) chromosome positive CML blast crisis, originally described by Janossy et al. (1976) were followed to determine the incidence of CNS leukaemia. The incidence was higher in those with lymphoid (L-type) blast crisis (three out of eight cases). The study was then extended to a random selection of cases, all of whom had had cell marker analyses carried out. Six out of 34 cases (approximately 18 per cent) of Ph′ positive acute lymphoid leukaemia (ALL) or L-type blast crisis who had cells expressing the ALL antigen (ALL+ cells) present during the course of their illness developed CNS leukaemia. Thirty-eight patients with myeloid (M-type) transformation did not develop CNS disease. The blast cell characteristics, clinical course and haematological findings are described in these patients. CNS leukaemia occurred between 5 and 11 months after diagnosis. Five out of the six cases had obtained remission with vincristine and prednisolone (V and P). Such patients should be treated as adult ALL and CNS prophylaxis should be given as soon as remission is achieved.