2-CHLORODEOXYADENOSINE TREATMENT AFTER SPLENECTOMY IN PATIENTS WHO HAVE MYELOFIBROSIS WITH MYELOID METAPLASIA

2-Chlorodeoxyadenosine (2-CdA) is a purine nucleoside analogue with th erapeutic activity in low-grade lymphoproliferative disorders. In addi tion, 2-CdA has a potent myelosuppressive effect, and it has been show n to be toxic to malignant myeloid cells both in vitro and in vivo. In this pilot study we treated nine patients who had advanced myelofibro sis with myeloid metaplasia (MMM) and progressive hepatomegaly or symp tomatic thrombocytosis after therapeutic splenectomy. 2-CdA was admini stered at 0.05-0.1 mg/kg/d for 7 d for one to five treatment cycles, A reduction in liver size associated with marked improvement in fatigue and control of thrombocytosis and leucocytosis was achieved in seven of the nine patients (78% response rate). In four of the seven respond ing patients the reduction in liver size was durable (4-28 months) and was associated with a decrease in serum alkaline phosphatase levels. However, no patient had improvement in anaemia, and two of the seven i nitially responding patients hare since died of acute leukaemia or pro gressive disease. improvement in bone marrow fibrosis was noted in two of fire available posttreatment marrow examinations. Toxicity was mai nly myelosuppression, which was severe in two patients, 2-CdA may be c onsidered a palliative therapeutic agent after splenectomy in noncytop enic patients with MMM who have progressive hepatomegaly or extreme th rombocytosis.