Summary. We analysed CD56 expression in 70 patients with multiple myeloma (MM) to determine its clinicopathological and prognostic significance. Fifty-five (79%) patients were CD56 + . CD56 -patients (n ¼ 15) had higher b 2 microglobulin levels and a higher incidence of extramedullary disease, Bence Jones protein, renal insufficiency and thrombocytopenia than CD56 + patients. Their myelomas more frequently had a plasmablastic morphology. Overall survival was significantly lower in CD56 -than CD56 + patients (22 vs 63 months, P ¼ 0AE0002). We conclude that CD56 -MM is a discrete entity associated with more aggressive disease. The higher incidence of plasmablastic cases suggested that CD56 -MM may develop from a less mature plasma cell than CD56 + MM.

Recent studies have shown that arsenic trioxide (As 2 O 3 ) can induce complete remission in patients with acute promyelocytic leukemia (APL). We tested the efficacy and safety of As 2 O 3 for the treatment of patients with APL who had relapsed from or become refractory to all-trans retinoic acid (ATRA) and conventional chemotherapy in a prospective study.

Recently, arsenic trioxide (ATO) has been proved to induce complete remission (CR) at a high rate in patients with acute promyelocytic leukemia (APL). We prospectively investigated the safety and efficacy of ATO therapy in patients with relapsed and refractory APL and examined the duration of CR and the postremission therapies. Initially, 0.15 mg/kg ATO was administered until bone marrow remission to a maximum of 60 days. After the patient achieved CR, 1 additional ATO course at the same dosage was administered for 25 days. Of 34 patients, 31 (91%) achieved CR. PML-RAR3 messenger RNA was not detected in the bone marrow of 18 (72%) of the 25 patients evaluated by reverse transcriptase-polymerase chain reaction analysis. At a median follow-up of 30 months, the estimated 2-year overall survival rate was 56%, and the estimated 2-year event-free survival rate was 17%. During the ATO therapy, QTc prolongation was observed in most cases. Fifteen patients developed ventricular tachycardia, and 1 of them showed torsades de pointes. Other adverse events were nausea, water retention, APL differentiation syndrome, skin eruption, liver dysfunction, and peripheral neuropathy, all of which were quite tolerable. ATO therapy was remarkably effective for relapsed APL; however, postremission therapies were necessary to maintain a durable remission.

This study demonstrates that ATO is metabolized when administered intravenously to APL patients and methylated metabolites are promptly eliminated from the blood and excreted into urine after completion of administration, indicating no measurable accumulation of ATO in the blood.

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