Arsenic trioxide: new preparation. Acute promyelocytic leukaemia: encouraging results but persistent doubts

(1) Acute promyelocytic leukaemia is a rare disease. There is a high remission rate after combination treatment with tretinoin and anthracycline, but there is no established treatment for refractory or relapsed disease. Further treatment with tretinoin, combined with intensive cytotoxic chemotherapy, seems to give the best results in patients who qualify for this treatment, but assessment is limited. (2) Arsenic trioxide has now been approved for induction of remission and consolidation in patients with refractory or relapsed acute promyelocytic leukaemia. (3) The clinical evaluation dossier that supported the application contains data from two non comparative trials including 12 and 40 patients. A complete haematological response was obtained in 45 (87%) of the 52 patients, and the survival rate among patients in first relapse was 77% after a median follow-up of two years. These results are similar to those previously obtained with tretinoin plus intensive cytotoxic chemotherapy. (4) All the patients treated with arsenic trioxide experienced adverse events. This was to be expected given the acute and chronic toxicity of arsenicals. Most events included fatigue, gastrointestinal disturbances, peripheral neuropathies, prolongation of the QT interval; and biochemical disturbances (hypokalaemia, hyperglycaemia, elevated transaminase activity). (5) Like tretinoin, arsenic trioxide can provoke a potentially severe leukocyte activation syndrome. (6) In practice, these encouraging data justify further assessment of arsenic trioxide. This drug is already an option for patients with refractory or relapsed disease who cannot receive tretinoin plus intensive chemotherapy.