Retinoic acid in the treatment of acute promyelocytic leukemia: inefficacy of the 13-cis isomer and induction of complete remission by the all-trans isomer complicated by thromboembolic events.

The clinical course of three patients with acute promyelocytic leukemia receiving all-trans retinoic acid (ATRA) as a single agent is reported. The first two patients were in first and second relapse of their leukemia that had occurred despite maintenance treatment with 13-cis retinoic acid after chemotherapy-induced complete remission (CR). A switch to ATRA was followed by achievement of a CR in two patients. The third patient received ATRA as first-line therapy. Two patients experienced thromboembolic complications during the phase of ATRA-induced leukocytosis. One of them died of pulmonary embolism on day 16 of treatment. The two responding patients who did not receive consolidation chemotherapy relapsed after 6 and 9 months, respectively. Increase of the ATRA dose failed to induce a new remission.