All-trans retinoic acid followed by chemotherapy for salvage of refractory or relapsed acute promyelocytic leukemia

Abstract

Background: All-trans retinoic acid (ATRA) is effective in the treatment of relapsed or refractory acute promyelocytic leukemia (APL), but relapse is the rule if response is unmaintained.

Methods: Seventeen patients with APL were salvaged with ATRA at a dosage of 50 mg/m2/day for 3 months or until complete remission (CR) was achieved; idarubicin (12 mg/m2/day for 4 days) was added if blast plus promyelocyte count either was or reached > or = 10 x 10(3)/microliters. After CR was achieved, patients received three courses of idarubicin (12 mg/m2 daily for 3 days) followed by three courses of mitoxantrone (5 mg/m2 daily for 3 days) and etoposide (250 mg/m2 daily for 3 days). Maintenance was with 6-mercaptopurine and methotrexate.

Results: A CR was achieved in 14 patients (82%), the disease was refractory in 2 patients, and one patient died during induction. Three patients underwent allogeneic bone marrow transplant during CR. After a median follow-up of 26 weeks, six patients remain in CR. Median CR duration is 40 weeks (range 8-56+). Patients treated with ATRA plus chemotherapy in first salvage, when compared to a historic control group treated with chemotherapy alone, had a significantly better CR rate (87% vs. 57%; P = 0.04) and a lower induction death rate (7% vs. 29%; P = 0.08), resulting in longer median survival (26 vs. 17 weeks; P = 0.13). Four patients developed the "retinoic acid syndrome", which was fatal in one case. Three patients developed thrombotic events.

Conclusions: ATRA followed by chemotherapy is effective treatment for patients with APL who relapse after conventional therapy, and it may be superior to chemotherapy alone.