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

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 ≥10 × 10³/μl. 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. Cancer 1994; 73:2946–52.