Use of all-trans retinoic acid plus arsenic trioxide as an alternative to chemotherapy in untreated acute promyelocytic leukemia

We examined whether combining all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) might be an alternative to ATRA plus chemotherapy in untreated acute promyelocytic leukemia (APL). Twenty-five low-risk patients (white blood cell [WBC] count less than 10 × 10⁹/L [10 000/μL]) received ATRA (45 mg/m² daily) and ATO (0.15 mg/kg daily, beginning day 10 of ATRA), and in complete remission (CR) received ATO plus ATRA, without chemotherapy, unless they were reverse transcriptase-polymerase chain reaction (RT-PCR)-positive 3 months from CR date or had molecular relapse. Nineteen high-risk patients were treated identically, but received chemotherapy, generally 9 mg/m² gemtuzumab ozogamycin (GO) on day 1 of induction. The CR rate was 39 of 44 (24 of 25 in low-risk, 15 of 19 in high-risk). Disease recurred at 9, 9, and 15 months, respectively, in 3 high-risk patients. The median follow-up time from CR date in the 36 patients alive in first CR is 16 months (15 months in low-risk, 20 months in high-risk), with 9 patients followed for at least 24 months. Each of the 36 patients was PCR-negative at last follow-up. Thus, none of the low-risk patients has received chemotherapy, and only 3 high-risk patients (the 3 with relapsed disease) have received chemotherapy past induction. ATRA plus ATO may serve as an alternative to chemotherapy in low-risk untreated APL (eg, in older patients) and, when combined with GO, may improve outcome in high-risk patients.