Single-agent arsenic trioxide in the treatment of newly diagnosed acute promyelocytic leukemia: durable remissions with minimal toxicity

Arsenic trioxide, as a single agent, has proven efficacy in inducing molecular remission in patients with acute promyelocytic leukemia (APL). There is limited long-term outcome data with single-agent As2O3 in the management of newly diagnosed cases of APL. Between January 1998 to December 2004, 72 newly diagnosed cases of APL were treated with a regimen of single-agent As2O3 at our center. Complete hematologic remission was achieved in 86.1%. At a median follow-up of 25 months (range: 8-92 months), the 3-year Kaplan-Meier estimate of EFS, DFS, and OS was 74.87% +/- 5.6%, 87.21% +/- 4.93%, and 86.11% +/- 4.08%, respectively. Patients presenting with a white blood cell (WBC) count lower than 5 x 10(9)/L and a platelet count higher than 20 x 10(9)/L at diagnosis (n = 22 [30.6%]) have an excellent prognosis with this regimen (EFS, OS, and DFS of 100%). The toxicity profile, in the majority, was mild and reversible. After remission induction, this regimen was administered on an outpatient basis. Single-agent As2O3, as used in this series, in the management of newly diagnosed cases of APL, is associated with responses comparable with conventional chemotherapy regimens. Additionally, this regimen has minimal toxicity and can be administered on an outpatient basis after remission induction.     

Tetra-arsenic tetra-sulfide for the treatment of acute promyelocytic leukemia: a pilot report

In the past 6 years, we treated 129 patients who had acute promyelocytic leukemia (APL) with a new arsenic agent, oral tetra-arsenic tetra-sulfide (As(4)S(4)). Nineteen of the patients had newly diagnosed APL, 7 had first relapse, and 103 had hematologic complete remission (HCR). HCR was achieved in all patients with newly diagnosed APL and in all those with hematologic relapse. Of 16 patients with newly diagnosed disease and available cytogenetic and molecular analyses, 14 had cytogenetic and molecular complete remission (CR). Cytogenetic and molecular CR was also obtained in 5 of the 7 patients with hematologic relapse. In the HCR group, 35 of 44 patients positive for PML-RARalpha at baseline became negative. In the newly diagnosed group, estimated disease-free survival (DFS) rates for 1 and 3 years were 86.1% and 76.6%, respectively, with a median follow-up time of 13.5 months (range, 2-40 months). In the HCR group, DFS rates for 1 and 6 years were 96.7% and 87.4%, respectively, with a median follow-up of 23 months (range, 2-71 months). Treatment with As(4)S(4) was well tolerated, with only moderate side effects, including asymptomatic prolongation of corrected QT interval, transient elevation in liver enzyme levels, rash, and mild gastrointestinal discomfort; neither myelosuppression nor appreciable long-term side effects occurred. Degeneration or apoptosis of APL promyelocytes was observed during As(4)S(4) therapy. Pharmacokinetic studies showed that the agent was absorbed rapidly. Most urinary arsenic excretion occurred within the first 24 hours. Both blood and urinary arsenic levels declined after discontinuation of As(4)S(4). Our results show, for the first time, that As(4)S(4) treatment alone is highly effective and safe in both remission induction and maintenance therapy in patients with APL, regardless of disease stage.     

All-trans retinoic acid and chemotherapy in the treatment of acute promyelocytic leukemia

All-trans retinoic acid (ATRA) can induce complete remission (CR) in most patients with acute promyelocytic leukemia (APL) through in vivo differentiation of APL-blasts. However, it cannot eliminate the leukemic clone and must be used in combination with anthracycline-based chemotherapy. Experience accumulated over the last 10 years has clearly shown that the combination of ATRA and chemotherapy gave better survival than chemotherapy alone in newly diagnosed APL because of fewer relapses and a slightly higher CR rate. It is also strongly suggested that maintenance treatment with ATRA, and possibly with low-dose chemotherapy, can further reduce the incidence of relapse. Overall, more than 90% of patients with newly diagnosed APL can achieved CR, and about 75% can be cured by the combination of ATRA and chemotherapy. ATRA syndrome remains the major side effect of ATRA treatment, which should be prevented by addition of chemotherapy and/or dexamethasone in case of increasing white blood cell (WBC) counts. Current issues in the treatment of newly diagnosed APL include the role of early addition of chemotherapy to ATRA, whether or not ara-C is useful in combination with anthracycline, and a possible interest of arsenic trioxide during consolidation in patients remaining at relatively high risk of relapse.     

All-trans retinoic acid in acute promyelocytic leukemia: long-term outcome and prognostic factor analysis from the North American Intergroup protocol

We previously reported a benefit for all-trans retinoic acid (ATRA) in both induction and maintenance therapy in patients with acute promyelocytic leukemia (APL). To determine the durability of this benefit and identify important prognostic factors, long-term follow-up of the North American Intergroup APL trial is reported. A total of 350 patients with newly diagnosed APL were randomized to either daunorubicin and cytarabine (DA) or ATRA for induction and then either ATRA maintenance or observation following consolidation chemotherapy. The complete remission (CR) rates were not significantly different between the ATRA and DA groups (70% and 73%, respectively). However, the 5-year disease-free survival (DFS) and overall survival (OS) were longer with ATRA than with DA for induction (69% vs 29% and 69% vs 45%, respectively). Based on both induction and maintenance randomizations, the 5-year DFS was 16% for patients randomized to DA and observation, 47% for DA and ATRA, 55% for ATRA and observation, and 74% for ATRA and ATRA. There was no advantage of either induction regimen among any subgroups when CR alone was considered. However, female sex, classical M3 morphology (vs the microgranular variant [M3v]), and treatment-white blood cell count (WBC) interaction (ATRA/WBC below 2 x 10(9)/L [2000/microL] best, DA/WBC above 2 x 10(9)/L worst) were each significantly associated with improved DFS (P <.05). Treatment with ATRA, WBC below 2 x 10(9)/L, and absence of bleeding disorder were each significantly associated with improved OS. Age more than 15 years, female sex, and treatment-morphology interaction (DA/M3v worst, ATRA best regardless of morphology) were each significantly associated with improved DFS based on maintenance randomization. The improvement in outcome with ATRA in APL was maintained with long-term follow-up.     

Effect of arsenic trioxide on the treatment of children with newly diagnosed acute promyelocytic leukemia in China

To explore the efficacy of treatment for childhood acute promyelocytic leukemia (APL) with a combination of all-trans-retinoic acid (ATRA) and arsenic trioxide (As₂O₃) for remission induction, we reviewed the clinical course and outcome of 37 children with APL from January 1999 to December 2003. Among the 37 children (≤14 years) with newly diagnosed APL, we applied treatments that consisted of ATRA alone or in combination with As₂O₃ in induction followed by consolidation and maintenance treatment. Overall, 35 (94.6%) of 37 children achieved complete remission (CR). Two patients died of intracerebral hemorrhage on days 1 and 2. The 5-year estimates of event-free survival (EFS), disease-free survival (DFS), and overall survival (OS) rates for the 37 patients were 79.2, 83.7, and 91.5%, respectively. There were 27 patients with white blood cell (WBC) count lower than 10 × 10⁹/L. In 27 patients with a WBC count <10 × 10⁹/L, 17 patients (group-I) were treated with ATRA alone and 10 patients (group-II) were treated with ATRA which was switched to As₂O₃ due to the side effects of ATRA. Although the 5-year estimate of DFS between group-I and group-II showed no significant difference (P = 0.108), the DFS rate improved by 25% in group-II. Our results suggest that the combination of As₂O₃ and ATRA might decrease the relapse rate compared with ATRA alone in induction therapy for childhood APL, at least in those with a WBC count less than 10 × 10⁹/L.     

Successful treatment of relapsed and refractory acute promyelocytic leukemia with arsenic trioxide (As2O3)

It has been shown that arsenic trioxide (As2O3) may induce hematologic remissions in patients with acute promyelocytic leukemia (APL) refractory to all-trans retinoic acid (ATRA). We reported on a patient with ATRA and drug-resistant APL that was successfully treated with As2O3. The patient had been given a diagnosis of typical APL and was treated with ATRA and chemotherapy for 12 months. He achieved complete remission (CR), but leukemia relapsed with 43% APL cells in the bone marrow in the 16th month of treatment. ATRA and cytarabine plus daunorubicin were administered; however, the APL cells in the bone marrow increased to 97.2%. As2O3 was initiated intravenously, and bone marrow showed a decrease of APL cells (6.7%) and a partial differentiation after 9 days. The patient received idarubicin (IDA) and steroid pulse because of the development of ATRA-like syndrome, and achieved CR 37 days after the initiation of As2O3. He received an additional 2 courses of As2O3 with IDA, and is in CR. These results demonstrated the therapeutic efficacy of As2O3 in treating ATRA and drug-resistant APL.     

Oral administration of arsenic trioxide induced molecular remission in relapsed acute promyelocytic leukemia

I report on a 21-year-old man with acute promyelocytic leukemia (APL) which relapsed after a therapeutic regimen consisting of tretinoin, daunorubicin, enocitabine, mitoxantrone, and cytarabine. The patient also had severe mental retardation caused by a congenital central nervous system malformation. Administration of arsenic trioxide (As2O3) is indicated for patients with APL, however, daily intravenous infusion of As2O3 presented problems because of the patient's violent resistance to venous access. Accordingly, 10mg of an oral solution of As2O3 was given once daily for 70 days. No adverse events were observed with the exception of transient hyperleukocytosis and fever. The patient achieved molecular remission 103 days after the start of oral As2O3, and remains in remission after an additional 2 courses of oral As2O3 as consolidation chemotherapy. Oral As2O3 may be useful in the treatment of relapsed APL as an alternative to intravenous As2O3.     

Acute promyelocytic leukemia: recent advances in therapy and molecular basis of response to arsenic therapies

PURPOSE OF REVIEW: While arsenic has long been known as a poison and environmental carcinogen, its dramatic effect in the treatment of acute promyelocytic leukemia (APL) has made its mechanism of action a topic of intense interest. This paper reviews recent findings that reveal why a traditional poison has become a magical potion for a major type of APL, which is characterized by a balanced chromosomal translocation t(15;17). RECENT FINDINGS: Daily IV infusion of arsenic trioxide (As2O3; ATO) for 30 to 40 days can lead to complete remission in about 85% of patients with newly diagnosed or relapsed APL. Oral preparations of ATO and tetra-arsenic tetra-sulfide (As4S4) seem to be as effective as parenteral ATO, with similar toxicity profiles. The combination of all-trans retinoic acid and ATO in patients with newly diagnosed APL has yielded more durable remission than monotherapy. The mechanism of arsenic cytotoxicity is thought to involve posttranslational modification followed by degradation of the PML-retinoic acid receptor-alpha (PML-RARalpha) fusion protein; targeting of PML to nuclear bodies with restoration of its physiologic functions; and production of reactive oxygen species (ROS) by NADPH oxidase in leukemic cells or collapse of the mitochondrial transmembrane potential. The understanding of arsenic cytotoxicity has stimulated modifications that promise to improve efficacy, such as interfering with ROS scavenging or boosting of ROS production to enhance the cytotoxicity, and adding cAMP or interferons to ATO regimens. SUMMARY: Recent advances in the clinical use of arsenic, the mechanism of arsenic-mediated cytotoxicity, and modulations of ATO to increase its efficacy and expand its clinical spectrum are reviewed.     

Arsenic trioxide in the treatment of newly diagnosed acute promyelocytic leukemia: a single center experience

Arsenic trioxide (As(2)O(3)) has been found effective in the treatment in the treatment of acute promyelocytic leukemia (APML). Most studies with As(2)O(3) involve patients with APML who have relapsed following standard therapy. Between January 1998 and July 2000, 14 patients were recruited for an ongoing trial of As(2)O(3) in the treatment of newly diagnosed APML. Arsenic trioxide was administered at a dose of 10 mg/day until complete remission (CR) was achieved. Afterward, a consolidation course and a maintenance schedule consisting of As(2)O(3) as a single agent were administered over 6 months. There were 3 early deaths related to intra-cerebral hemorrhage: two on day 3 and one on day 4. Of the 11 evaluable patients, one died on day 21 secondary to uncontrolled sepsis, while the remaining 10 (91%) have attained CR. The average time to CR was 52.3 days (range: 34-70 days). One patient developed an isolated central nervous system (CNS) relapse and subsequently went into a second CR following therapy with triple intrathecal chemotherapy, cranial irradiation, and an additional 4-week course of systemic As(2)O(3). This patient, as well as the remaining nine, has continued to remain in CR at a median follow up of 15 months (range: 2-33 months). Eight out of 10 patients achieved molecular remission at variable periods during their consolidation and maintenance schedules. One patient developed an ATRA syndrome and was administered daunorubicin (40 mg/day) for 2 days. The side effects with this therapy were minimal and did not require cessation of therapy in any patient. There was no significant hepatic toxicity. In our experience, arsenic trioxide is effective in inducing and maintaining remission in patients with APML with minimal side effects. The optimal regimen and total dose required need to be defined.     

A randomized comparison of all transretinoic acid (ATRA) followed by chemotherapy and ATRA plus chemotherapy and the role of maintenance therapy in newly diagnosed acute promyelocytic leukemia. The European APL Group.

All transretinoic acid (ATRA) followed by daunorubicin (DNR)-AraC chemotherapy (CT) has improved the outcome of acute promyelocytic leukemia (APL) by comparison to CT alone. In a randomized trial, (1) we compared 2 induction schedules (ATRA followed by CT [ATRA-->CT] and ATRA plus CT [ATRA+CT, with CT added on day 3 of ATRA treatment]) and (2) we assessed the role of maintenance treatment. Four hundred thirteen patients CT and ATRA+CT (initially randomized patients); patients with a WBC count greater than (high WBC count group, n = 163) and patients 66 to 75 years of age with a WBC count greater than 5,000/microL (elderly group, n = 42) were not initially randomized and received ATRA+CT from day 1 and ATRA -->CT, respectively. All patients achieving CR received 2 additional DNR-AraC courses (only 1 in patients 66 to 75 years of age) and were then randomized for maintenance between no treatment, intermittent ATRA (15 days every 3 months) for 2 years, continuous low-dose CT (6 mercaptopurine + methotrexate) for 2 years, or both, using a 2-by-2 factorial design. Overall, 381 (92%) of the patients achieved complete remission (CR), 31 (7%) suffered an early death, and only 1 patient had leukemic resistance. ATRA syndrome occurred in 64 patients (15%) and was fatal in 5 cases. The CR rate was similar in all induction treatment groups. Event-free survival (EFS) was significantly lower in the high WBC group (P =.0002) and close to significance in the elderly group (P =.086) as compared with initially randomized patients. Relapse at 2 years was estimated at 6% in the ATRA+CT group, versus 16% in the ATRA-->CT group (P =.04, relative risk [RR] =.41). EFS at 2 years was estimated at 84% in the ATRA+CT group, versus 77% in the ATRA-->CT group (P =.1, RR =.62). Two hundred eighty-nine patients were randomized for maintenance. The 2-year relapse rate was 11% in patients randomized to continuous maintenance CT and 27% in patients randomized to no CT (P =.0002) and 13% in patients randomized to intermittent ATRA and 25% in patients randomized to no ATRA (P =.02). An additive effect of continuous maintenance CT and intermittent ATRA was seen, and only 6 of the 74 patients who received both maintenance treatments had relapsed. Overall survival was improved in patients who received maintenance CT (P =.01), and there was a trend for better survival in patients who received maintenance ATRA (P =.22). Our findings strongly suggest that early addition of chemotherapy to ATRA and maintenance therapy combining continuous CT and intermittent ATRA can reduce the incidence of relapse in APL. This effect already translates into significantly better survival for maintenance treatment with continuous CT.     

New advances in the treatment of acute promyelocytic leukemia

OBJECTIVE: Describe the treatment options of newly diagnosed and relapsed APL. INDUCTION: The fusion PML/RAR gene provided the rationale for using all-trans retinoic acid (ATRA) as differentiation therapy. The standard approach is antracycline + ATRA and no ARA-C. CONSOLIDATION: Anthracycline based chemotherapy, no high dose ARA-C and perhaps no ARA-C. Maintenance seems to be important. Cure with ATRA + chemotherapy increased to 75% from 35% with chemotherapy alone. POOR PROGNOSIS FACTORS: WBC >10,000, age >55, platelets <40,000 and CD 56 expression. Achieving and maintaining a molecular remission (MCR) i.e. RT-PCR (-) for PML/RAR alpha expression, is the best predictor for cure. Conversion to PCR (+) will eventually result in relapse. PCR monitoring in the first 2 years and intervention during molecular relapse would be safer than treatment in clinical relapse. Molecular relapses have been treated successfully by ATRA plus BMT. Arsenic trioxide (ATO) or gentuzumab (mylotarg) are also being studied. RELAPSE (INDUCTION): Patients after ATRA in first CR are less likely to respond to ATRA reinduction regardless of the time off ATRA and rarely achieve a molecular remission. Single-agent ATO induced in 52 relapsed patients CR of 87% (75% MCR) with low toxicity and no treatment related deaths (U.S. pivotal trial), confirmed in a NCI trial. Induction of relapsing patients with single agent ATO is preferable than ATRA + chemotherapy because the high molecular remission and lower toxicity. RELAPSE (POST REMISSION): No standard approach and the role of chemotherapy is unknown. ATO alone: in the pivotal trial, 9/21 patients had long remissions without other therapy. BMT: Not indicated in 1st MCR. In young patients auto BMT with PCR (-) harvests could be done in subsequent CR. Allo BMT has a higher death rate without overall better results. In the pivotal trial 12 patients were transplanted in CR after ATO alone (9 allo BMT) and 11 still without disease. Possibly allo BMT is safer after a less toxic ATO induction. OTHER: ATO plus ATRA +/- AntiCD33 conjugated with toxin (gentuzumab) or 131I; Synthetic retinoid (Am80); histone deacetylase inhibitors; oral tetra-arsenic tetra-sulfide and various combinations.     

Acute promyelocytic leukemia: from highly fatal to highly curable

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia. Morphologically, it is identified as the M3 subtype of acute myeloid leukemia by the French-American-British classification and cytogenetically is characterized by a balanced reciprocal translocation between chromosomes 15 and 17, which results in the fusion between promyelocytic leukemia (PML) gene and retinoic acid receptor alpha (RARalpha). It seems that the disease is the most malignant form of acute leukemia with a severe bleeding tendency and a fatal course of only weeks. Chemotherapy (CT; daunorubicin, idarubicin and cytosine arabinoside) was the front-line treatment of APL with a complete remission (CR) rate of 75% to 80% in newly diagnosed patients. Despite all these progresses, the median duration of remission ranged from 11 to 25 months and only 35% to 45% of the patients could be cured by CT. Since the introduction of all-trans retinoic acid (ATRA) in the treatment and optimization of the ATRA-based regimens, the CR rate was raised up to 90% to 95% and 5-year disease free survival (DFS) to 74%. The use of arsenic trioxide (ATO) since early 1990s further improved the clinical outcome of refractory or relapsed as well as newly diagnosed APL. In this article, we review the history of introduction of ATRA and ATO into clinical use and the mechanistic studies in understanding this model of cancer targeted therapy.     

Four years' experience with the treatment of all-trans retinoic acid in acute promyelocytic leukemia

A retrospective analysis was done on 43 patients with acute promyelocytic leukemia (APL) at our hospital from June 1987 to August 1992. All-trans retinoic acid was used to induce these patients to differentiation. In the early period of induction there were risks of severe hemorrhage, which was the main cause of early death. Treatments combined with platelets and heparin or aminomethylbenzoic (PAMBA) were given to patients with abnormal coagulation. As a result only 4 out of 43 patients died of intracranial bleeding at 4–12 days when their white blood cell (WBC) counts peaked. The combination of retinoic acid (RA) and HA chemotherapy could reduce hyperleukocytosis during the RA induction course. None of 7 patients died at early stage with this treatment combination. Our studies showed that it could predict the onset of remission at early stage through observations on the successive changes of karyotypes and morphology of the bone marrow and peripheral blood cells. Our studies also showed that the growth of CFU-F could be inhibited by RA. We think that it may play a role in the RA-induced differentiation. In 4 years of follow-up the overall leukemia-free survival (LFS) was 80% with a relapse rate of 45%. Thirty-five patients out of 43 cases were still alive in remission, and one was alive in relapse. All 11 out of 43 patients relapsed within 3 years, but the relapses occurred later, after 3 years duration of remission (P < .01). Retinoic acid failed to induce 5 patients who relapsed with the continuation treatment of RA and chemotherapy alternatively. In order to overcome the resistance to RA, the continuation treatment of simple chemotherapy had been administered following CR. Two cases achieved remission in this way. The difference of resistant events to RA reached significance between these 2 groups of different continuation treatment.     

Treatment of newly diagnosed acute promyelocytic leukemia (APL): a comparison of French-Belgian-Swiss and PETHEMA results

All-trans retinoic acid (ATRA) plus anthracycline chemotherapy is the reference treatment of newly diagnosed acute promyelocytic leukemia (APL), whereas the role of cytosine arabinoside (AraC) remains disputed. We performed a joint analysis of patients younger than 65 years included in Programa para el Estudio de la Terapéutica en Hemopatía Maligna (PETHEMA) LPA 99 trial, where patients received no AraC in addition to ATRA, high cumulative dose idarubicin, and mitoxantrone, and APL 2000 trial, where patients received AraC in addition to ATRA and lower cumulative dose daunorubicin. In patients with white blood cell (WBC) count less than 10 x 10(9)/L, complete remission (CR) rates were similar, but 3-year cumulative incidence of relapse (CIR) was significantly lower in LPA 99 trial: 4.2% versus 14.3% (P = .03), although 3-year survival was similar in both trials. This suggested that AraC is not required in APL with WBC count less than 10 x 10(9)/L, at least in trials with high-dose anthracycline and maintenance treatment. In patients with WBC of 10 x 10(9)/L or more, however, the CR rate (95.1% vs 83.6% P = .018) and 3-year survival (91.5% vs 80.8%, P = .026) were significantly higher in APL 2000 trial, and there was a trend for lower 3-year CIR (9.9% vs 18.5%, P = .12), suggesting a beneficial role for AraC in those patients.     

Clinical characteristics,prognostic factors and multidrug-resistance related protein expression in 36 adult patients with acute promyelocytic leukemia

We report on a single-center experience about the characteristics and outcome of 36 acute promyelocytic leukemia (APL) patients observed at our Department of Hematology between 1990 and 2002. The expression, of multidrug-resistance (MDR) associated proteins (PGP, LRP, MRP1) was also analyzed. There were 12 males and 24 females (median age 37 yr), 89% (32 of 36) with classic morphology, and 11% (four of 36) with a microgranular variant. Risk class (according to GIMEMA/PETHEMA): 25% (nine of 36) high risk (HR), 53% (nineteen of 36) intermediate risk (IR), 22% (eight of 36) low risk (LR). PGP, LRP, and MRP1 expression at onset and at first relapse was low. CD33 antigen expression was high in all cases. The patients were treated according to GIMEMA protocols (LAP0389 and AIDA) including ATRA in induction in 75% (27 of 36) of cases and 94% (34 of 36) achieved a complete remission (CR) after induction therapy while 6% (two of 36) died early (DDI) of hemorrhage. Outcome: 71% (24 of 34) of evaluable patients remain in CR at a median follow-up of 57 months (range 4-158 months) while 29% (10 of 34) relapsed at a median time of 12 months (range 8-43 months) and, of them, eight of 10 died early. The majority of patients that relapsed were in high-risk group. The overall survival (OS) of the whole population at 32 months was 66% and the DFS at 42 months was 62%. A statistically significant difference in terms of DFS was observed between HR and IR/LR patients (P = 0.04 by log-rank). DFS was not affected by age, sex, Hb levels, karyotype, and BCR isoform. At conclusion, our data confirm that despite the high rate of success with ATRA plus chemotherapy as induction (more than 90% of CR), about 30% of APL patients have a relapse (without a long-lasting second remission) and underline the importance of patient stratification in distinct risk groups at diagnosis in order to better adapt the type and intensity of treatment (risk-adapted therapy). Taking into account the high expression of CD33 and the low expression of MDR proteins in APL, new and investigational approaches like gemtuzumab-ozogamicin, with or without ATRA and other new drugs, should be strongly considered expecially in HR APL.     

Induction therapy with idarubicin alone significantly influences event-free survival duration in patients with newly diagnosed hypergranular acute promyelocytic leukemia: final results of the GIMEMA randomized study LAP 0389 with 7 years of minimal follow-up

Shortly before the all-trans retinoic acid (ATRA) era, the GIMEMA cooperative group initiated a randomized study comparing idarubicin (IDA) alone with IDA plus arabinosylcytosine (Ara-C) as induction treatment in patients with newly diagnosed hypergranular acute promyelocytic leukemia (APL). Of the 257 patients evaluable for induction treatment, 131 were randomized to receive IDA alone (arm A) and 126 to receive IDA + Ara-C (arm B). Treatment in arm A consisted of 10 mg/m(2) IDA daily for 6 consecutive days, whereas in arm B it consisted of 12 mg/m(2) IDA daily for 4 days combined with 200 mg/m(2) Ara-C daily in continuous infusion for 7 days. Once in complete remission (CR), patients received 3 consolidation courses of standard chemotherapy, and those still in CR at the end of the consolidation were randomized to receive or not receive 1 mg/kg 6-mercaptopurine daily and intramuscular injections of 0.25 mg/kg methotrexate weekly for 2 years. Overall, 100 (76.3%) patients in arm A and 84 (66.6%) patients in arm B achieved CR (P = NS). Event-free survival (EFS) rates were 35% and 23% for patients in arm A and arm B, respectively (P =.0352). Multivariate analysis revealed that EFS was favorably influenced by induction treatment with IDA alone (P =.0352) and unfavorably influenced by white blood cell (WBC) counts greater than 3000/microL (P =.0001) and increasing age (P =.0251). These results indicate that anthracycline monochemotherapy with IDA favorably influences the EFS of patients with newly diagnosed hypergranular APL.