Results of a randomized trial comparing idarubicin and cytosine arabinoside with daunorubicin and cytosine arabinoside in adult patients with newly diagnosed acute myelogenous leukemia

4'-Demethoxydaunorubicin (idarubicin [IDR]) is a new anthracycline that differs from its parent compound by the deletion of a methoxy group at position 4 of the chromophore ring. This minor structural modification results in a more lipophilic compound with a unique metabolite that has a prolonged plasma half-life as well as in vitro and in vivo antileukemia activity. To determine its activity in acute myelogenous leukemia (AML), 130 consecutive adult patients between the ages of 16 and 60 with newly diagnosed disease were randomized in a single institution study to receive either IDR in combination with cytosine arabinoside (Ara-C) or standard therapy with daunorubicin (DNR) and Ara-C. The trial was analyzed using the O'Brien-Fleming multiple testing design that allowed for periodic inspection of the data at specific patient accession points. After accrual of 60 patients per arm, analysis showed that patients who received IDR/Ara-C had a superior response compared with those who received standard therapy: 48 of 60 patients (80%) achieved complete remission on the former arm compared with 35 of 60 patients on the latter (58%, P = .005). Logistic regression analysis of factors associated with complete response indicated that treatment with IDR/Ara-C offered a significant advantage to patients who presented with a high initial white blood cell count compared with treatment with DNR/Ara-C. The degree of marrow aplasia was approximately the same on each arm as was nonhematologic toxicity. Overall survival for patients on the IDR/Ara-C arm was 19.5 months compared with 13.5 months on the DNR/Ara-C arm (P = .025) at a median follow-up of 2.5 years. We conclude that IDR/Ara-C can effectively replace standard therapy with DNR/Ara-C in adult patients less than age 60 with newly diagnosed AML.     

Sequential mitoxantrone,daunorubicin, and cytosine arabinoside for patients with newly diagnosed acute myelocytic leukemia

Mitoxantrone (M) is a synthetic aminoanthraquinone with anti-leukemic activity in patients with daunorubicin (D) resistant acute leukemia. The Cancer and Leukemia Group B (CALGB) has undertaken a limited access pilot study in which M, 12 mg/m², over 30 min, daily for 3 days, and cytosine arabinoside (Ara-C), 100 mg/m²/day by constant infusion for 7 days were used for the induction of newly diagnosed patients with AML. Responding patients were consolidated with daunorubicin, 45 mg/m²/day for 3 days, and 7 days of Ara-C. After a second consolidation identical to induction, no further therapy was given. Twenty-nine patients with a median age of 50 years (range 18–72) were entered in the study; 18 were males and 11 females. Twenty-four (83%) patients achieved CR, 1 patient achieved a PR, and 4 died in induction from leukemia-related causes. Two patients died in CR from consolidation-related neutropenic sepsis and two additional patients died in CR. Of 24 patients, 7 remain disease-free at a median follow-up interval of 8 years. The regimen is active and well tolerated. The duration of disease-free survival in responding patients is consistent with that seen in similar regimens using intensification chemotherapy without prolonged maintenance. Am. J. Hematol. 56:214–218, 1997. © 1997 Wiley-Liss, Inc.     

Sequential standard dose mitoxantrone and cytosine arabinoside for newly diagnosed adult acute myeloblastic leukemia.

Twenty one adult patients with previously untreated acute myeloblastic leukemia (AML) were treated with sequential mitoxantrone and standard dose cytosine arabinoside remission induction therapy. The median age was 33 years (range 17-56 years). Complete remission (CR) was achieved in 80% (17/21 cases) and 76% (16/21 cases) achieved CR after one course of induction therapy. The median duration of disease free survival was 9 months with an actuarial disease free survival of 22% at 43 months. The non-hematological toxicity was acceptable. We conclude that sequential mitoxantrone and cytosine arabinoside combination therapy is an effective antileukemic regimen which produces high CR rates in previously untreated adult patients with AML.     

A randomized investigation of high-dose versus standard-dose cytosine arabinoside with daunorubicin in patients with previously untreated acute myeloid leukemia: a Southwest Oncology Group study

Interest in high-dose cytarabine (HDAC) for both induction and postremission therapy for acute myeloid leukemia (AML) prompted the Southwest Oncology Group (SWOG) to initiate a randomized trial comparing HDAC with standard-dose cytarabine (SDAC) for remission induction of previously untreated AML and to compare high-dose treatment versus conventional doses for consolidation therapy. Patients less than 65 years of age with de novo or secondary AML were randomized for induction between SDAC 200 mg/ m2/d for 7 days by continuous infusion or HDAC at 2 g/ m2 intravenously every 12 hours for 12 doses; both groups received daunorubicin (DNR) at 45 mg/m2/d intravenously for 3 days. Complete responders to SDAC were randomized to receive either two additional courses of SDAC plus DNR or one course of HDAC plus DNR. Complete responders to HDAC were nonrandomly assigned to receive one additional course of HDAC plus DNR. Of patients randomized between SDAC (n = 493) and HDAC (n = 172) induction, 361 achieved complete remission (CR). The CR rate was slightly poorer with HDAC: 55% versus 58% with SDAC for patients aged less than 50, and 45% (HDAC) versus 53% (SDAC) for patients aged 50 to 64 (age-adjusted one-tailed P = .96). With a median follow-up time of 51 months, survival was not significantly better with HDAC (P = .41); the estimated survival rate at 4 years was 32% (HDAC) versus 22% (SDAC) for those aged less than 50, and 13% (HDAC) versus 11% (SDAC) for those aged 50 to 64. However, relapse-free survival was somewhat better following HDAC Induction (P = .049): 33% (HDAC) versus 21% (SDAC) at 4 years for those aged less than 50, and 21% (HDAC) versus 9% (SDAC) for those aged 50 to 64. Induction with HDAC was associated with a significantly increased risk of fatal (P = .0033) and neurologic (P < .0001) toxicity. Among patients who achieved CR with SDAC, survival and disease-free survival (DFS) following consolidation randomization were not significantly better with HDAC compared with SDAC (P = .77 and .46, respectively). Patients who received both HDAC induction and consolidation had the best postremission outcomes; however, the proportion of CR patients who did not go on to protocol consolidation therapy was more than twice as high after HDAC induction compared with SDAC. Induction therapy with HDAC plus DNR was associated with greater toxicity than SDAC plus DNR, but with no improvement in CR rate or survival. Following CR induction with SDAC, consolidation with HDAC increased toxicity but not survival or DFS. In a nonrandomized comparison, patients who received both HDAC induction and consolidation had superior survival and DFS compared with those who received SDAC induction with either SDAC or HDAC consolidation.     

Multicenter prospective study of interferon-alpha and conventional chemotherapy versus bone marrow transplantation for newly diagnosed patients with chronic myelogenous leukemia. Kouseisho Leukemia Study Group

We compared interferon-alpha (IFN-alpha therapy with bone marrow transplantation (BMT) after initial conventional chemotherapy in patients with chronic myelogenous leukemia (CML) in a multicenter prospective study. Ninety patients with Philadelphia chromosome-positive CML in chronic phase were enrolled between 1991 and 1994. Sixty-six of 89 evaluable patients received IFN-alpha after conventional chemotherapy with hydroxyurea or busulfan (IFN-alpha group). Twenty-three patients received allogeneic BMT (BMT group). Fifteen of them received transplants from HLA-identical family donors and 8 from HLA-matched unrelated donors. Forty-seven of 66 patients (71%) in the IFN-alpha group and 17 of 23 patients (74%) in the BMT group achieved complete hematologic response, and 12% in the IFN-alpha group and 13% in the BMT group achieved partial hematologic response. Complete cytogenetic response was induced in 5 (8%), partial cytogenetic response in 8 (12%), and minor cytogenetic response in 12 (18%) in the IFN-alpha group. At a median follow-up of 54 months (range, 30-76 months), in the IFN-alpha group, the predicted 6-year survival rate was 54.5% and the predicted 6-year rate of those remaining in chronic phase was 45.7%. Compared with patients with no cytogenetic response, the patients with some cytogenetic response after IFN-alpha treatment had significantly superior survival and duration of the chronic phase even after correction for the time to response using landmark analysis (P < .05). In the BMT group, the predicted 5-year survival rate was 93.3% for family-donor BMT and 21.9% for unrelated-donor BMT Acute graft-versus-host disease of grade III or IV was observed in 1 of 15 patients who received family-donor BMT and 3 of 8 patients who received unrelated donor BMT. Prior treatment with conventional cytotoxic drugs induced early hematologic response and did not reduce the effect of IFN-alpha on CML. Unrelated-donor transplantation should be offered to some patients according to patient age, HLA-matching status, time from diagnosis to BMT, and risk factors.     

Remission of rheumatoid arthritis with the successful treatment of acute myelogenous leukemia with cytosine arabinoside, daunorubicin, and m-AMSA

We describe 2 patients in whom a sustained remission of longstanding rheumatoid arthritis occurred with treatment for acute myelogenous leukemia (cytosine arabinoside, daunorubicin, and m-AMSA), even though both illnesses had been refractory to therapy with standard disease-modifying agents. These 2 patients represent the first successful treatment of rheumatoid disease using such an approach.     

A randomized trial comparing interferon-alpha with busulfan for newly diagnosed chronic myelogenous leukemia in chronic phase

A multicenter randomized study was conducted to compare the effect of interferon-alpha (IFN-alpha) with that of busulfan in newly diagnosed patients with chronic myelogenous leukemia (CML) in chronic phase. From October 1988 to October 1991, 170 patients were randomized to receive either IFN-alpha or busulfan. Of 159 eligible patients, 31 (38.8%) of 80 patients in the IFN-alpha group and 43 (54.4%) of 79 patients in the busulfan group achieved complete hematologic remission, and 38.8% in the IFN-alpha group and 43.0% in the busulfan group achieved partial hematologic remission. A complete cytogenetic response was induced in seven (8.8%) of 80 patients treated with IFN-alpha and two (2.5%) of 79 patients treated with busulfan, and a partial cytogenetic response was 7.5% (6/80) and 2.5% (2/79), respectively. The difference in major (complete and partial) cytogenetic response between the two groups was significant (P = .046). At a median follow-up of 50 months, the predicted 5-year survival rate was 54% in the IFN-alpha group and 32% in the busulfan group (P = .0290), and the predicted 5-year rate of remaining in chronic phase was 41% in the IFN-alpha group and 29% in the busulfan group (P = .1165). As compared with the patients with no cytogenetic response, the patients with any cytogenetic response (complete, partial or minor) after the IFN-alpha or busulfan treatment were significantly superior in the duration of chronic phase (IFN-alpha group; P = .0017, busulfan group; P = .0010) even after correction for the time to response using the landmark analysis. However, there was no significant difference in survival rate in the IFN-alpha group (P = .1065). There was no significant difference in survival rate (P = .3923) and the duration of chronic phase (P = .6258) between the IFN- alpha and the busulfan group in the patients with a cytogenetic response (complete, partial or minor). These results demonstrate that IFN-alpha treatment produces a significantly superior cytogenetic response and survival rate as compared with the busulfan treatment, and unexpectedly, that busulfan can also eliminate Philadelphia chromosome positive clone in a few patients who showed prolonged survival rate and duration of chronic phase.     

Homoharringtonine in newly diagnosed acute promyelocytic leukemia treatment: a prospective,randomized controlled trial

<正>Objective To compare the efficacy and toxicities of combining homoharringtonine(HHT)±daunorubicin(DNR)with all-transretinoic acid(ATRA)based therapy and DNR plus ATRA based therapy in newly diagnosed low/intermediate risk acute promyelocytic leukemia(APL).Methods A total of 96 newly diagnosed pa-     

High-dose cytosine arabinoside and daunorubicin postremission therapy in adults with de novo acute myeloid leukemia

A total of 149 consecutive de novo AML patients aged 50 years or less (median age = 37 years) were enrolled in this prospective multicenter trial initiated in May 1985. All patients received the same induction and early consolidation therapy with daunorubicin (DNR), cytosine arabinoside (Ara-C), and etoposide (DAV). High-dose Ara-C/DNR therapy included Ara-C at 3 g/m², in 12 doses (HD-Ara-C/DNR I) and eight doses (HD-Ara-C/DNR II), followed by DNR 30 mg/m² for 3 days. A complete remission (CR) was achieved in 104 (70%) patients; 61 complete responders received at least one cycle with HD-Ara-C/DNR. If those patients who were transplanted in first CR (n=26), were not considered, the median relapsefree-survival (MRFS) of the remaining 78 patients was 15 months, with a probability of relapse-free survival (RFS) at 116 months of 30% (95% CI, 20–40%) after a median follow-up of 95 months. The MRFS of the HD-Ara-C/DNR consolidated patients was 25 months, with a probability of RFS at 116 months of 37% (95% CI, 24–50%). If all patients who were transplanted (n=44) were not considered, the median survival time (MST) was 18 months with a probability of being alive at 118 months of 24% (95% CI, 16–33%). MST of the HD-Ara-C/DNR consolidated patients was 58 months with a survival probability of 46% (95% CI, 31–60%) at 118 months. Prognostic factor analysis did not reveal any significant influence of age, sex, FAB subtype, white blood cell count, hemoglobin level, thrombocyte count, LDH, or response to the first induction course on RFS of the HD-Ara-C/DNR consolidated patients. In summary, HD-Ara-C/DNR consolidation can improve the long-term outcome of a subgroup of de novo AML patients. Further improvement of the outcome seems to depend on the identification of patients with an inferior outcome under that strategy who might benefit from alternative treatment strategies.     

Treatment options for newly diagnosed patients with adult acute lymphoblastic leukemia

The treatment of adults with acute lymphoblastic leukemia (ALL) has been modeled on therapy developed for childhood ALL. The similarity between childhood and adult forms of this disease allows for inferences to be drawn from experience in the pediatric population. However, adults with ALL have far poorer outcome when compared to children. Some of this difference can be attributed in ability to tolerate intensive therapy coupled with an increased incidence of unfavorable cytogenetic subgroups and a decreased incidence of favorable cytogenetic subgroups. Treatment of adult ALL is typically divided into four broad categories: induction, consolidation, maintenance, and central nervous system prophylaxis. Despite three decades of clinical investigation for devising improved treatment programs for adults with ALL, no single program has emerged as the standard. Here we review classification, prognostic features, current treatment programs, and new advances as applied to adult patients with newly diagnosed ALL.     

A randomized trial comparing standard versus high-dose daunorubicin induction in patients with acute myeloid leukemia

We conducted a phase 3 randomized trial comparing 2 different doses of daunorubicin as induction chemotherapy in young adults (60 years of age or younger) with acute myeloid leukemia (AML). Of 383 patients who were analyzed, 189 received standard-dose daunorubicin (SD-DN, 45 mg/m2 per day times 3 days) and 194 received high-dose daunorubicin (HD-DN, 90 mg/m2 per day times 3 days) in addition to cytarabine (200 mg/m2 per day times 7 days) to induce complete remission (CR). The CR rates were 72.0% in the SD-DN arm and 82.5% in the HD-DN arm (P = .014). At a median follow-up of 52.6 months, overall (OS) and event-free (EFS) survival were higher in the HD-DN arm than in the SD-DN arm (OS, 46.8% vs 34.6%, P = .030; EFS, 40.8% vs 28.4%, P = .030). Differences in CR rate and both OS and EFS remained significant after adjusting for other variables (CR, hazard ratio [HR], 1.802, P = .024; OS, HR, 0.739, P = .032; EFS, HR, 0.774, P = .048). The survival benefits of HD-DN therapy were evident principally in patients with intermediate-risk cytogenetic features. The toxicity profiles were similar in the 2 arms. In conclusion, HD-DN improved both the CR rate and survival duration compared with SD-DN in young adults with AML. This study is registered at www.clinicaltrials.gov as #NCT00474006.     

High-dose cytosine arabinoside and mitoxantrone in previously-treated acute leukemia patients

35 patients with refractory or relapsed acute leukemia received salvage chemotherapy using high-dose cytosine arabinoside 2 g/m2 intravenously for 3 hours every 12 h, in 8 doses, followed by continuous infusion of mitoxantrone 12 mg/m2/day for 2 d. 9 patients had acute myeloblastic leukemia (AML), (4 relapsed, 5 refractory), 20 had acute lymphoblastic leukemia (ALL) (11 relapsed, 9 refractory) and 6 had chronic myelogenous leukemia (CML) in the blastic phase (BP). 4 out of 9 AML and 16 out of 20 ALL achieved complete remission. Median survival was 6 months for all patients and 10 months for responders. A short (1.5 months) chronic phase was achieved in 3 patients with CML. The main toxic effect was hematologic. A pharmacokinetic study was performed on mitoxantrone. No correlation was found with clinical response. The combination of mitoxantrone and ara-C is an effective antileukemic regimen, especially in ALL.     

A randomized comparison of postremission therapy in acute myelogenous leukemia: a Southeastern Cancer Study Group trial

The Southeastern Cancer Study Group conducted a post-remission induction randomized trial in adult acute myelogenous leukemia to assess the efficacy of alternate drug therapy during consolidation and of immunotherapy during maintenance. Of 508 evaluable patients entered into the study, 335 (66%) achieved a complete remission treated with a 7-day infusion of cytosine arabinoside at a dose of 100 mg/sq m/day and 3 days of daunorubicin at a dose of 45 mg/sq m/day. Those in remission were randomized to receive 3 courses of 1 of 3 consolidation regimens: (A) a continuous infusion of 5-azacytidine, 150 mg/sq m/day for 5 days; (B) 5-azacytidine plus beta-deoxythioguanosine, 300 mg/sq m/day for 5 days; or (C) cytosine arabinoside, 100 mg/sq m/day intravenously, and thioguanine, 100 mg/sq m orally every 12 hr, plus daunorubicin, 10 mg/sq m every 24 hr daily for 5 days. There was no difference in relapse rate among the 3 arms. Those completing consolidation and remaining in remission were randomized to 1 of 3 maintenance regimens: (D) chemotherapy, 5-day infusion of cytosine arabinoside and 2 days of daunorubicin (same doses as induction) given every 13 wk for 1 yr; (E) BCG given twice weekly for 1 mo and then monthly for 1 yr; or (F) the combination of regimens D and E. The median duration of remission was significantly better on regimen D (17.4 versus 9.4 and 9.5 mo), and median survival was 29 mo compared to 21 mo for the other regimens. Those given different drugs during consolidation than used for induction (regimens A and B) and subsequent chemotherapy for maintenance (regimen D) had the longest remission durations and survival. Immunotherapy was not as good as intensive chemotherapy for maintenance.     

Treatment of adult acute lymphoblastic leukemia with cytosine arabinoside, vincristine, and prednisone.

Thirteen adults with acute lymphoblastic leukemia were entered into a protocol in which cytosine arabinoside infusion was added to vincristine and prednisone as remission induction and periodic intensification therapy. Central nervous system prophylaxis consisting of cranial irradiation and intrathecal methotrexate was given, and all patients received continuous oral 6-mercaptopurine and methotrexate as maintenance treatment. Myelotoxicity was severe during induction, with prolonged granulocyte and platelet count nadirs noted. Nine of 13 patients (69%) obtained a complete remission and one (8%) obtained a partial remission. The median duration of complete remission was 38.1 weeks. It was concluded that cytosine arabinoside in combination with vincristine and prednisone is an effective but toxic antileukemic regimen which did not produce a major improvement in remission duration.     

Efficacy of daunorubicin in the therapy of adult acute lymphocytic leukemia: a prospective randomized trial by cancer and leukemia group B

The efficacy of the addition of intensive therapy with daunorubicin (45 mg/m2 IV on days 1, 2, 3) to an otherwise identical induction program consisting of vincristine, prednisone, and L-asparaginase was assessed in 177 previously untreated adults (greater than or equal to 20 years of age) with acute lymphocytic leukemia (ALL). In the prospectively randomized phase of the investigation, 46 patients received daunorubicin in induction, whereas 53 did not. The two groups were otherwise comparable for pretreatment variables. A complete response was observed in 38/46 patients (83%) treated with daunorubicin, compared to 25/53 (47%) induced with vincristine, prednisone, and L- asparaginase alone (P = .003). The high response rate attributable to the use of the anthracycline was confirmed by the nonrandomized treatment of 78 subsequent patients, in whom a complete response rate of 76% was attained. A common program for central nervous system therapy and for maintenance therapy was employed in 103 patients achieving complete response. Maintenance consisted of cycles of 6- mercaptopurine (6-MP) and methotrexate with periodic reinforcement with vincristine and prednisone. Maintenance therapy proved to be minimally toxic. The average duration of complete response was 15 months and was not affected by the induction program employed. Approximately 25% of responders are projected to remain in continuing complete response for 36 months. The failure of the daunorubicin-containing programs to produce a higher percentage of long-term survivors, despite the higher complete response rates achieved, was thought to be due to the use of a maintenance program that was weak in intensity and dependent on reinforcement with vincristine and prednisone. These data clearly establish the increased effectiveness of vincristine, prednisone, L- asparaginase, and daunorubicin, as compared to this combination without daunorubicin, in the induction of complete response in adults with ALL. The results support the concept of an intensive, rather than a conservative, chemotherapeutic approach as the most appropriate strategy for the treatment of adult ALL.     

Randomized phase II study of two schedules of flavopiridol given as timed sequential therapy with cytosine arabinoside and mitoxantrone for adults with newly diagnosed, poor-risk acute myelogenous leukemia

Background

Flavopiridol is a protein-bound, cytotoxic, cyclin dependent kinase inhibitor. A phase II trial of flavopiridol followed by ara-C and mitoxantrone with flavopiridol given by 1-h bolus for adults with newly-diagnosed, poor-risk acute myelogenous leukemia yielded 67% complete remission with median disease-free survival of 13.6 months.

Design and Methods

We compared bolus flavopiridol (50 mg/m²/day, Arm A) versus ''hybrid'' flavopiridol (30 mg/m² over 30 min followed by 40 mg/m² over 4 h, Arm B) followed by ara-C and mitoxantrone in 78 patients (39 per arm) with newly diagnosed, poor-risk acute myelogenous leukemia. To mitigate imbalance, patients were stratified by presence or absence of secondary leukemia and therapy for antecedent disorder.

Results

Death at or before Day 60 occurred in 8% of patients per arm. Complete remission plus complete remission with incomplete recovery was 68% (Arm A, 62%; Arm B, 74%) overall, and 65% or over in both arms for patients with secondary leukemia and leukemia with adverse genetics. In Arm A 91% and in Arm B 86% of patients received chemotherapy and/or allogeneic transplantation in complete remission. Median overall survival for all remission patients has not been reached for either arm, with median disease free survival of 13.6 months for Arm A and of 12.0 months for Arm B.

Conclusions

Both flavopiridol schedules produce comparably encouraging results in adults with poor-risk acute myelogenous leukemia. Given the greater ease of bolus administration, we are conducting a randomized phase II study of bolus flavopiridol followed by ara-c and mitoxantrone versus conventional induction therapy for patients aged 70 years and under with intermediate or poor-risk acute myelogenous leukemia. This study is registered at www.clinicaltrials.gov as #{"type":"clinical-trial","attrs":{"text":"NCT 00407966","term_id":"NCT00407966"}}NCT 00407966.Key words: acute myelogenous leukemia, poor risk, flavopiridol, ara-C, mitoxantrone     

A randomized trial of conventional dose vs reduced dose in BHAC-DM therapy for acute myelogenous leukemia in elderly patients

Twenty-nine patients aged 60-75 years with newly diagnosed acute myelogenous leukemia (AML) were randomized to receive BHAC-DM either at a reduced dose (S-1 group, n = 13; BHAC 150 mg/m2 1-7 day, DNR 30 mg/m2 1-3 day, 6MP 70 mg/m2 1-7 day) or the conventional dose (S-2 group, n = 16; BHAC 200 mg/m2 1-7 day, DNR 40 mg/m2 1-3 day, 6MP 70 mg/m2 1-7 day). On day 7, patients were given therapy for 2 more days if the ratio of blasts in their bone marrow was more than 15%. Granulocyte-colony stimulating factor was injected when the leukocyte count decreased below 1,000/microliter. The rates of complete remission were 46.2% in the S-1 group and 43.8% in the S-2 group. No significant differences in response distinguished the 2 groups. The mortality rate during myelosuppression was 1/13 in the S-1 group and 1/16 in the S-2 group. The rate of treatment-related death was 10.1% for all patients. Grade-4 adverse effects were not seen in any of the patients. We concluded that the conventional dose of BHAC-DM was as acceptable as the reduced dose in elderly patients with AML.     

Cell kinetics after high dose cytosine arabinoside in patients with acute myelocytic leukemia

Summary In this study 10 patients with acute myelocytic leukemia (AML) each received a rapid intravenous injection of high dose cytosine arabinoside (HD Ara-C; 1 g/m²). Bone marrow aspirates were obtained before and after Ara-C administration to determine the percentage of cells in S-phase measured by flow cytometry. In 5 out of 10 cases synchronization of the leukemic cells in S-phase of the cell cycle was observed. However, the time of maximum synchronization turned out to be difficult to predict. Therefore, the strong correlation between percentage of cells in S-phase at diagnosis and the time of maximal accumulation of S-phase cells after Ara-C administration, as observed by others in childhood AML, could not be confirmed for adult AML patients. Although synchronization of AML cells after in vivo Ara-C administration could be demonstrated in at least half of the patients, the practical consequences are such that clinical application was hampered.