Prognostic factors and follow-up parameters in patients with paroxysmal nocturnal hemoglobinuria (PNH): experience of the Austrian PNH network.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease characterized by a deregulated complement system, chronic Coombs-negative, intravascular hemolysis, and a variable clinical course with substantial risk to develop thromboembolic events. We analyzed diagnostic and prognostic parameters as well as clinical endpoints in 59 adult patients suffering from PNH in 5 hematology centers in Austria (observation period: 1978-2015). Median follow-up time was 5.6 years. The median clone size at diagnosis amounted to 55% and was higher in patients with classical PNH (81%) compared to patients with PNH associated with aplastic anemia (AA) or myelodysplastic syndromes (MDS) (50%). The clone size also correlated with lactate dehydrogenase (LDH) levels. In one patient, anemia improved spontaneously and disappeared with complete normalization of LDH after 16 years. Seventeen patients received therapy with eculizumab. The rate of thromboembolic events was higher in the pre-eculizumab era compared with eculizumab-treated patients but did not correlate with the presence of age-related clonal hematopoiesis or any other clinical or laboratory parameters. Peripheral blood colony-forming progenitor cell counts were lower in PNH patients compared with healthy controls. Only two patients with classical PNH developed MDS. Overall, 7/59 patients died after 0.5-32 years. Causes of death were acute pulmonary hypertension, Budd-Chiari syndrome, and septicemia. Overall survival (OS) was mainly influenced by age and was similar to OS measured in an age-matched healthy Austrian control cohort. Together, compared with previous times, the clinical course and OS in PNH are favorable, which may be due to better diagnosis, early recognition, and eculizumab therapy.

High platelet count associated with venous thromboembolism in cancer patients: results from the Vienna Cancer and Thrombosis Study (CATS).

BACKGROUND: In cancer patients, laboratory parameters that predict venous thromboembolism (VTE) are scarce. Increased platelet count has been found to be a risk factor for VTE in cancer patients receiving chemotherapy (CHT). We have assessed high platelet count as a risk predictor for VTE in patients with cancer undergoing discriminative anti-cancer treatments and investigated whether platelet count correlates with thrombopoietin (TPO) levels. DESIGN AND METHODS: The Cancer and Thrombosis Study (CATS) is an ongoing prospective observational study of patients with newly diagnosed cancer or progression of disease, which started in October 2003. Occurrence of VTE and information on the patients' anti-cancer treatment during follow-up were recorded. RESULTS: Between October 2003 and February 2008, 665 patients with solid tumors were included (314 female/351 male, mean age 62 years). VTE occurred in 44 patients (18 female/26 male, mean age 62 years). The cumulative probability of VTE after 1 year was 34.3% in patients with a platelet count (PC) above the 95th percentile representing 443 x 10(9)/L compared with 5.9% in those below 443 x 10(9)/L. High platelet count [hazard ratio (HR): 3.50, 95% confidence interval (CI): 1.52-8.06, P = 0.0032], soluble P-selectin [HR: 2.66, 95% CI: 1.42-4.96, P = 0.0021] and surgery [HR: 4.05, 95% CI: 1.74-9.46, P = 0.0012] were statistically significant risk factors for VTE in multivariable analysis along with leucocyte count, age, gender, radio- and CHT. We found no correlation between platelet count and TPO levels. CONCLUSIONS: High PC is a clinically important, independent risk predictor for VTE in cancer patients. PC was not found to be associated with TPO levels.

Gene expression signature of chronic lymphocytic leukaemia with Trisomy 12.

BACKGROUND: The prognosis of chronic lymphocytic leukaemia (CLL) patients is largely determined by the karyotype of the malignant clone. We have investigated the gene expression profile associated with trisomy 12 (+12). DESIGN: Initially, unselected peripheral blood mononuclear cells of four patients with +12 were compared with 16 CLL controls using microarray analysis. RESULTS: were validated by quantitative real-time PCR with RNA from 61 patients (29 with +12, 32 CLL controls). Results Seven genes showing the strongest correlation with +12 in microarray analysis were selected for real-time PCR: HIP1R, MYF6, SLC2A6, CD9 (overexpressed); CD200, P2RY14, RASGRP3 (underexpressed). Four genes were significantly associated with +12: HIP1R (P<0.0001), MYF6 (P=0.007), P2RY14 (P=0.014), CD200 (P=0.028). Receiver Operating Characteristic curve analysis revealed that HIP1R expression was a highly sensitive and specific marker for +12 in CLL patients. MYF6 was exclusively expressed in normal or malignant B cells in peripheral blood but was poorly predictive for +12. As expected, a number of overexpressed genes are located on chromosome 12 (HIP1R, MYF6). Interestingly, both significantly underexpressed genes (P2RY14, CD200) reside on the long arm of chromosome 3 pointing to trans-repression in this region. CONCLUSIONS: Analysis of the molecular signature of trisomy 12 in CLL resulted in: (i) identification of a surrogate marker for PCR (HIP1R); (ii) observation of a gene dosage effect; and (iii) detection of specific underexpression of genes located on chromosome 3. These results should help to improve diagnosis and treatment decisions for patients with CLL and trisomy 12.

Dasatinib inhibits progenitor cell proliferation from polycythaemia vera.

BACKGROUND: A mutation of Janus kinase 2 V617F is present in most patients with polycythaemia vera (PV). However, it is generally believed that JAK2(V617F) is not the sole molecular abnormality in PV. Since dasatinib is currently evaluated in patients with PV, it is of interest to study the effects of dasatinib on the growth of clonal progenitor cells in vitro. DESIGN AND METHODS: Peripheral blood mononuclear cells from patients with PV, chronic myeloid leukaemia (CML) and controls were exposed to dasatinib (0.1 to 500 nm mL(-1)). Colony growth was stimulated by interleukin-3, granulocyte-macrophage colony-stimulating factor and erythropoietin. Endogenous erythroid colony (EEC) growth was investigated without exogenous cytokines. Real-time PCR was performed to assess the percentage of JAK2(V617F) cells. RESULTS: 10 nm of dasatinib suppressed EEC growth from PV by 89% (P = 0.002). This inhibition was dose dependent and occurred at pharmacological concentrations. Erythroid and myeloid colony growth was also significantly suppressed in the presence of exogenous cytokines. When compared to PV the inhibition of stimulated colony growth was significantly less pronounced in controls but tended to be more vigorous in CML. Interestingly, despite the potent inhibition of PV cells real-time PCR revealed that the numbers of JAK2(V617F) transcripts did not decrease upon exposure to dasatinib. CONCLUSION: This study shows a marked inhibition of the proliferative capacity of progenitor cells from PV. Although JAK2(V617F) transcript levels did not decrease upon exposure to dasatinib, the drug might suppress PV progenitors through inhibition of a yet undefined molecular target.

Systemic lupus erythematosus patients exhibit functional deficiencies of endothelial progenitor cells.

OBJECTIVE: SLE is characterized by an increased cardiovascular risk. Since endothelial progenitor cells (EPCs) have been described to serve as a biomarker for the CV risk and are known to be depleted in various diseases, we were interested if SLE would also be associated with altered peripheral EPC levels or functional abnormalities of these cells. METHODS: EPCs were quantified in 31 female SLE patients with different disease activity and in age-matched healthy controls (HCs) by FACS analysis and by colony forming unit (CFU) assay. Furthermore, EPC adhesion and migration capacity were tested. RESULTS: EPC levels were similar in HC and SLE when assessed by FACS (0.045 +/- 0.006% vs 0.036 +/- 0.007% within the lymphocyte gate) and by the CFU assay (18 +/- 3 vs 15 +/- 2 colonies/well). No correlation with disease activity could be observed, but SLE patients treated with chloroquine exhibited significantly decreased EPC levels (0.058 +/- 0.005% without vs 0.024 +/- 0.008% with chloroquine, P < 0.05). Addition of chloroquine to in vitro cultures also led to a decreased colony formation in SLE and in HC. When testing the adhesion and migration capacity of EPC on human umbilical vein endothelial cells (HUVEC), cells from SLE patients had reduced adhesion (19.2 +/- 3.5% vs 36.6 +/- 5.2% EPC/high power field, P < 0.02) and migratory activity (56 +/- 6 cells/random microscopic field in SLE vs 121 +/- 28 in controls, P < 0.02). CONCLUSION: The data reveal that EPCs are significantly affected in SLE. While circulating EPC levels are in the range of HC, they exhibit functional deficiencies that may lead to impaired tissue availability.

Prognostic significance of serial determinations of lactate dehydrogenase (LDH) in the follow-up of patients with myelodysplastic syndromes.

BACKGROUND: Early recognition of disease progression in low-risk myelodysplastic syndromes (MDS) is an important decision point concerning intensive therapies. In a screen program searching for dynamic prognostic determinants, we have identified lactate dehydrogenase (LDH) as a most suitable follow-up parameter. PATIENTS AND METHODS: LDH levels were serially determined in 221 patients with de novo MDS (median age 70 years, range 24-94). The increase in LDH was correlated with survival and acute myeloid leukemia (AML) evolution. RESULTS: Confirming previous data, an elevated LDH at diagnosis was found to be associated with an increased probability of AML evolution and decreased probability of survival (P < 0.05). In the follow-up, we found that in patients who progressed (to higher IPSS category or AML), LDH levels were significantly higher in the two 3-month period preceding progression compared with the initial two 3-month period (P < 0.005). In a subgroup of patients, the increase in LDH was accompanied or followed by other signs of disease progression, such as occurrence of thrombocytopenia or appearance of circulating blasts. In multivariate analyses, the LDH increase was found to be an independent prognostic variable. CONCLUSIONS: LDH is an interesting follow-up parameter in MDS, which may assist in early recognition of disease progression and thus help in risk stratification and patient selection for interventional therapies.

Liposomal cytarabine for treatment of myeloid central nervous system relapse in chronic myeloid leukaemia occurring during imatinib therapy.

BACKGROUND: Central nervous system (CNS) relapse in chronic myeloid leukaemia (CML) is rare and if recorded is usually found to occur in patients with lymphoblastic transformation. The BCR/ABL tyrosine kinase inhibitor imatinib is highly effective in patients with CML, but hardly crosses the blood-brain barrier. PATIENTS AND METHODS: We report on two CML patients who developed a myeloid CNS relapse during treatment with imatinib. One patient was in major cytogenetic response at the time of CNS relapse. In both cases, the myeloid origin of neoplastic cells in the cerebrospinal fluid (CSF) was demonstrable by immunophenotyping, and their leukaemic origin by detection of the BCR/ABL oncoprotein. No BCR/ABL kinase domain mutations were found. Both patients received intrathecal liposomal cytarabine (50 mg each cycle; 6 cycles). In one patient, additional CNS radiation was performed, whereas in the other, consecutive treatment with dasatinib (70 mg per os twice daily) was started. RESULTS: In response to therapy, the clinical symptoms resolved, and the leukaemic cells in the CSF disappeared in both cases. After three months of observation, both patients are in complete cytogenetic and major molecular response, without evidence for a systemic or a CNS relapse. CONCLUSIONS: 'Anatomic' resistance against imatinib in the CNS can lead to a myeloid CNS relapse. Liposomal cytarabine with or without radiation is effective as local therapy in these patients. For systemic treatment and prophylaxis, BCR/ABL kinase inhibitors crossing the blood-brain barrier such as dasatinib should be considered in patients with CNS relapse.

In vivo effects of imatinib mesylate on human haematopoietic progenitor cells.

BACKGROUND: Imatinib mesylate has considerable antineoplastic activity in patients with chronic myeloid leukaemia (CML) and some solid tumours. Although originally regarded as nontoxic for normal haematopoiesis, mild to moderate myelosuppression is a commonly observed side-effect of this treatment. Recently, this molecule has been shown to suppress normal haematopoietic progenitor cells in vitro. This is the first study that has investigated the effect of imatinib on haematopoietic progenitor cells in vivo. MATERIALS AND METHODS: We investigated the number of circulating haematopoietic progenitor cells in 79 patients with CML and five patients with solid tumours who were treated with imatinib for at least 3 months. Bone marrow progenitor cells were assessed in a subgroup of 18 patients with CML after 12 months of imatinib treatment. Results were compared with haematopoietic progenitor cell numbers of normal controls. RESULTS: Circulating progenitors of all classes were significantly decreased in CML up to 24 months of imatinib therapy compared with healthy controls (median progenitor cells in CML after 12 months: CFU-GM 62, range 0-2543; BFU-E 216, range 0-3259; CFU-GEMM 0, range 0-139; versus controls: CFU-GM 208, range 50-936; BFU-E 690, range 120-1862; CFU-GEMM 20, range 4-77; P < 0.001). Similar reductions in the number of progenitor cells derived from bone marrow were found in a subgroup of 18 patients with CML. In patients with solid tumours the number of circulating progenitor cells was significantly lower under treatment with imatinib when compared with the controls. Withdrawal of imatinib in a patient with a malignant brain tumour resulted in a prompt normalization of circulating progenitors. CONCLUSIONS: This study suggests that imatinib exerts myelosuppressive effects through inhibition of haematopoietic progenitor cells.

High expression of lipoprotein lipase in poor risk B-cell chronic lymphocytic leukemia.

We investigated the pattern of lipoprotein lipase (LPL) expression in B-cell chronic lymphocytic leukemia (B-CLL) and assessed its prognostic relevance. Expression of LPL mRNA as well as protein was highly restricted to leukemic B cells. The intensity of intracellular immunoreactivity of LPL was higher in samples of patients with unmutated immunoglobulin heavy-chain variable region genes (IGV(H)) compared to those with mutated IGV(H) genes. LPL mRNA levels in peripheral blood mononuclear cells (PBMNC) from 104 CLL patients differed by 1.5 orders of magnitude between cases with mutated (N=51) or unmutated (N=53) IGV(H) (median: 1.33 vs 45.22 compared to normal PBMNC). LPL expression correlated strongly with IGV(H) mutational status (R=0.614; P<0.0001). High LPL expression predicted unmutated IGV(H) status with an odds ratio of 25.90 (P<0.0001) and discriminated between mutated and unmutated cases in 87 of 104 patients (84%). LPL expression was higher in patients with poor risk cytogenetics. High LPL expression was associated with a shorter treatment-free survival (median 40 vs 96 months, P=0.001) and a trend for a shorter median overall survival (105 months vs not reached). Our data establish LPL as a prognostic marker and suggest functional consequences of LPL overexpression in patients with B-CLL.

High expression of activation-induced cytidine deaminase (AID) mRNA is associated with unmutated IGVH gene status and unfavourable cytogenetic aberrations in patients with chronic lymphocytic leukaemia.

Activation-induced cytidine deaminase (AID) is essential for somatic hypermutation of B-cells. We investigated the expression of AID mRNA by real-time polymerase chain reaction (PCR) in peripheral blood mononuclear cells of 80 patients with B-CLL. AID expression was detected in 45 of 80 patients (56%) at various levels, but was undetectable in 35 patients (44%). AID PCR positivity was associated with unmutated IGV(H) gene status (22 of 25 patients; P=0.002) and unfavourable cytogenetics (18 of 23 patients with deletion in 11q or loss of p53; P=0.040). Using a threshold level of 0.01-fold expression compared to Ramos control cells, even more significant associations were observed (P=0.001 for IGVH; P=0.002 for cytogenetics). A correlation was observed between individual AID levels and the percentage of V(H) homology (R=0.41; P=0.001). AID positivity predicted unmutated IGV(H) status with an odds ratio of 8.31 (P=0.003) and poor risk cytogenetics with an odds ratio of 3.46 (P=0.032). Significance was retained after adjustment for Binet or Rai stages. AID mRNA levels were stable over time. These data suggest a potential role of AID as a prognostic marker in B-CLL.

Impact of cytogenetics on the prognosis of adults with de novo AML in first relapse.

Karyotype is an important prognostic factor in patients with newly diagnosed acute myeloblastic leukaemia (AML). The prognostic value of cytogenetics on the outcome of patients with AML in relapse has not yet been well defined. We analysed the clinical outcome of 152 patients with de novo, chemotherapy-treated AML in first relapse according to the cytogenetic classification of the United Kingdom Medical Research Council. The rate of second complete remission (CR) (88, 64 and 36%) and the probability of survival at 3 years (43, 18 and 0%) were significantly different between the favourable, intermediate and adverse cytogenetic risk groups, respectively. Compared to the favourable group, the relative risk (RR) of death (multivariate analyses) was 2.6 (confidence interval (CI): 1.5-4.4, P<0.001) for the intermediate and 3.7 (CI: 1.7-7.9, P=0.001) for the adverse group. The prognostic value of the duration of first CR was confirmed (RR of death: 2.0 (CI: 1.0-4.0) for each additional year in first CR), whereas the FLT3 mutation obtained at diagnosis did not markedly influence the outcome of patients with AML in relapse. In conclusion, our results indicate that both karyotype and the duration of first CR are independent prognostic factors for patients with de novo AML in first relapse.

Numbers of colony-forming progenitors in patients with systemic mastocytosis: potential diagnostic implications and comparison with myeloproliferative disorders.

BACKGROUND: An increase in colony-forming progenitor cells (CFU) is typically seen in myeloproliferative disorders (MPD). Systemic mastocytosis (SM) is a haemopoietic neoplasm involving myeloid progenitors similar to MPD. In the present study, we measured the levels of peripheral blood (pb) and bone marrow (bm) CFU in patients with different categories of SM, and compared them with those obtained in MPD patients and healthy controls. MATERIALS AND METHODS: Numbers of CFU (CFU-GM, BFU-E, CFU-GEMM) were measured in a colony assay in 25 patients with SM [indolent SM (ISM), n = 15; smouldering SM (SSM), n = 3; SM with an associated haematologic clonal non-mast cell lineage disease (SM-AHNMD), n = 5; aggressive SM (ASM), n = 1; mast cell leukaemia (MCL), n = 1] and 37 with MPD [chronic myeloid leukaemia (CML), n = 10; polycythemia vera (PV), n = 8; essential thrombocytosis (ET), n = 9; idiopathic myelofibrosis (IMF), n = 10]. RESULTS: In the patients with MPD, elevated numbers of pb CFU were detected in all groups when compared with healthy controls (P < 0.05). In most of the patients with ISM, circulating CFU levels (CFU-GM, BFU-E, and CFU-GEMM) were within the normal range. In SSM, pb CFU-GM levels were normal in two patients, and elevated in a third patient. In the "SM-AHNMD-group", CFU levels were found to reflect the nature of the AHNMD: in SM with concomitant acute myeloid leukaemia (SM-AML, n = 2), the levels of CFU were low or undetectable, whereas in SM with chronic myelomonocytic leukaemia (SM-CMML, n = 2), elevated numbers of pb CFU-GM were found. CONCLUSION: The numbers of CFU are normal in patients with ISM, but elevated in some patients with SSM and SM-CMML. An elevated CFU level in SM should raise the suspicion of an associated MPD (CMML) or smouldering SM, a novel SM-subtype that shares several features with MPD and sometimes progresses to an overt SM-MPD.

Circulating myeloid colony-forming cells predict survival in myelodysplastic syndromes.

The growth characteristics and the prognostic value of cytokine-stimulated myeloid colony formation from peripheral blood mononuclear cells (PBMC) of patients with myelodysplastic syndromes (MDS) are largely unknown. In this study we have determined the number of myeloid colony-forming units (mCFUs) in semisolid medium from 112 MDS patients and correlated them with French-American-British (FAB) type, the international prognostic scoring system (IPSS), karyotype, peripheral blood (PB) and bone marrow (BM) blast cells, cytopenias, lactate dehydrogenase (LDH), and survival data. Concerning the FAB classification, lower median mCFUs were found in patients with refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) compared to refractory anemia with excess of blast cells (RAEB) and refractory anemia with excess of blasts cells in transformation (RAEB-T). In vitro growth in MDS clearly correlated with the cytogenetic risk groups defined by the IPSS (30.5/10(5) PBMCs with favorable karyotypes, 191 in the intermediate prognostic group, 677 with unfavorable cytogenetics, p=0.015 favorable vs unfavorable). BM blast cells >5% (60.5 vs 255 colonies, p=0.032) as well as LDH levels above the normal limit (64.5 vs 425 colonies, p=0.045) were also associated with higher colony formation. Patients were stratified according to the number of circulating mCFUs into a low growth, intermediate growth and high growth group. Median survival was 343 days in the high growth, 1119 days in the low growth, and 2341 days in the intermediate growth group ( p=0.0002). Multivariate analyses revealed colony growth ( p=0.0056), PB blast cells ( p=0.0069), cytogenetic risk group ( p=0.024), and platelet count ( p=0.018) to predict survival in our patients. After inclusion of the IPSS risk categories, mCFU levels remained a highly predictive parameter for survival ( p=0.0056) and acute myeloblastic leukemia (AML) transformation ( p=0.0003).

A comparative study on demographic, hematological, and cytogenetic findings and prognosis in acute myeloid leukemia with and without leukemia cutis.

We studied the incidence of leukemia cutis (LC) in 381 consecutive patients with acute myeloid leukemia (AML) in a single institution and compared the demographic, hematological, and cytogenetic findings in AML patients with and without LC. We also examined the response to intensive chemotherapy, overall survival, and duration of remission in this patient population with regard to the presence of LC. The prevalence of LC was 3.7% in clinically diagnosed patients and 2.9% in biopsy-proven cases, respectively. Patients with and without LC did not differ with regard to age, sex, white blood cell counts, hemoglobin, fibrinogen, and platelet counts at diagnosis, but lactate dehydrogenase (LDH) was significantly higher in patients with LC. Various karyotype abnormalities were found, but in patients with LC numerical abnormalities of chromosome 8 were significantly more common ( P<0.0001). Patients with LC did not differ from patients without LC with regard to remission rate, but there was a trend towards shorter remission duration in patients with LC. We conclude that patients with LC have some features different from patients without this symptom. The increased frequency of numerical aberrations of chromosome 8 in patients with LC was the most interesting observation of our study. The pathophysiological significance of this finding remains to be determined.

Kinetics of CFU-Mk after automated plateletpheresis.

BACKGROUND AND OBJECTIVES: Platelet count, thrombopoetin (TPO) level and the compartment of megakaryocyte progenitor cells (CFU-Mk) are major determinants in the regulation of thrombopoiesis. The aim of this study was to investigate the potential changes in the compartment of CFU-Mk and their correlation with serum TPO levels and platelet count after plateletpheresis. MATERIALS AND METHODS: Twelve healthy individuals were randomly assigned to undergo single-donor plateletpheresis. A collagen-based in vitro culture system was used to determine the number of peripheral blood (PB) CFU-Mk before and after donation and on days 1, 4 and 7 thereafter. TPO levels were measured by a specific enzyme-linked immunosorbent assay and whole blood counts were performed using an automated cell counter. RESULTS: The pre-apheresis platelet count (mean +/- SEM: 276 +/- 13 x 10(9)/l) decreased after plateletpheresis to a nadir of 194 +/- 8 x 10(9)/l (P < 0.001), showed a gradual increase on days 1 and 4, and reached pre-apheresis values by day 7 (280 +/- 11). The serum TPO levels were found to be significantly increased on days 1 and 7 as compared to baseline levels (baseline value 103.3 +/- 18.5 pg/ml versus day-1 value 135.8 +/- 25.8 pg/ml and day-7 value 132 +/- 30.19 pg/ml; P < 0.03 and P < 0.03, respectively). The numbers of CFU-Mk in PB were significantly elevated on day 4 only (125 +/- 21 colonies/ml of PB versus pre-apheresis values of 68 +/- 18 colonies/ml of PB, P < 0.005). CONCLUSIONS: These findings suggest that platelet loss during plateletpheresis affects thrombopoiesis at the progenitor cell level, probably through alterations in TPO plasma concentrations.

Suspect cell convolutes in the bone marrow of a patient with renal cell carcinoma unmasked as atypical convolutes of hairy cells.

We describe a patient who concomitantly presented with renal cell carcinoma (RCC) and hairy cell leukemia (HCL). Hairy cells formed atypical cell convolutes on bone marrow smears that might have been mistaken for tumor metastases.

Prospective monitoring of minimal residual disease in acute myeloid leukemia with inversion(16) by CBFbeta/MYH11 RT-PCR: implications for a monitoring schedule and for treatment decisions.

Minimal residual disease in patients with acute myeloid leukemia (AML) with inversion(16) can be monitored by CBFbeta/MYH11 RT-PCR. While the association between molecular remission (MR) in bone marrow (BM) and peripheral blood (PB) and long-term clinical remission (CR) seems to be established, there are insufficient data on the kinetics of CBFbeta/MYH11. We have performed a prospective study in order to generate a reasonable and sufficient schedule for PCR-monitoring. 11 patients with AML and inversion (16) in complete hematological remission have been prospectively monitored by CBFbeta/MYH11 RT-PCR in their BM and PB during an observation period of 7 to 67 months (median 32 months). Patients were followed during consolidation chemotherapy with repetitive cycles of high-dose Ara-C and after autologous or allogeneic stem cell transplantation in 2nd CR or refractory AML. MR never coincided with achievement of CR but occurred between 2 and 8 months after hematological remission. All patients in continuous CR were PCR-negative after 1-8 (median 4) months. Two patients relapsed despite MR for 10 to 15 months. Molecular relapse preceded hematological relapse by 3 to 5 months. Three out of four patients who were not in MR after 8 months relapsed. Allogeneic stem cell transplantation was able to eradicate minimal residual disease in 4/4 patients. In 2 patients a temporary reconversion to PCR-positivity was reversed by reduction of immunosuppression. 1 patient did not become PCR-negative until compete withdrawal of immunosuppression. We suggest that BM and PB should be examined after the last consolidation treatment. In case of MR, PB should be examined every 1 to 2 months and BM examination should be done only in case of PCR-positivity in PB in order to confirm the molecular relapse and to identify an impending cytogenetic and/or hematological relapse. CBFbeta/MYH11 RT-PCR monitoring is able to predict relapse 3 to 5 months prior to overt hematological relapse, offers a window of opportunity for preemptive therapy of molecular relapse and confers implications for immunotherapy in the setting of allografting.