Marrow fibrosis, indicator of therapy failure in chronic myeloid leukemia - prospective long-term results from a randomized-controlled trial

Marrow fibrosis (MF) has rarely been considered in therapy studies on chronic myeloid leukemia (CML), and there is a lack of long-term observations on the basis of sequential bone marrow biopsies (BMBs) taken prospectively during the course of disease. A total of 848 BMBs from 400 patients with Ph(+) CML recruited in the German randomized CML study I were examined for MF before and during therapy. In total, 110 patients had been randomized to receive interferon (IFN)-alpha, and 290 to receive chemotherapy (hydroxyurea (HU): 154, busulfan: 136). During IFN-alpha and HU medication, MF was reduced or did not increase for about 2 years. Evolving or progressive MF was an independent and early predictor of therapy failure about 2 years earlier than indicated by changes in the peripheral blood, spleen size, marrow blast count and cytogenetics (P<0.00005), resulting in a significant shortening of the survival times of patients independent of the type of therapy applied including allografting (multivariate analyses; P<0.00005). The analyzed long-term observations strongly indicate that MF is an independent poor prognostic complication of CML, allowing an early prediction of therapy failure. Consideration of the fiber content in marrow may therefore significantly improve the prediction of therapy efficacy and outcome of disease.

A prospective, randomised, phase II study of horse antithymocyte globulin vs rabbit antithymocyte globulin as immune-modulating therapy in patients with low-risk myelodysplastic syndromes

Immunosuppression has recently been proposed for low-risk myelodysplastic syndromes (MDS) to reverse bone marrow failure by inhibiting intramedullary secretion of proapoptotic cytokines. We treated 35 MDS patients (24 refractory anaemia (RA), 10 RA with excess blasts and one chronic myelomonocytic leukaemia) with either horse antithymocyte globulin 15 mg/kg/day or rabbit antithymocyte globulin 3.75 mg/kg/day, each for 5 days. Median age was 63 years (range: 41-75). After 1 to 34+ months of follow-up (mean: 15+), four patients experienced complete haematological responses (CR), six good responses (GR) and two minor responses. All CRs and GRs occurred in patients with RA, in whom both horse and rabbit ATG yielded five responses out of 12 (42%). Time to response varied between 1 and 10 (mean: 3) months. The median duration of response was 9+ (1-17+) months; five patients are in continuing response. In all, 23 patients suffered side effects > degrees II WHO (the degree of toxicity encountered according to the internationally accepted WHO toxicity grading); one patient died 2 weeks after rabbit ATG from rhinocerebral mucormycosis. Parameters that correlated with response were duration of disease and RA subgroup. In our experience, immune-modulating therapy with either horse or rabbit ATG is feasible in patients with RA and short duration of disease.

Chronic myeloid leukemia in the elderly: long-term results from randomized trials with interferon alpha

Chronic myeloid leukemia (CML) in older patients has not been studied well. To assess the long-term outcome of older patients with Philadelphia- and/or BCR-ABL-positive CML, 199 patients aged >/=60 years representing 23% of 856 patients enrolled in the German randomized CML-studies I (interferon alpha (IFN) vs hydroxyurea (HU) vs busulfan (BU) and II (IFN+HU vs HU alone) were analyzed after a median observation time of 7 years. In all, 45 patients were treated with Bu, 63 with HU, and 91 with IFN. The 5-year survival was 38% in patients >/=60 years and 47% in patients <60 years (P<0.001). Whereas 5-year survival in chemotherapy-treated older patients was inferior to that in younger patients (33 vs 46%, P=0.006 for HU and 29 vs 38%, P=0.042 for Bu), no significant survival difference could be verified in IFN-treated patients (46 vs 53%, P=0.077). Calculation of age-adjusted, relative survival confirmed these results. Adverse effects of IFN were similar in both age groups, but IFN dosage to achieve treatment goals was lower in older patients. We conclude that the course of CML is not different in the elderly. They require lower IFN doses, achieve the same hematologic and cytogenetic response rates and the same survival advantage at comparable toxicity.

Randomized comparison of interferon alpha and hydroxyurea with hydroxyurea monotherapy in chronic myeloid leukemia (CML-study II): prolongation of survival by the combination of interferon alpha and hydroxyurea

The optimum treatment conditions of interferon (IFN) alpha therapy in chronic myeloid leukemia (CML) are still controversial. To evaluate the role of hydroxyurea (HU) for the outcome of IFN therapy, we conducted a randomized trial to compare the combination of IFN and HU vs HU monotherapy (CML-study II). From February 1991 to December 1994, 376 patients with newly diagnosed CML in chronic phase were randomized. In all, 340 patients were Ph/BCR-ABL positive and evaluable. Randomization was unbalanced 1:2 in favor of the combination therapy, since study conditions were identical to the previous CML-study I and it had been planned in advance to add the HU patients of study I (n=194) to the HU control group. Therefore, a total of 534 patients were evaluable (226 patients with IFN/HU and 308 patients with HU). Analyses were according to intention-to-treat. Median observation time of nontransplanted living patients was 7.6 years (7.9 years for IFN/HU and 7.3 years for HU). The risk profile (new CML score) was available for 532 patients: 200 patients (38%) were low, 239 patients (45%) intermediate, and 93 patients (17%) high risk. Complete hematologic response rates were higher in IFN/HU-treated patients (59 vs 32%). Of 169 evaluable IFN/HU-treated patients (75%), 104 patients (62%) achieved a cytogenetic response that was complete in 12% (n=21), major in 14% (n=24), and at least minimal in 35% (n=59). Of the 534 patients, 105 (20%) underwent allogeneic stem cell transplantation in first chronic phase. In the low-risk group, 65 of 200 patients were transplanted (33%), 30 (13%) in the intermediate-risk group, and nine (10%) in the high-risk group. Duration of chronic phase was 55 months for IFN/HU and 41 months for HU (P<0.0001). Median survival was 64 months for IFN/HU and 53 months for HU-treated patients (P=0.0063). We conclude that IFN in combination with HU achieves a significant long-term survival advantage over HU monotherapy. In view of the data of CML-study I, these results suggest that IFN/HU is also superior to IFN alone. HU should be combined with IFN in IFN-based therapies and for comparisons with new therapies.

Non-infectious lung complications are closely associated with chronic graft-versus-host disease: a single center study of incidence, risk factors and outcome

Non-infectious lung complications (NILC) are frequent, influencing morbidity and mortality of patients after allogeneic BMT. Although the term NILC encompasses a number of different entities, an association with GVHD has been noted for almost all of them. Our study was directed towards assessing the incidence and risk factors for developing NILC, as well as the response to treatment and long-term outcome. Forty (14.7%) out of 272 patients surviving for more than 3 months after allogeneic BMT, developed lung complications fulfilling the criteria for NILC. The evaluation was based on clinical investigation, radiologic imaging, lung function tests, broncho-alveolar lavage and biopsies. Risk factors were assessed by univariate and multiple statistical regression models, where chronic GVHD proved to be the only significant risk factor for the development of NILC (P = 0.011). In three patients NILC developed in direct association with donor lymphocyte infusions. The majority of patients responded well to treatment with corticosteroids and immunosuppressive drugs. NILC had no adverse effect on survival. The frequency of NILC was low in autologous (5%) as compared with allogeneic transplants (14.7%) but this difference was not statistically significant. Bone Marrow Transplantation (2000) 25, 1263-1268.

Paroxysmal nocturnal haemoglobinuria: a replacement of haematopoietic tissue?

Acquired somatic mutations of the PIG-A gene lead to deficient expression of glycosyl-phosphatidyl-inositol-anchored proteins (GPI-AP) by haematopoietic cells and play a causative role in the pathogenesis of paroxysmal nocturnal haemoglobinuria (PNH). However, PIG-A mutations do not explain how the defective PNH clone can expand. It was hypothesized that a selection process conferring a relative advantage to the GPI-AP-deficient population is required. Since GPI-AP-deficient cells are also detectable in a substantial proportion of patients with otherwise typical aplastic anaemia (AA), the mechanisms inducing bone marrow failure might selectively spare the GPI-deficient cells. In order to examine the growth characteristics of GPI-AP-deficient cells in more detail, we performed repeated analyses of GPI-AP expression on peripheral blood cells in 41 patients with AA. We observed four patterns of the course of GPI-AP-deficient populations: (1) 13 patients showed normal expression of GPI-AP in the first analysis and in at least two follow-up studies at a median time of 709 days after the first analysis. (2) Secondary evolution of a GPI-AP-deficient population was a rare event. Only 4 patients with initially normal GPI-AP expression developed a GPI-AP-deficient population during follow up after immunosuppressive treatment. (3) Persistence of GPI-AP-deficient cells was observed in 16 patients during a median follow-up time of 774 days. However, in some patients, the size of the GPI-AP-deficient population increased substantially. (4) Disappearance of a GPI-AP-deficient population was observed in 8 patients. The time course of GPI-AP expression in relation to the treatment suggests that therapeutic interventions might modulate the ratio of normal versus GPI-AP-deficient haematopoiesis. Overall, these data argue against an 'absolute growth advantage' of GPI-AP-deficient cells. Our data are consistent with the hypothesis that haematopoietic failure caused by damage to normal haematopoiesis allows the outgrowth of a GPI-AP-deficient population. Thus, in at least some patients GPI-AP-deficient cells might pre-exist at a very low percentage and replace haematopoiesis after an insult to the normal cells.

Aplastic anemia before bone marrow transplantation and antilymphocyte globulin

In severe aplastic anemia, disease-dependent mortality was high before allogeneic bone marrow transplantation (BMT) and immunosuppressive therapies (IST) including antilymphocyte globulin became available. However, under supportive therapy alone, spontaneous remissions were observed in up to 20% of severe cases, reflecting the natural course of the disease. Therefore, in evaluating new forms of treatment, one has to keep in mind that remission is not necessarily response, and that final proof of utility of any new therapy still requires a randomized study design. Transition to leukemia or myelodysplasia was rarely observed if the initial diagnosis was accurate. The much higher incidence of leukemias in patients treated by IST, but not by BMT is probably due to the better life expectancy of patients at risk, rather than to a leukemogenic potential of IST itself. 'Outdated' therapeutic modalities, such as androgens or splenectomy, may still be justified as an adjuvant therapy in selected cases.

Geographic distribution of CDA-II: did a founder effect operate in Southern Italy?

BACKGROUND AND OBJECTIVE

Congenital dyserythropoietic anemia type II (CDA-II) is an autosomal recessive condition, whose manifestations range from mild to moderate. Its exact prevalence is unknown. Based on a recently established International Registry of CDA-II (64 unrelated kindreds), a high frequency of CDA II families living in South Italy became evident.

DESIGN AND METHODS

The aim of this study was to define the haplotypes of the CDA II kindreds living in Southern Italy based on markers D20S884, D20S863, RPN, D20S841 and D20S908. These markers map to 20q11.2, within the interval of the CDAN2 gene that is responsible for CDA II. Next, we looked at these markers in kindreds from other regions of Italy and from other countries, with special attention to families having ancestors in Southern Italy.

RESULTS

Evaluation of the geographic distribution of the ancestry of Italian CDA-II patients clearly demonstrated the unusually high incidence of this condition in Southern Italy. Our statistical calculations and linkage disequilibrium data also clearly demonstrate a strong association of the markers of chromosome 20 with the disease locus in our sample. Almost all the regions defined by the markers here used is in disequilibrium with the disease. Combining the data from the Italian sample together with those obtained from the non-Italian ones, we can restrict the area of highest disequilibrium to that defined by markers D20S863-D20S908.

INTERPRETATION AND CONCLUSIONS

Despite the presence of this linkage disequilibrium the search for a common haplotype failed. This could suggest that the mutation was very old or that it occurred more than once on different genetic backgrounds.

Serum erythropoietin and thrombopoietin levels in patients with essential thrombocythaemia

In 40 patients with essential thrombocythaemia (ET) serum erythropoietin (EPO) and thrombopoietin (TPO) concentrations were determined and compared with the EPO and TPO values of a healthy control group. The mean EPO serum concentration for 24 control patients was 9.4 mU/ml +/- 3.7 (range 2-17.9), for 32 untreated ET patients at diagnosis 6.6 mU/ml +/- 7.6 (range 0.5-44.3) and for 8 ET patients treated with cytoreduction 14.1 mU/ml +/- 8.0 (range 4.5-26.1). Serum EPO levels in untreated ET patients at diagnosis were significantly lower compared with serum EPO levels in healthy control patients (p=0.002). Serum EPO levels in treated ET patients were not different from serum EPO levels in healthy controls (p=0.13) but were significantly higher compared with untreated ET patients (p=0.003). Serum TPO levels were determined in 18 of 40 ET patients, the mean TPO serum concentration was 211 pg/ml +/- 109 (range 62,5-345). The mean TPO serum concentration for 10 untreated ET patients at diagnosis was 162 pg/ml +/- 87 (range 62,5-302) and for 8 ET patients who had received cytoreductive treatment 272 pg/ml +/- 106 (range 96-345), respectively (p=0.04). Both serum TPO levels for treated and untreated ET patients were significantly higher (p<0.001) compared with serum TPO levels for healthy controls. The results of our study suggest a difference in the regulation of serum EPO and TPO in patients with ET. While the mean serum EPO level is decreased in untreated ET patients, the corresponding mean serum TPO level is increased. Treatment with cytoreduction, results in normalisation of the mean serum EPO level, whereas the mean TPO serum level remains elevated.

Interferon-alpha before allogeneic bone marrow transplantation in chronic myelogenous leukemia does not affect outcome adversely, provided it is discontinued at least 90 days before the procedure

The influence of interferon-alpha (IFN) pretreatment on the outcome after allogeneic bone marrow transplantation (BMT) in chronic myelogenous leukemia (CML) is controversial. One goal of the German randomized CML Studies I and II, which compare IFN +/- chemotherapy versus chemotherapy alone, was the analysis of whether treatment with IFN as compared to chemotherapy had an influence on the outcome after BMT. One hundred ninety-seven (23%) of 856 Ph/bcr-abl-positive CML patients were transplanted. One hundred fifty-two patients transplanted in first chronic phase were analyzed: 86 had received IFN, 46 hydroxyurea, and 20 busulfan. Forty-eight patients (32%) had received transplants from unrelated donors. Median observation time after BMT was 4.7 (0.7 to 13.5) years. IFN and chemotherapy cohorts were compared with regard to transplantation risks, duration of treatments, interval from discontinuation of pretransplant treatment to BMT, conditioning therapy, graft-versus-host disease prophylaxis and risk profiles at diagnosis and transplantation, and IFN cohorts also with regard to performance and resistance to IFN. Outcome of patients receiving related or unrelated transplants pretreated with IFN, hydroxyurea, or busulfan was not significantly different. Five-year survival after transplantation was 58% for all patients (57% for IFN, 60% for hydroxyurea and busulfan patients). The outcome within the IFN group was not different by duration of prior IFN therapy more or less than 5 months, 1 year, or 2 years. In contrast, a different impact was observed in IFN-pretreated patients depending on the time of discontinuation of IFN before transplantation. Five-year survival was 46% for the 50 patients who received IFN within the last 90 days before BMT and 71% for the 36 patients who did not (P =.0057). Total IFN dosage had no impact on survival after BMT. We conclude that outcome after BMT is not compromised by pretreatment with IFN if it is discontinued at least 3 months before transplantation. Clear candidates for early transplantation should not be pretreated with IFN.

Aetiology and clinical significance of thrombocytosis: analysis of 732 patients with an elevated platelet count

OBJECTIVE

To determine the aetiology and clinical significance of an elevated platelet count (thrombocytosis) in a large cohort of patients.

DESIGN

A retrospective review of the medical records was performed on all patients, who had at least one platelet count > or = 500 x 10(9) L-1.

SETTING

Departments of Medicine and Surgery, University of Ulm, Germany.

SUBJECTS

A total of 732 patients with thrombocytosis.

MAIN OUTCOME MEASURES

Classification of thrombocytosis and thromboembolic complications, and evaluation of laboratory parameters distinguishing between primary and secondary thrombocytosis.

RESULTS

Of the total of 732 patients, 89 (12.3%) had primary and 643 (87.7%) had secondary thrombocytosis. Essential thrombocythaemia was observed in 40 of 89 patients (45%) with primary thrombocytosis. The most frequent causes of secondary thrombocytosis were tissue damage (42%), infection (24%), malignancy (13%) and chronic inflammation (10%). Primary thrombocytosis was significantly associated with a higher platelet count and an increased incidence of both arterial and venous thromboembolic complications. In secondary thrombocytosis, thromboembolic events were restricted to the venous system and occurred only in the presence of other risk factors. Mean values of leucocyte count, haematocrit, erythrocyte sedimentation rate, fibrinogen, serum potassium and lactate dehydrogenase were significantly different in primary and secondary thrombocytosis.

CONCLUSIONS

The finding of an elevated platelet count on routine blood examination has diagnostic, prognostic and therapeutic implications. It is of clinical importance to distinguish between primary and secondary thrombocytosis, as thrombotic complications occur more frequently in primary thrombocytosis. Unless additional risk factors are present, secondary thrombocytosis is not associated with a significant risk for thromboembolic events.

High levels of thrombopoietin in sera of patients with essential thrombocythemia: cause or consequence of abnormal platelet production?

Thrombopoietin (TPO) is the most important regulator of megakaryocyte development and platelet production. Platelet production is thought to be regulated by a negative regulatory feed back loop. In an attempt to evaluate the role of TPO in the pathobiology of essential thrombocythemia (ET), we have examined levels of TPO and other cytokines with thrombopoietic activity (interleukin-6 and interleukin-11) in sera obtained from 25 patients with ET (ten treated, 15 untreated) and 117 healthy control subjects. TPO serum levels were assessed using a sandwich-antibody ELISA that utilizes a polyclonal rabbit antiserum for both capture and signal. The mean serum TPO level in 25 ET patients was significantly elevated (545+/-853 pg/ml) as compared with that in healthy controls (95.3+/-54.0 pg/ml,p<0.001). The difference in TPO serum levels between ten treated (781+/-1229 pg/ ml) and 15 untreated ET patients (388+/-458 pg/ml) did not reach statistical significance (p = 0.09). We conclude that either consumption or production of TPO is altered in ET. Failure of appropriate feedback regulation and continued megakaryocyte stimulation by an elevated TPO may play an important role in the pathobiology of ET.

Chronic myeloid leukemia in accelerated phase: treatment results with conventional chemotherapy and allogeneic bone marrow transplantation in 96 patients

The treatment results of 96 patients with Philadelphia-positive chronic myeloid leukemia (CML) in accelerated phase (AP) were reviewed retrospectively. Treatment of AP consisted of allogeneic bone marrow transplantation in 20 (14 related and 6 unrelated donors) or conventional chemotherapy (CC) in 76 patients. Three main treatment strategies were followed in the CC group: continuation (group A) or dose escalation (group B) of chronic phase therapy or change of chronic phase therapy to hydroxyurea (group C). Median survival was 7.0 months in group A (range 1.8-110), in group B 8.3 months (range 0.9-40) and in group C 9.6 months (range 1.5-47.6), p=0.89. Survival in CC was dependent on response to therapy as the achievement of a second chronic phase was significantly associated (p<0.001) with a longer median survival (21 months) compared with stable accelerated phase disease (11 months) or treatment failure (5 months). Median survival in the BMT group was 16.7 months (range 5-77), the 5-yr probability of relapse was 25% and the 5-yr disease-free survival was 36%. For patients <55 yr median survival after BMT was significantly prolonged compared with median survival after CC (n=45, 8.3 months, p=0.008). After developing criteria of AP, median survival in our analysis has been less than 1 yr. The results of conventional chemotherapy in the treatment of accelerated phase CML are disappointing. If a suitable donor is available allogeneic BMT should be performed without delay in patients with AP.

Survival with bone marrow transplantation versus hydroxyurea or interferon for chronic myelogenous leukemia. The German CML Study Group

Hydroxyurea, interferon, and HLA-identical sibling bone marrow transplantation are common therapies for chronic myelogenous leukemia (CML) in chronic phase. Which is best is controversial. The purpose of this study was to compare survival of patients with CML receiving HLA-identical sibling transplants versus hydroxyurea or interferon. The transplant cohort included 548 recipients of HLA-identical sibling transplants, reported to the International Bone Marrow Transplant Registry. The nontransplant cohort included 196 patients receiving hydroxyurea (n = 121) or interferon (n = 75) on a randomized trial of the German CML Study Group. Survivals were compared using proportional hazards regression with fixed and time-dependent variables to adjust for patient differences and changing risks over time. For the first 18 months after diagnosis, mortality was higher in the transplant than the nontransplant cohort (relative risk [RR], 5.85; P < .0001). From 18 to 56 months, mortality was similar (RR, 0.80; P = .38). After 56 months, mortality was lower in the transplant cohort (RR, 0.16; P < .0001). Seven-year survival probabilities (95% confidence interval) were 58% (50% to 66%) with transplant and 32% (22% to 41%) with hydroxyurea or interferon. There was a significant survival advantage for hydroxyurea or interferon in the first 4 years after diagnosis and for transplants starting 5.5 years after diagnosis. For transplants done within 1 year of diagnosis, the survival advantage for transplantation began earlier. Survival advantage for transplants was greater and occurred earlier in patients with intermediate- and high-risk prognostic features than in those with low-risk features. This study confirms higher early mortality, but a long-term survival advantage for HLA-identical sibling transplants over hydroxyurea or interferon in CML.

Thrombopoietin serum levels in patients with aplastic anaemia: correlation with platelet count and persistent elevation in remission

In an attempt to evaluate the role of thrombopoietin (TPO) in the pathobiology of aplastic anaemia (AA), we have examined TPO levels in sera from 54 AA patients and 119 healthy controls. A total of 92 samples were collected from AA patients: 43 samples were harvested at diagnosis, 23 samples in the cytopenic period after treatment, and 26 samples when patients were in partial (n=10) or complete remission (n=16) following immunosuppressive treatment. TPO serum levels were assessed by a sandwich-antibody ELISA that utilized a polyclonal rabbit antiserum for both capture and signal. Serum samples from normal donors revealed a mean TPO level of 95.3 +/- 54.0 pg/ml (standard deviation). Mean TPO levels in AA sera collected at diagnosis and before onset of treatment were 2728 +/- 1074 pg/ml (P<0.001 compared to normal controls: mean platelet count at that time: 27x10(9)/l). TPO serum levels of AA patients in partial or complete remission after immunosuppressive treatment were significantly lower than TPO levels at diagnosis (P<0.001). However, despite normal platelet counts (mean 167x10(9)/l), TPO levels remained significantly elevated in complete remission (mean TPO 1009 +/- 590 pg/ml, P<0.001 compared to normal controls). There was a significant inverse correlation between serum TPO levels and platelet counts in AA patients who were not transfused for at least 2 weeks prior to sample collection (coefficient of correlation (r) = -0.70, P<0.0001). In summary, TPO levels were highly elevated in sera of patients with AA. Thus there is no evidence to suggest an impaired TPO response contributing to thrombocytopenia in AA. Thrombopoietin did not return to normal levels in remission, indicating a persisting haemopoietic defect in remission of AA. We hypothesize that elevated levels of TPO may be required to maintain normal or near normal platelet counts in remission of AA.

[Leukocyte transfusion as therapy of recurrent CML after allogenic bone marrow transplantation]

Eight patients with relapsed chronic myelogenous leukemia (CML) after allogeneic bone marrow transplantation (BMT) were treated with alpha-interferon and leukocyte transfusions of the bone marrow donor. Six patients responded with disappearance of leukemic cells (Ph1, BCR-ABL) and reestablished donor hemopoiesis. All six patients developed bone marrow hypoplasia and graft-versus-host disease (GvHD). Three of the six patients died of cerebral bleeding, infection and GvHD, respectively. The remaining three patients are alive and well at day 418, 677, 818 after leukocyte transfusions. Two patients relapsed with more advanced disease of CML after BMT and failed treatment. Donor leukocyte transfusions provide an effective therapy for patients with relapsed CML after BMT, but are associated with a high mortality due to bone marrow hypoplasia and GvHD.

Rearranged Ig heavy chain DNA is detectable in cell-free blood samples of patients with B-cell neoplasia

Tumor-derived DNA has been shown in various cell-free body fluids. In this study, soluble tumor-derived DNA was analyzed in serum and plasma samples of patients with B-cell malignancies. DNA was extracted from tumor cell specimens as well as serum and plasma samples collected from 110 patients with non-Hodgkin's lymphoma and acute B-precursor lymphoblastic leukemia and was subjected to polymerase chain reaction (PCR) analysis for rearranged immunoglobulin heavy chain DNA. In 54% of serum or plasma samples analyzed at different times before and during treatment, clonal DNA from a rearranged immunoglobulin heavy chain locus was detectable. When examined at diagnosis and before any treatment, clonotypic DNA was found in serum or plasma of 86% of the patients. Serum or plasma from patients with systemic or bulky disease was uniformly PCR positive, whereas clonotypic DNA was also recovered from the serum or plasma from the majority of patients with limited disease stages. Degradation of clonal DNA by nucleases in vitro was shown to be one cause of false-negative PCR results. This technical drawback can be relieved by adding a nuclease inhibitor like EDTA, ie, by using plasma instead of serum for PCR analysis. Treatment of patients with cytotoxic drugs was followed by rapid clearance of DNA from the peripheral blood, suggesting that soluble tumor-derived DNA might be associated with viable and proliferating tumor cells. Follow-up studies showed a close correlation of persisting soluble tumor-derived DNA with resistant disease or early relapse. In summary, these data suggest that tumor-derived DNA can be detected in serum or plasma of the majority of patients with B-cell malignancies and that testing of serum or plasma for tumor-associated DNA may be a novel parameter for monitoring response to treatment.