Prognostic factors affecting the outcome after allogeneic haematopoietic stem cell transplantation for myelodysplastic syndrome

In the present study, we retrospectively analysed the results of HSCT in 47 consecutive patients with MDS diagnosed at our department between 2002 and 2019, with a focus on possible predictive factors influencing overall survival (OS), the development of relapse, infections, and the occurrence of graft versus host disease (GvHD). In a univariate analysis, the pre-transplantation value of blasts in the marrow < 5% (p = 0.006), the revised International Prognostic Scoring System (IPSS-R) (p = 0.041), and karyotype (p = 0.009) were predictive of OS. Neither the elevation of serum ferritin (> 1000 ug/ml) nor increased C-reactive protein (CRP) (> 5 mg/l) was associated with shorter OS. In contrast, elevated serum lactate dehydrogenase (LDH) (> 213 U/l) was associated with shorter OS (p = 0.04).

Management of chronic lymphocytic leukemia (CLL) in the elderly: a position paper from an international Society of Geriatric Oncology (SIOG) Task Force

Chronic lymphocytic leukemia (CLL) mainly affects older people: the median age at diagnosis is > 70 years. Elderly patients with CLL are heterogeneous with regard both to the biology of their disease and aging. Following the diagnosis of CLL in an elderly individual, careful risk assessment is essential when treatment options are evaluated. This includes not only clinical staging and evaluation of disease-specific prognostic biomarkers such as 17p deletion and TP53 mutation, but also of comorbidities, physical capacity, nutritional status, cognitive capacity, ability to perform activities of daily living and social support. Comorbidity scoring and geriatric assessment tools are helpful in achieving such multidimensional evaluation in a systematic manner. The introduction of new drugs including novel monoclonal antibodies and kinase inhibitors offers enhanced opportunities for the treatment of elderly patients with CLL. This position paper of a Task Force of the International Society of Geriatric Oncology (SIOG) reviews currently available evidence relevant to such patients. All types of elderly patient (i.e. chronological age > 65-70 years) are considered, from robust (fit) to vulnerable (unfit) to the terminally ill. Among the topics covered are the following: (i) the relationship between chronological age, prognosis and survival, (ii) assessment of biological aging, (iii) biological age as a determinant of treatment feasibility and tolerance and (iv) tailoring of both first and further-line treatment to the circumstances of the individual patient.

[Therapeutic Options for "Slow go" Patients with Chronic Lymphocytic Leukemia]

Chronic lymphocytic leukemia is a disease of older patients, most of them suffering from significant comorbidities or functional limitations (so -called 'slow- go' patients). Unfortunately, clinical trials in chronic lymphocytic leukemia have until recently focused mainly on the subgroup of younger patients in good overall condition ('go- go' patients). Clinico- biological parameters, such as performance status, calculated creatinine clearance, the number and severity of comorbidities along with individual clinical assessment can help guide decisions relating to the objectives and ultimately the intensity of treatment. Two large randomized studies have recently demonstrated that the addition of monoclonal antibodies against CD20 (obinutuzumab, rituximab and ofatumumab) to chlorambucil in untreated 'slow- go' patients resulted in a significant increase in the number of complete remissions, progression-free survival and even overall survival (for obinutuzumab and rituximab) with an acceptable safety profile. Chemoimmunotherapy combining chlorambucil with anti-CD20 antibody is thus the new standard 1st line therapy in this group of patients. Treatment of relapsed/ refractory chronic lymphocytic leukemia in 'slow- go' patients is very difficult and specific data is sparse. In this indication, we have witnessed an extraordinary breakthrough by means of small oral inhibitors interfering with B -cell receptor downstream signaling pathways: ibrutinib, the Brutons tyrosine kinase inhibitor, and idelalisib, the inhibitor of phosphatidylinositol 3- kinase δ. Both drugs radically changed the approach to the treatment of relapsed/ refractory chronic lymphocytic leukemia; relatively mild toxicity also predetermines their use in elderly/ comorbid patients. Other treatment options for relapsed/ refractory chronic lymphocytic leukemia in this subgroup include alemtuzumab, ofatumumab, high-dose glucocorticoids + anti-CD20 antibodies, or bendamustine + rituximab regimen. This review summarizes current data regarding the treatment of elderly and comorbid patients with chronic lymphocytic leukemia.

Prognostic relevance of angiopoietin-2, fibroblast growth factor-2 and endoglin mRNA expressions in chronic lymphocytic leukemia

Elevated levels of circulating angiogenic cytokines and increased expression of genes encoding angiogenic factors have been reported in recent years in patients with chronic lymphocytic leukemia (CLL) but data regarding prognostic and predictive significance are still limited. Therefore, in the present study based upon our prior pilot results, we measured mRNA expressions of angiopoietin-2 (Ang-2), fibroblast growth factor-2 (FGF-2) and endoglin (CD105) by reverse transcription quantitative PCR in purified CD19+ cells from 70 untreated CLL patients (median age, 63 years; males, 64%; Rai III/IV stages, 29 %; unmutated IgVH genes, 60 %) and evaluated their possible association with established prognostic factors and clinical course of the disease. Higher expression of Ang-2 was significantly associated with unmutated IgVH genes (n = 55, p = 0.003). Higher CD105 expression was significantly associated with unmutated IgVH genes (n = 55, p < 0.001), high CD38 expression (n = 66, p = 0.022), high ZAP-70 expression (n = 66, p = 0.010), Rai stage I-IV (n = 70, p < 0.001), progressive clinical course of CLL (n = 70, p = 0.001) and shorter time to treatment (n = 70; p < 0.001). Expression of FGF-2 was not significantly associated with any of the prognostic markers. These results indicate that elevated expression of Ang-2 and in particular CD105 by CLL cells is associated with unfavorable prognostic features and clinical outcome; thus, both cytokines appear to play an important role in biology and progression of CLL and warrant further investigation.

[Assessment of selected markers of apoptosis and angiogenesis in chronic lymphocytic leukemia]

INTRODUCTION

Search for new prognostic markers in order to improve prognostic accuracy and predict clinical outcome at the time of dia-gnosis has recently become one of the major trends in chronic lymphocytic leukemia (CLL). PATIENTS AND METHODS, AIM OF STUDY: The aim of our study was assessment of selected markers of apoptosis and angiogenesis and their potential as new prognostic factors. We evaluated serum levels of tumor necrosis factor α (TNFα) and transforming growth factor β 1 (TGFβ1) using commercially available enzyme linked immunosorbent assay; furthermore, we quantified expression of type II receptor for transforming growth factor beta (TGFβRII) and type 2 receptor for fibroblast growth factor 2 (FGFR2) on CLL cells using flow cytometry analysis in 75 previously untreated patients with CLL (47 males and 28 females, median age, 65 years, range 38- 82) and healthy donors.

RESULTS

We found significantly elevated TNFα in patients with CLL compared to the control group (p < 0.0001); high expression of TNFα was associated with unfavourable prognosis: significantly higher concentrations were found in patients with Rai highrisk group compared to low and intermediate-risk group (p = 0.0008 and p = 0.0097), with high serum β2- microglobulin (p = 0.045), massive lymphadenopathy (p = 0.0083), unmutated genes for variable region of immunoglobulin heavy chain (IgVH) (p = 0.041) and unfavourable cytogenetic aberrations (p = 0.0014). In addition, patients with progressive CLL had significantly higher TNFα than those with stable clinical course (p = 0.0009); time to treatment was significantly shorter in patients with higher TNFα (p = 0.0049). Higher TGFβ1 concentrations were associated with favourable subgroups: with Rai low  risk group compared to high risk group (p = 0.011), patients without massive lymphadenopathy (p = 0.041), patients with mutated IgVH (p = 0.012) and ZAP 70 negativity (zeta associated protein of 70 kilodaltons) (p = 0.044). Patients with progressive CLL had significantly lower TGFβ1 levels than those with stable course (p = 0.0014) and time to treatment was significantly longer in patients with higher TGFβ1 (p = 0.016). Patients with Rai high risk group had significantly lower TGFβRII expression than those with low  risk group (p = 0.022). The prognostic significance of FGFR2 was not found. Significant and independent prognostic factors for overall survival were high serum concentrations of TNFα and massive lymphadenopathy (p = 0.036, resp. p = 0.047).

CONCLUSION

Based on our results, TNFα and TGFβ1 possess prognostic significance in CLL; further research in this direction may also be important therapeutically, because these signal pathways could serve as possible treatment targets.

[Our experience with the treatment of primary lymphomas of the central nervous system]

INTRODUCTION

The aim of this study was to assess treatment efficiency, overall survival (OS) and identify risk factors with the influence on patients prognosis in patients with primary central nervous system lymphomas (PCNSL) who were treated with intensive chemotherapy based on high-dose methotrexate and cytosin-arabinoside followed by whole-brain radiotherapy (MPV regimen).

PATIENTS AND METHODS

From January 1998 to February 2011, 39 patients with PCNSL were diagnosed on our department. The median from the first clinical symptomatology to histological diagnosis was 4 weeks (range, 2-19). Thirty-seven patients were treated with MPV regimen.

RESULTS

The therapeutic response was evaluated in 35 patients (2 patients died early during treatment). The overall response/complete remission rate was 63/60%. At the time of analysis (november 2011), the median of follow-up was 16,5 months; 31 patients died (the most often causes of death were poor treatment effect and treatment complications). The 2-year OS was 30% and median PFS and OS were 9 and 12 months. Patients with WHO performance status 0-1 and those with normal serum lactate dehydrogenase serum had significantly longer OS (p = 0.0495 and p = 0.0232).

CONCLUSION

The treatment results of our patients appear to be inferior than data from literature. The reason is probably high occurrence of negative prognostic factors. Early diagnosis and intensive treatment are crucial for improvement of prognosis.

Pitfalls and limitations of ZAP-70 detection in chronic lymphocytic leukemia

Zeta-associated protein of 70 kDa (ZAP-70) is a tyrosine kinase that plays a role in signal transduction from the T-cell receptor. ZAP-70 is expressed in normal T-cells and NK-cells. Increased expression of ZAP-70 has been identified in chronic lymphocytic leukemia (CLL). CLL patients with increased ZAP-70 expression have significantly worse prognosis in terms of both progression-free survival and overall survival. There are several methods to quantify ZAP-70: polymerase chain reaction (PCR), immunoblotting, immunohistochemistry, and flow cytometry. Use of flow cytometry for ZAP-70 detection seems to be advantageous as this technique enables us to assess the presence of ZAP-70 separately on CLL clone, T-cells, and NK-cells. On the other hand, detection of ZAP-70 by flow cytometry is substantially influenced by many variables. The principal drawback of flow cytometry is the absence of consensus regarding selection of optimal anti-ZAP-70 antibody, fluorochrome conjugate, the most reliable staining technique, and optimal positivity threshold. This article summarizes pitfalls of flow cytometric analysis of ZAP-70 in CLL.

[Guidelines for alemtuzumab treatment in chronic lymphocytic leukaemia (CLL)]

Alemtuzumab, the humanized monoclonal anti-CD52 antibody, is an effective agent in the treatment of fludarabine-refractory chronic lymphocytic leukemia (CLL). Due to many specific issues associated with alemtuzumab treatment, the Working Committee of Czech CLL Study Group developed these guidelines.

SUMMARY OF RECOMMENDATIONS

(1) The main indication of alemtuzumab is fludarabine-refractory CLL. (2) Further possible indications include first-line treatment (in patients who cannot be treated by fludarabine-containing regimens), therapy of patients with del 17p, treatment of refractory autoimmune cytopenias and management of patients with severe cytopenias due to bone marrow infiltration. (3) The treatment should last 12 weeks and should not be terminated prematurely if there are no signs of CLL progression; bone marrow aspirate/biopsy can be performed after 12 weeks of treatment. (4) Subcutaneous administration of alemtuzumab seems to be equally effective with advantageous reduction of infusion-related adverse events. (5) Patients treated with alemtuzumab must receive combined antimicrobial prophylaxis against Pneumocystis jiroveci and herpetic viruses. Cytomegalovirus viremia should be monitored using weekly PCR from peripheral blood. (6) Use of alemtuzumab in combinations and consolidation/maintenance protocols must be considered experimental and needs optimization within prospective clinical trials. (7) Alemtuzumab treatment should be conducted by an experienced hematologist within a center of intensive hematology care.

[Prognostic markers in chronic lymphocytic leukemia]

Chronic lymphocytic leukemia is the most common leukemia type in Western countries. Even incidence of chronic lymphocytic leukemia is high, this disease remained beyond interest for a very long time. However, in the last few years the view of this disease fundamentally changed and due to intensive study, new knowledge especially on pathogenesis, prognostic factors and therapy based on intensive therapeutic procedures were made. Today we know that usage of classical prognostic factors is insufficient for prognosis evaluation in the individuals. However modern (IgVH mutation status, cytogenetic abberations) and new markers (LPL/ADAM29 ratio, microRNA, markers of angiogenesis etc) have potential to distinguish patients in early stages to groups with significantly different prognosis and predict clinical course of the disease.

[Primary central nervous system lymphomas]

Primary central nervous system lymphoma (PCNSL) is a rare form of extranodal lymphoma (nearly always non-Hodgkin's) and accounts for approximately 3 to 4% of primary brain tumors. PCNSL typically affects patients older than 60 years. Clinical features are variable and reflect the location of central nervous system lesion. Magnetic resonance imaging and stereotactic biopsy are the most important tools for diagnostic assessment. Chemotherapy based on high-dose of methotrexate (HD-MTX) and whole brain radiotherapy are the cornerstones of treatment. Radiotherapy is usually omitted in individuals older than 60 years because of high risk of unacceptable delayed neurotoxicity. Treatment of PCNSL should be started as soon as possible after diagnosis because delay in treatment may shorten the patients' survival.

[Staging of non-Hodgkin's lymphoma--recommendations of the Czech Lymphoma Study Group]

BACKGROUNDS

The Ann Arbor system is typically used for the staging of Non-Hodgkin's lymphomas. This classification was nevertheless originally developed in the 1970s for Hodgkin's lymphoma, a disease usually confined to the lymph nodes with less frequent dissemination to extralymphatic organs/tissues and extremely rare primary extranodal involvement. Non-Hodgkin's lymphomas, however, are more often associated with extralymphatic involvement and primary extranodal lymphomas are relatively common (approximately 1/3 of cases). Therefore, the value of the Ann Arbor staging system appears to be limited in these cases. An analysis of data from centres participating within the Czech Lymphoma Study Group showed that staging of Non-Hodgkin's lymphomas with extranodal involvement is not uniform.

DESIGN

At the end of 2009, a draft for a Non-Hodgkin's lymphomas staging system was put forward for use by the lymphoma register of the Czech Lymphoma Study Group with special regard paid to the involvement of extralymphatic organs/tissues. This draft was further refined following comments from members of the Czech Lymphoma Study Group committee and the final form was accepted at the meeting of the Czech Lymphoma Study Group committee in January 2010.

RESULTS

A consensus was reached at the meeting of the Czech Lymphoma Study Group committee regarding the staging of various combinations of nodal and extranodal involvement. For the purpose of suitable staging and appropriate treatment intensity, extranodal organs were divided into "major"--liver, lungs, bones, mesothelium (pleura, peritoneum, pericardium) and soft tissues. All other organs were defined as "minor".

CONCLUSION

The Ann Arbor staging system is suitable for the staging of Non-Hodgkin's lymphomas with lymph node/lymphatic tissue involvement. As regards the extralymphatic spread of the disease or primary extranodal lymphomas, this classification should rather be adapted to practical needs. The validity of the updated classification system will be assessed in both prospective and retrospective Czech Lymphoma Study Group studies.

Choice of endothelial marker is crucial for assessment of bone marrow microvessel density in chronic lymphocytic leukemia

Angiogenesis is a potential prognostic factor in chronic lymphocytic leukemia (CLL). Elevated circulating levels of angiogenic factors in CLL have been repeatedly reported. Nevertheless, the issue of bone marrow neovascularization in CLL remains controversial, partly due to limited number of published studies, different methods of assessing microvessel density (MVD) and small patient cohorts. Moreover, there are very scarce data regarding the relationship of marrow angiogenesis to prognostic markers in CLL. Our objectives were: 1. To assess bone marrow MVD in CLL using two different monoclonal antibodies and a reproducible method of MVD quantification; 2. To examine the possible association of marrow MVD and clinical course, pattern of marrow infiltration, Rai stage, cytogenetic abnormalities detected by fluorescence in situ hybridization (FISH), and mutation status of immunoglobulin heavy chain variable region (IgVH). MVD was higher using CD34 vs vWF antibody (p<0.0001). However, no MVD differences were detected between CLL subgroups subdivided according to the above-mentioned prognostic factors. In conclusion, MVD assessment using anti-CD34 resulted in higher MVD counts than when using anti-vWF antibody. No association of MVD with any prognostic factors was observed, possibly due to the limited patient cohort. As the need for bone marrow trephine biopsies in CLL is significantly decreasing, a standardized method of neovascularization assessment is required to enable possible multicentre studies in order to conduct larger investigations and thereby shed more light on the real clinical significance of bone marrow angiogenesis in CLL.

[Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) are elevated in peripheral blood plasma of patients with chronic lymphocytic leukemia and decrease after intensive fludarabine-based treatment]

Chronic lymphocytic leukemia (CLL) is characterized by extraordinary heterogeneity in terms of clinical course with overall survival ranging from several months to dozens of years. It is currently not possible to accurately predict the future clinical course in an individual patient. Angiogenesis has been recently reported as a potential prognostic factor in various hematological malignancies including CLL. The objective of the present study was to quantify plasma levels of key angiogenic activators vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in patients with CLL and determine their potential change after intensive fludarabine-based treatment. Peripheral blood EDTA plasma concentrations of bFGF and VEGF were measured using comercially available enzyme-linked immunosorbent assay in 73 patients with untreated CLL (43 males, 30 females, median age, 65 years, range 31-88) and 80 healthy donors serving as control group. We found statistically significant increase in concentrations in patients with chronic lymphocytic leukemia compared to the control group (p < 0.0001 for both cytokines). No differences in angiogenic factors were noted between subgroups with low vs. intermediate vs. high-risk stage according to modified Rai staging or males vs. females. In twelve patients who achieved at least partial response after intensive fludarabine-based treatment, levels of bFGF as well as VEGF decreased significantly (bFGF, p = 0.0005; VEGF, p = 0.0068); in addition, they were no more significantly different from controls (bFGF, p = 0.524; VEGF, p = 0.728). Our data showed that key angiogenic activators bFGF and VEGF were elevated in plasma ofCLL patients. Furthemore, treatment with intensive fludarabine-containing regimens resulted in significant decrease of both cytokines. These data suggest that angiogenic cytokines may indeed play a significant role in CLL biology and that treatment with combination of fludarabine, cyclophosphamide +/- rituximab may exhibit antiangiogenic properties. Further studies with longer follow-up are necessary for evaluation of a possible association between angiogenic markers and progression-free survival or overall survival.

[Achieving Bcl-2/IgH negativity in peripheral blood/bone marrow after therapy implies better prognosis for patients with follicular lymphoma]

Bcl-2/IgH rearrangement is a characteristic molecular rearrangement in patients with follicular lymphoma (FL), yet its prognostic significance is still unclear.

OBJECTIVE

Evaluation of the implications of achieving Bcl-2/IgH negativity for the prognosis of FL patients. Twenty seven patients (54%) were receiving only chemotherapy (CHT), 23 patients (46%) were receiving chemotherapy combined with monoclonal antibody anti/CD20, rituximab (R-CHT).

RESULTS

Molecular genetic remission was achieved in 7 out of 11 patients (64%) after R-CHT, and only in 2 out of 14 patients (14%) after CHT- this difference was statistically significant (p = 0.037). 4 weekly doses of rituximab were administered in a sequence to 17 out of 27 patients who had received only chemotherapy and failed to achieve complete remission. 12 out of 17 patients (71%) on this therapy were Bcl-2/IgH positive prior to treatment. 7 out of 12 (58 %) patients were no longer Bcl-2/IgH positive in a check performed after one month; the remaining 2 out of 5 patients had a negative Bcl-2/IgH record for the interval of 3 months (1 patient) or 6 (1 patient) months, respectively. The following factors were associated with the achievement of Bcl-2/IgH negativity at any point during the treatment: age < 65 years (p = 0.02) and performance status 0 + 1 according to WHO at baseline (p = 0.02). Patients who were Bcl-2/IgH negative after treatment had a lower recurrence/progression risk rate than the Bcl-2/IgH positive group of patients, i.e. 27% vs. 75% (p = 0.03), and a higher chance for progression-free survival, i.e. 81% vs. 38% (p = 0.004), event-free survival, i.e. 74% vs. 38% (p = 0.01), and overall survival, i.e. 87% vs. 74% (p = 0.05) at 2 years.

CONCLUSION

In our experience, achieving Bcl-2/IgH negativity after follicular lymphoma therapy implies a better prognosis.

[Angiogenesis in the bone marrow of patients with chronic lymphocytic leukaemia]

Angiogenesis is a process of formation of new vessels from the preexisting ones. It is involved in many physiological processes, at the same time, however, it is involved also in the progress of tumoral growth. Although a lot is known about angiogenesis in solid tumors where it plays a role in tumoral invasion and its metastatic potential, in hematological malignancies it has been appreciated only recently. However, the results of studies on abnormal angiogenesis in hematological malignancies are inconsistent. Angiogenesis can be studied at different levels; histologically, it is studied in the infiltrated tissues (lymph nodes, bone marrow) and quantified as microvessel density (MVD). The aims of our study were to introduce the method of MVD quantification in the bonemarrow using immunohistochemical detection of endothelial markers (fVIII) and then evaluate MVD in bone marrow samples in a group of patients with chronic lymphocytic leukaemia (CLL) and compare the results with a control group of patients (CON). CLL is a typical malignancy of the hematopoietic tissue but the course and the prognosis of patients with this disease vary considerably. For this reason there is urgent need for novel prognostic markers in order to assess individual patient prognosis and tailor treatment. Angiogenesis is one of the possible markers which may add more informations about the course of this disease. So far only few studies have been published about angiogenesis measured as MVD in CLL patients andthe results are inconsistent. In our study, both the number and the area of microvessels were increased in bone marrow of patients with CLL, but the number and area of sinuses were not. It can be concluded that there are signs of abnormal angiogenesis in bone marrow of patients with CLL but larger study with longer follow-up is needed to give more specific information about prognostic value of these findings.

Isotype class switching after transplantation in multiple myeloma

Switching of the paraprotein isotype or transient presence of oligoclonal bands detectable by serum immunofixation electrophoresis has been reported following not only transplantations, but also after intensive chemotherapy for leukemia. Retrospective analysis of 72 transplanted myeloma patients was carried out to determine the frequency and clinical significance of the appearance of abnormal proteins bands (APB) distinct from the original paraprotein. APB presence was observed in 31 patients (43%) already after the first autotransplant, the median interval from transplant was 2 months (range, 1 to 6 months). The most frequent occurrence of APB was observed after allogeneic transplantation. In the group of patients with APB presence more patients achieved complete remission (32.2% versus 17.1%), statistically significant differences were also established when we compared the percentage of surviving patients and overall survival, to the present date, among both groups of patients (p=0.03). All relapsed patients with previous isotype class switching had disease characterized by the same type of paraprotein as that detected at diagnosis. The development of APB is likely related to the recovery of impaired immunoglobulin production after transplantation. We confirmed favourable prognostic significance of this finding in transplanted myeloma patients.

[ZAP-70 in B-cell chronic lymphocytic leukemia: clinical significance and methods of detection]

B-cell chronic lymphocytic leukemia (B-CLL) represents a heterogeneous disease with highly variable prognosis. Clinical staging systems (Rai, Binet) fail to accurately predict the prognosis of individual patients, especially in early stages. Modern prognostic markers, mainly the mutational status of the variable regions of immunoglobulin heavy chains (IgVH) and genetic aberrations, allow more accurate risk stratification. Assessment of the expression of intracellular protein tyrosine kinase ZAP-70 represents not only a potential surrogate marker for the technically difficult and routinely unavailable assessment of the IgVH mutational status, but might also be an independent prognostic factor. Study of ZAP-70 function in B-cells has broadened our knowledge on the pathogenesis of B-CLL. Routine ZAP-70 assessment has been hindered so far mainly by the lack of harmonization and standardization of the available methods of detection.

[Angiogenesis and antiangiogenic cancer therapy]

Physiologic angiogenesis takes place during tissue growth and repair, during the female reproductive cycle, and during fetal development. Angiogenesis is also required for tumor growth and metastasis and, therefore, represents an exciting target for cancer treatment. Angiogenesis is a complex process that is tightly regulated by pro- and antiangiogenic growth factors. Pathologic angiogenesis is characterized by either excessive (eg. cancer) or inadequate (eg. coronary artery disease) neovascularization. Avascular tumors are severely restricted in their growth potential because of the lack of a blood supply. For tumors to develop in size and metastatic potential they must make an "angiogenic switch" through perturbing the local balance of proangiogenic and antiangiogenic factors. Frequently, tumors overexpress proangiogenic factors, such as vascular endothelial growth factor, allowing them to make this angiogenic switch. Two strategies used in the development of antiangiogenic agents involve the inhibition of proangiogenic factors (eg. anti-vascular endothelial growth factor monoclonal antibodies) as well as therapy with endogenous inhibitors of angiogenesis. Emerging antiangiogenic agents currently in clinical studies are discussed in this review.