Antiangiogenic and antitumor effects of bevacizumab in patients with inflammatory and locally advanced breast cancer

Bevacizumab demonstrates activity in advanced refractory fallopian tube carcinoma

The targeting of angiogenesis pathways in the treatment of gynecological cancers is an exciting development in cancer therapy. Bevacizumab has been shown to have activity in ovarian cancer through its inhibition of the vascular endothelial growth factor. Fallopian tube carcinoma is a rare malignancy and is often treated in a similar manner as ovarian carcinoma. We present a case of a complete response in a woman with refractory metastatic fallopian tube carcinoma treated with bevacizumab. This report demonstrates the significance of anti-angiogenesis therapy in the treatment of these tumors.

Oligosaccharides as anti-angiogenic agents

BACKGROUND

Several studies of drugs that inhibit tumour angiogenesis have shown improvements in the survival of cancer patients, thus validating angiogenesis as a clinically relevant target. Both intracellular and extracellular approaches have shown promising results in clinical situations.

OBJECTIVES

To compare and contrast oligosaccharide therapies and other anti-angiogenic compounds for their benefits and toxicity.

METHODS

Analysis of the relevant literature including presentations at recent conferences.

RESULTS

Receptor tyrosine kinase inhibitors are orally available but have a broad spectrum of activity which is associated with toxicity. Antibodies are associated with different toxicities, however, they are administered parenterally. Oligosaccharides that act as competitive inhibitors of heparan sulfate (HS) are in the early and late phases of clinical development. The advantage of oligosaccharides should be that they can be designed to target several angiogenic molecules, that they are relatively safe and that they can be administered subcutaneously at home. The key questions concerning their development focus on whether compounds with sufficient affinity and relative specificity can be generated, whether they are active at doses that do not perturb the coagulation cascade to a clinically dangerous level, whether the synthetic routes are scalable and, whether the current Phase III trials will yield positive results.

CONCLUSIONS

Saccharides represent a novel and exciting therapeutic approach that targets a spectrum of angiogenic molecules that cannot be inhibited through established drug development programmes.

Inflammatory breast cancer: current understanding

PURPOSE OF REVIEW

Inflammatory breast cancer is a highly aggressive variant of locally advanced breast cancer that carries a significantly worse prognosis. The purpose of this review is to highlight recent advances in the molecular modus operandi of this particular form of breast cancer.

RECENT FINDINGS

Studies on tumor cell emboli, E-cadherin, chemokine receptors, steroid hormone receptor, angiogenesis, lymphangiogenesis and gene expression all suggest significant differences with noninflammatory breast cancer and are clearly in line with a different pathogenesis of the condition.

SUMMARY

This comprehensive review will hopefully allow for better treatment modalities with targeted approaches as suggested by the early data on anti-vascular endothelial growth factor treatment in inflammatory breast cancer.

Angiogenesis as a strategic target for ovarian cancer therapy

Angiogenesis is a complex and highly regulated process that is crucial for tumor growth and metastasis. Insights into the molecular mechanisms of tumor angiogenesis have led to the identification of potential angiogenic targets and the development of novel antivascular agents. Many of these agents are being evaluated in clinical trials and have shown promising antitumor activity. This Review highlights the results of the latest clinical studies of antivascular agents in ovarian cancer and discusses the challenges and opportunities for future clinical trials.

Research Issues Affecting Preoperative Systemic Therapy for Operable Breast Cancer

Preoperative systemic therapy (PST) in operable breast cancer allows a small increase in breast conservation rates and has significant potential as a research platform. PST offers the ability to discern treatment effect in vivo, and may allow smaller trials targeting specific breast cancer subtypes and making more efficient use of resources. Early observations of a specific outcome of interest in individual patient subgroups may improve the design of larger definitive randomized adjuvant trials using survival as a main outcome. PST offers the potential for therapeutic adjustments midcourse, which assumes the existence of validated intermediate end points and effective alternative therapies. This article reviews critical research issues affecting the design of PST trials, including the appropriate selection of trial end points and markers for long-term outcome, baseline marker expression as a predictor of response, and statistical considerations using novel trial designs. Key issues regarding optimal tumor subtype selection for individual trials, novel approaches using nontherapeutic window trial designs, and ethical and advocacy considerations are also discussed. PST requires an experienced and cohesive multidisciplinary team for it to fulfill its potential in both research and clinical care.

A comparison of plasma versus histologic indices of angiogenic markers in breast cancer

BACKGROUND

Over-expression of angiogenic growth factors and their receptors, and high levels of these molecules in the blood, are a common feature of cancer although the relationships between cell expression and plasma levels are unknown. We hypothesized a significant correlation between the expression and cellular distribution of vascular endothelial growth factor (VEGF), its receptor Flt-1, and the angiopoietin receptor Tie-2 with levels of these molecules in the plasma.

METHODS

The tissue expression of VEGF, Flt-1, and Tie-2 were investigated by immunohistochemistry, and plasma levels assessed by enzyme-linked immunosorbent assay in 36 patients with breast cancer and 15 with benign breast disease.

RESULTS

Despite expected significant differences in plasma levels of the molecules (P<0.03 to <0.001), no significant differences were found in Tie-2, VEGF, and Flt-1 tissue expression between breast cancer and benign disease controls. No significant correlations were observed between plasma levels of their tissue expression.

CONCLUSIONS

Tissue expression of Tie-2, VEGF, and Flt-1 may not be an overly sensitive tool for assessing abnormalities of coagulation, platelet activation, and angiogenesis in human cancer. Plasma markers may not be representative of tumor activity, and may not come wholly from tumor cells. Instead these markers may be indicative of endothelial dysfunction in cancer patients.

The effect of bevacizumab (Avastin) on neuroimaging of brain metastases

BACKGROUND

Bevacizumab is FDA approved to treat colon cancer and is currently used off label for metastatic breast, kidney, and lung cancers. Bevacizumab is a monoclonal antibody that binds to, and inactivates, VEGF and is believed to be antiangiogenic.

CASE DESCRIPTION

The authors report the case of a 54-year-old woman with metastatic infiltrating ductal breast carcinoma who developed left occipital and right parietal intraaxial contrast-enhancing masses on surveillance magnetic resonance imaging (MRI). After surgical resection, she was placed on bevacizumab for control of systemic disease. Six months later, a nonenhancing right occipital lesion was detected on MRI. After stopping bevacizumab therapy, the patient underwent microsurgical resection of the lesion. Histopathologic examination was consistent with metastatic breast cancer indistinguishable from her previously resected enhancing brain metastasis. Six weeks after stopping bevacizumab therapy and 3 weeks after microsurgical resection, a new contrast-enhancing mass was noted on magnetic resonance in the right temporal lobe.

CONCLUSION

This case is unique in that we have neuroimaging on prebevacizumab, concurrent bevacizumab, and postbevacizumab brain metastases in the same patient with a single cancer primary, thus, assuring that alterations in neuroimaging characteristics are consistent with bevacizumab effect. As an internal control, it provides strong support for the premise that bevacizumab therapy can confound the diagnosis of brain metastases because of its effect on tumor enhancement.

Adjuvant biologic therapy for breast cancer

Breast cancer continues to be a major health problem despite a decrease in mortality rates over the past 2 decades. Although many advances have been made in the treatment of breast cancer, drug therapy for the disease continues to evolve as more is learned about cell biology and cellular signaling pathways. The development of targeted agents offers the hope of new therapies with better efficacy and tolerability. Biologic therapy has been a cornerstone of targeted therapy for the treatment of advanced breast cancer and is now entering the adjuvant arena. This review summarizes the results of several adjuvant studies and discusses future directions for breast cancer biotherapy.

VEGF signaling inhibitors: more pro-apoptotic than anti-angiogenic

The vascular endothelial growth factor (VEGF) family of polypeptide growth factors regulates a family of VEGF receptor (VEGFR) tyrosine kinases with pleiotropic downstream effects. Angiogenesis is the best known of these effects, but additional VEGF-dependent actions include increased vascular permeability, paracrine/autocrine growth factor release, enhancement of cell motility, and inhibition of apoptosis. In theory, therapeutic inhibition of angiogenesis should reduce tumor perfusion and thus increase tumor hypoxia and chemoresistance, but in clinical practice the VEGF antibody bevacizumab acts as a broad-spectrum chemosensitizer. Since VEGFR expression occurs in many tumor types, such chemosensitization is more readily explained by direct inhibition of tumor cell survival signals than by indirect stromal/vascular effects. The emerging model of anti-VEGF drug action being mediated primarily by tumoral (as distinct from endothelial) VEGFRs has clinically important implications for optimizing the anti-metastatic efficacy of this expanding drug class.

Phase I evaluation of CDP791, a PEGylated di-Fab' conjugate that binds vascular endothelial growth factor receptor 2

PURPOSE

Specific blocking of vascular endothelial growth factor receptor 2 (VEGFR-2) is a novel therapeutic approach. Here, we report the first phase I clinical trial evaluation of CDP791, a PEGylated di-Fab' conjugate that binds VEGFR-2.

EXPERIMENTAL DESIGN

Cohorts of patients received CDP791 at doses between 0.3 and 30 mg/kg every 3 weeks for the initial two doses.

RESULTS

The compound was well tolerated with no dose-limiting toxicity. Dose-related hypertension was observed in patients receiving CDP791 10 mg/kg or more and several patients on the higher doses developed infusion-related cutaneous hemangiomata arising 28 to 106 days after the first drug administration and resolving 3 weeks after cessation. Biopsy and histologic evaluation showed that CDP791-bound VEGFR-2 is non-phosphorylated, suggesting that the drug is biologically active. Concentrations of CDP791 considered biologically relevant were sustained for 3 weeks when doses of 10 mg/kg or more were administered. Although no reductions in vascular permeability were recorded using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), there was a significant dose level-related reduction in tumor growth. While challenging the recent dogma that active VEGF inhibitors should modulate DCE-MRI measurements of vascular permeability, this highlights the potential of serial three-dimensional tumor measurements to detect tumor growth arrest. Twelve patients received drug for more than two treatments, although no partial or complete responses were seen.

CONCLUSION

The data show that CDP791 is biologically active and well tolerated, achieving appropriate plasma concentrations when administered at 10 mg/kg or more every 3 weeks.

Bevacizumab: in first-line treatment of metastatic breast cancer

Bevacizumab, a recombinant humanised monoclonal antibody against vascular endothelial growth factor, is approved in Europe as first-line therapy for metastatic breast cancer (mBC) and metastatic carcinoma of the colon or rectum (mCRC); the European Medicines Agency gave a positive opinion recommending its use in non-small-cell lung cancer (NSCLC) and is also considering other indications. In the US, it is licensed for use for mCRC and NSCLC, with its use as first-line treatment in mBC under review by the US FDA. In the pivotal E2100 trial in >700 previously untreated patients with locally recurrent or mBC, recipients of bevacizumab plus paclitaxel had a statistically and clinically significant increase in progression-free survival versus paclitaxel recipients (13.3 vs 6.7 months; hazard ratio 0.48; p < 0.001) [primary endpoint]. There was also a >2-fold higher objective response rate in the bevacizumab plus paclitaxel arm than in the paclitaxel arm; the between-group difference in median overall survival did not reach statistical significance (25.7 vs 23.8 months). Bevacizumab had an acceptable tolerability profile in these patients, with the majority of adverse events being generally mild to moderate in severity. There are targeted adverse events, including gastrointestinal perforations, wound healing complications and haemorrhage, which although they occur infrequently (incidence <=2%), are potentially life-threatening and may cause morbidity.

Antiangiogenic and antitumor effects of SRC inhibition in ovarian carcinoma

Src, a nonreceptor tyrosine kinase, is a key mediator for multiple signaling pathways that regulate critical cellular functions and is often aberrantly activated in a number of solid tumors, including ovarian carcinoma. The purpose of this study was to determine the role of activated Src inhibition on tumor growth in an orthotopic murine model of ovarian carcinoma. In vitro studies on HeyA8 and SKOV3ip1 cell lines revealed that Src inhibition by the Src-selective inhibitor, AP23846, occurred within 1 hour and responded in a dose-dependent manner. Furthermore, Src inhibition enhanced the cytotoxicity of docetaxel in both chemosensitive and chemoresistant ovarian cancer cell lines, HeyA8 and HeyA8-MDR, respectively. In vivo, Src inhibition by AP23994, an orally bioavailable analogue of AP23846, significantly decreased tumor burden in HeyA8 (P = 0.02), SKOV3ip1 (P = 0.01), as well as HeyA8-MDR (P < 0.03) relative to the untreated controls. However, the greatest effect on tumor reduction was observed in combination therapy with docetaxel (P < 0.001, P = 0.002, and P = 0.01, for the above models, respectively). Proliferating cell nuclear antigen staining showed that Src inhibition alone (P = 0.02) and in combination with docetaxel (P = 0.007) significantly reduced tumor proliferation. In addition, Src inhibition alone and in combination with docetaxel significantly down-regulated tumoral production of vascular endothelial growth factor and interleukin 8, whereas combination therapy decreased the microvessel density (P = 0.02) and significantly affected vascular permeability (P < 0.05). In summary, Src inhibition with AP23994 has potent antiangiogenic effects and significantly reduces tumor burden in preclinical ovarian cancer models. Thus, Src inhibition may be an attractive therapeutic approach for patients with ovarian carcinoma.

Bevacizumab plus irinotecan in recurrent glioblastoma multiforme

PURPOSE

The prognosis for patients with recurrent glioblastoma multiforme is poor, with a median survival of 3 to 6 months. We performed a phase II trial of bevacizumab, a monoclonal antibody to vascular endothelial growth factor, in combination with irinotecan.

PATIENTS AND METHODS

This phase II trial included two cohorts of patients. The initial cohort, comprising 23 patients, received bevacizumab at 10 mg/kg plus irinotecan every 2 weeks. The dose of irinotecan was based on the patient's anticonvulsant: Patients taking enzyme-inducing antiepileptic drugs (EIAEDs) received 340 mg/m2, and patients not taking EIAEDs received 125 mg/m2. After this regimen was deemed safe and effective, the irinotecan schedule was changed to an accepted brain tumor regimen of four doses in 6 weeks, in anticipation of a phase III randomized trial of irinotecan versus irinotecan and bevacizumab. The second cohort, comprising 12 patients, received bevacizumab 15 mg/kg every 21 days and irinotecan on days 1, 8, 22, and 29. Each cycle was 6 weeks long and concluded with patient evaluations, including magnetic resonance imaging.

RESULTS

The 6-month progression-free survival among all 35 patients was 46% (95% CI, 32% to 66%). The 6-month overall survival was 77% (95% CI, 64% to 92%). Twenty of the 35 patients (57%; 95% CI, 39% to 74%) had at least a partial response. One patient developed a CNS hemorrhage, which occurred in his 10th cycle. Four patients developed thromboembolic complications (deep venous thrombosis and/or pulmonary emboli).

CONCLUSION

Bevacizumab and irinotecan is an effective treatment for recurrent glioblastoma multiforme and has moderate toxicity.

MRI of tumor angiogenesis

Angiogenesis has long been established as a key element in the pathophysiology of tumor growth and metastasis. Increasingly, new molecularly targeted antiangiogenic drugs are being developed in the fight against cancer. These drugs bring with them a need for an accurate means of diagnosing tumor angiogenesis and monitoring response to treatment. Imaging techniques can offer this in a noninvasive way, while also providing functional information about the tumor. Among the many clinical imaging techniques available, MRI alone can provide relatively good spatial resolution and specificity, without ionizing radiation and with limited side effects. Arterial spin labeling (ASL) and blood oxygenation level-dependent (BOLD) imaging techniques can be employed to confer indirect measures of angiogenesis, such as blood flow and blood volume, without the need for external contrast agents. Dynamic contrast-enhanced (DCE)-MRI is rapidly emerging as a standard method for directly measuring angiogenesis during angiogenesis-inhibitor drug trials. As macromolecular MR contrast agents become available, they will inevitably be utilized in the assessment of tumor perfusion and vessel permeability. Meanwhile, technological advances have made imaging at a molecular level a possibility. They have brought the potential to directly target MR contrast agents to markers of angiogenesis, such as the alpha(v)beta(3) integrin. Before this is used clinically, however, substantial gains in sensitivity brought about by improved coils, pulse sequences, and contrast agents will be needed. Herein we discuss the techniques currently available for MRI of angiogenesis, along with their respective advantages and disadvantages, and what the future holds for this evolving field of imaging.

Validation of dynamic contrast-enhanced magnetic resonance imaging-derived vascular permeability measurements using quantitative autoradiography in the RG2 rat brain tumor model

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely used to evaluate tumor permeability, yet measurements have not been directly validated in brain tumors. Our purpose was to compare estimates of forward leakage K(trans) derived from DCE-MRI to the estimates K obtained using [(14)C]aminoisobutyric acid quantitative autoradiography ([(14)C]AIB QAR), an established method of evaluating blood-tumor barrier permeability. Both DCE-MRI and [(14)C]AIB QAR were performed in five rats 9 to 11 days following tumor implantation. K(trans) in the tumor was estimated from DCE-MRI using the threeparameter general kinetic model and a measured vascular input function. K(i) was estimated from QAR data using regions of interest (ROI) closely corresponding to those used to estimate K(trans). K(trans) and K(i) correlated with each other for two independent sets of central tumor ROI (R = 0.905, P = .035; R = 0.933, P = .021). In an additional six rats, K(trans) was estimated on two occasions to show reproducibility (intraclass coefficient = 0.9993; coefficient of variance = 6.07%). In vivo blood-tumor permeability parameters derived from DCE-MRI are reproducible and correlate with the gold standard for quantifying blood tumor barrier permeability, [(14)C]AIB QAR.

Inflammatory Breast Cancer as a Model Disease to Study Tumor Angiogenesis: Results of a Phase IB Trial of Combination SU5416 and Doxorubicin

PURPOSE

We used inflammatory breast cancer (IBC) as a model disease to investigate biological changes associated with an antiangiogenesis agent, SU5416, combined with doxorubicin.

EXPERIMENTAL DESIGN

Patients with stage IIIB or IV IBC were treated neoadjuvantly with the combination of SU5416 and doxorubicin for induction therapy. The dose of SU5416 (administered on days 1 and 4, every 3 weeks) and doxorubicin (administered on day 1 every 3 weeks) were escalated in cohorts of three patients starting at 110 and 60 mg/m2, respectively, for a total of five cycles leading up to mastectomy. Patients underwent serial assessment (pharmacokinetic sampling, biopsy of breast, tumor blood flow dynamic contrast-enhanced magnetic resonance imaging, plasma angiogenesis, and endothelial cell damage markers) prior to treatment, at the end of cycles no. 2 and no. 5, and after mastectomy.

RESULTS

Eighteen patients were enrolled; neutropenia was dose-limiting, and overall median survival was not reached (50 months of study follow-up). Four patients (22%) experienced congestive heart failure, which resolved and were likely attributable to a smaller volume of distribution and higher Cmax of doxorubicin in combination with SU5416. We did observe a significant decline in tumor blood flow using Kep calculated by Brix (pretreatment versus post-cycle no. 5; P = 0.033), trend for a decline in tumor microvessel density after treatment, and low baseline levels of soluble intracellular adhesion molecule were associated with improved event-free survival.

CONCLUSIONS

This study showed evidence of an unfavorable cardiac interaction between SU5416 and doxorubicin, which prohibits further investigation of this combination. However, this study supports the importance of using IBC as a model for investigating angiogenesis inhibitors.

Antiangiogenics: the potential role of integrating this novel treatment modality with chemoradiation for solid cancers

Although still in very early stages of clinical development, the combination of antiangiogenics with contemporary chemoradiotherapy regimens has emerged as a feasible and promising approach to many cancers. We review the rationale and the current understanding of antiangiogenics and their therapeutic potential in combination with chemoradiotherapy. Finally, we offer a perspective on future research directions aimed at making this complex therapeutic approach successful in the clinic.

Inflammatory Breast Cancer: Dynamic Contrast-enhanced MR in Patients Receiving Bevacizumab—Initial Experience

PURPOSE

To retrospectively compare three dynamic contrast material-enhanced magnetic resonance (MR) imaging (dynamic MR imaging) analytic methods to determine the parameter or combination of parameters most strongly associated with changes in tumor microvasculature during treatment with bevacizumab alone and bevacizumab plus chemotherapy in patients with inflammatory or locally advanced breast cancer.

MATERIALS AND METHODS

This study was conducted in accordance with the institutional review board of the National Cancer Institute and was compliant with the Privacy Act of 1974. Informed consent was obtained from all patients. Patients with inflammatory or locally advanced breast cancer were treated with one cycle of bevacizumab alone (cycle 1) followed by six cycles of combination bevacizumab and chemotherapy (cycles 2-7). Serial dynamic MR images were obtained, and the kinetic parameters measured by using three dynamic analytic MR methods (heuristic, Brix, and general kinetic models) and two region-of-interest strategies were compared by using two-sided statistical tests. A P value of .01 was required for significance.

RESULTS

In 19 patients, with use of a whole-tumor region of interest, the authors observed a significant decrease in the median values of three parameters measured from baseline to cycle 1: forward transfer rate constant (Ktrans) (-34% relative change, P=.003), backflow compartmental rate constant extravascular and extracellular to plasma (Kep) (-15% relative change, P<.001), and integrated area under the gadolinium concentration curve (IAUGC) at 180 seconds (-23% relative change, P=.009). A trend toward differences in the heuristic slope of the washout curve between responders and nonresponders to therapy was observed after cycle 1 (bevacizumab alone, P=.02). The median relative change in slope of the wash-in curve from baseline to cycle 4 was significantly different between responders and nonresponders (P=.009).

CONCLUSION

The dynamic contrast-enhanced MR parameters Ktrans, Kep, and IAUGC at 180 seconds appear to have the strongest association with early physiologic response to bevacizumab. Clinical trial registration no. NCT00016549

Mechanisms of disease: angiogenesis and the management of breast cancer

Demonstration of the clinically significant activity of bevacizumab in breast cancer has attracted a great deal of interest. Numerous other antiangiogenic treatments are in clinical development and some established therapies including tamoxifen and trastuzumab might function, in part, by suppressing angiogenesis. In this Review, we discuss the potential of various components of the angiogenic pathway as prognostic and predictive factors in breast cancer. In addition, we describe existing clinical trials of antiangiogenic agents and the challenges facing the clinical development and optimum use of these agents for the treatment of breast cancer.

Oral vinorelbine: role in the management of metastatic breast cancer

The treatment of advanced breast cancer is continually evolving, with the aim of improving the quality and duration of remission and, in some instances, survival. In this setting, the importance of quality of life cannot be underestimated, and growing attention is being paid to treatment convenience and compliance. New anticancer agents have improved efficacy, but for many of them, toxicity often remains a problem. Vinorelbine seems to represent both an active and a well tolerated treatment for metastatic breast cancer. In particular, the oral formulation has similar efficacy to that of the injectable formulation and has demonstrated generally favourable tolerability, with a high degree of acceptance by both patients and physicians. The availability of this and other novel, well tolerated and effective treatments provides greater potential to tailor treatment to meet individual patient needs and, therefore, also provide the potential to improve patient outcomes. Preliminary data suggest that oral vinorelbine may permit continued, effective chemotherapy when further parenteral therapy with more intensive and more toxic agents is considered inappropriate. Early findings also suggest that oral vinorelbine, when administered together with another new oral agent, capecitabine, may be a valid choice in metastatic breast cancer treatment. Furthermore, vinorelbine plus the monoclonal antibody trastuzumab, with or without oral capecitabine, appears to be another regimen that may be worthy of additional study in patients with human epidermal growth factor-2 positive advanced breast cancer.

Emerging treatments and gene expression profiling in high-risk medulloblastoma

The past decades have seen an increase in the survival rates of patients with standard-risk medulloblastoma. Efforts have, therefore, been focused on obtaining better results in the treatment of patients with high-risk tumors. In addition to consolidated therapies, novel approaches such as small molecules, monoclonal antibodies, and antiangiogenic therapies that aim to improve outcomes and quality of life are now available through new breakthroughs in the molecular biology of medulloblastoma. The advent of innovative anticancer drugs tested in brain tumors has important consequences for personalized therapy. Gene expression profiling of medulloblastoma can be used to identify the genes and signaling transduction pathways that are crucial for the tumorigenesis process, thereby revealing both new targets for therapy and sensitive/resistance phenotypes. The interpretation of microarray data for new treatments of patients with high-risk medulloblastoma, as well as other poor prognosis tumors, should be developed through a consensus multidisciplinary approach involving oncologists, neurosurgeons, radiotherapists, biotechnologists, bioinformaticists, and other professionals.

Imaging tumor vascular heterogeneity and angiogenesis using dynamic contrast-enhanced magnetic resonance imaging

This article reviews the application of dynamic contrast-enhanced magnetic resonance imaging in both clinical studies and early-phase trials of angiogenesis inhibitors. Emphasis is placed on how variation in image acquisition and analysis affects the meaning and use of derived variables. We then review the potential for future developments, with particular reference to the application of dynamic contrast-enhanced magnetic resonance imaging to evaluate the heterogeneity of tumor tissues.

VEGF-targeted cancer therapy strategies: current progress, hurdles and future prospects

Despite setbacks, the clinical development of antiangiogenic agents has accelerated remarkably over the past 3-4 years. Consequently, there are currently three direct inhibitors of the VEGF pathway approved for use in cancer therapy. Other agents that block the VEGF pathway are in advanced stages of clinical development and have shown promising results. With these exciting developments come crucial questions regarding the use of these new molecular-targeted agents, alone or in combination with standard cytotoxic or targeted agents. Importantly, the mechanisms of action of anti-VEGF therapy remain unknown. Here, we discuss several potential mechanisms of action such as tumor vascular normalization, bone marrow-derived cell recruitment blockade and cytostatic effects of anti-VEGF therapy. We review the current progress, the major stumbling blocks and the future directions for anti-cancer therapy using anti-VEGF agents, emphasizing clarification of the underlying molecular mechanisms of action and biomarker identification and validation.

Selective targeting and potent control of tumor growth using an EphA2/CD3-Bispecific single-chain antibody construct

The EphA2 receptor tyrosine kinase is frequently overexpressed and functionally altered in malignant cells and thus provides opportunities for selective targeting of tumor cells. We describe here the development of a novel, bispecific single-chain antibody (bscAb) referred to as bscEphA2xCD3. This molecule simultaneously targets EphA2 on tumor cells and the T-cell receptor/CD3 complex on T cells and possesses structural and functional characteristics of the recently developed BiTE technology. An EphA2-specific single-chain antibody was selected for recognition of an epitope that is preferentially exposed on malignant cells based on the concept of epitope exclusion; this was fused to a CD3-specific single-chain antibody to generate bscEphA2xCD3. The resultant bscAb redirected unstimulated human T cells to lyse EphA2-expressing tumor cells both in vitro and in vivo. In separate experiments, efficient tumor cell lysis was achieved in vitro at drug concentrations <or=1 microg/mL, at a low T-cell effector-to-tumor target cell ratio (1:1), and with tumor cells that possess few available binding sites (2,400 per cell) for bscEphA2xCD3. Time-lapsed microscopy revealed potent cytotoxic activity of bscEphA2xCD3-activated T cells against monolayers of malignant cells but not against monolayers of nontransformed EphA2-positive cells except at the edges of the monolayer where the target epitope was exposed. BscEphA2xCD3 was also efficacious in human xenograft mouse models modified to show human T-cell killing of tumors. Together, our results reveal opportunities for redirecting the potent activity of cytotoxic T cells towards tumor cells that express selectively accessible epitopes and establish EphA2-specific bscAb molecules as novel and potent therapeutics with selectivity for tumor cells.

Dynamic Contrast Enhanced Magnetic Resonance Imaging in Oncology: Theory, Data Acquisition, Analysis, and Examples

Dynamic contrast enhanced MRI (DCE-MRI) enables the quantitative assessment of tumor status and has found application in both pre-clinical tumor models as well as clinical oncology. DCE-MRI requires the serial acquisition of images before and after the injection of a paramagnetic contrast agent so that the variation of MR signal intensity with time can be recorded for each image voxel. As the agent enters into a tissue, it changes the MR signal intensity from the tissue to a degree that depends on the local concentration. After the agent is transported out of the tissue, the MR signal intensity returns to its' baseline value. By analyzing the associated signal intensity time course using an appropriate mathematical model, physiological parameters related to blood flow, vessel permeability, and tissue volume fractions can be extracted for each voxel or region of interest.In this review we first discuss the basic physics of this methodology, and then present technical aspects of how DCE-MRI data are acquired and analyzed. We also discuss appropriate models of contrast agent kinetics and how these can be used to elucidate tissue characteristics of importance in cancer biology. We conclude by briefly summarizing some future goals and demands of DCE-MRI.

New agents in development for breast cancer

PURPOSE OF REVIEW

This review summarizes the continuing value of some therapeutic drugs and new agents under development for the treatment of breast cancer.

RECENT FINDINGS

Overexpression and activation of various growth factor receptors occurs frequently in human breast cancer. Therapeutic approaches mainly involve the epidermal growth factor receptor family, insulin-like growth factor receptor and vascular endothelial growth factor receptor. Therapeutic agents targeting these receptors include the monoclonal antibodies trastuzumab and pertuzumab, and the small-molecule inhibitors gefitinib and erlotinib. Other small-molecule and dual inhibitors are in development, some of which have been demonstrated to have higher efficacy in the treatment of breast cancer. The selective estrogen receptor modulators and aromatase inhibitors continue to be valuable in the endocrine therapy of breast cancer. These drugs have been shown to have higher efficacy than conventional therapy agents, and to have extensive potential, especially in the treatment of postmenopausal women with advanced breast cancer.

SUMMARY

Approved agents including epidermal growth factor receptor-targeted inhibitor, selective estrogen receptor modulators and aromatase inhibitors continue to be valuable in treating breast cancer. To overcome the acquired resistance caused by these agents and to enhance the therapy effect, the development of new and specific dual inhibitors targeting various growth factor receptors will be important in the future.

Vascular endothelial growth factor and bevacitumab in breast cancer

Cancer development requires neovascularization. The level of angiogenic activity in breast cancer has been shown to be a determinant of disease progression and survival. Vascular endothelial growth factor (VEGF) is a one of the most essential pro-angiogenic growth factors expressed by most cancer-cell types and certain tumor stromal cells. Blocking the action of VEGF appears to be a promising anti-angiogenic approach to treat multiple types of solid tumors including breast cancer, and clinical trials using agents which target VEGF were launched beginning in the late 1990s. The effort reached fruition in 2005 with the first report of a large, prospective randomized trial of anti-VEGF therapy in patients with metastatic breast cancer (MBC), which demonstrated the benefit of adding the monoclonal antibody bevacizumab to the chemotherapeutic agent paclitaxel. The success of this trial provided proof of principle that inhibition of angiogenesis has the potential to enhance the effectiveness of treatment of this disease. Adjuvant therapy trials are in development with bevacizumab and numerous other anti-VEGF agents are now being tested in patients with breast cancer in various settings. Nevertheless, since bevacizumab monotherapy has minimal activity, a question for future therapeutic development of these agents in breast cancer relates to the interaction between anti-angiogenic strategies and cytotoxic therapies. Further research is still needed for complete understanding of the exact role of VEGF and angiogenesis in health and disease, to take best advantage and avoid the adverse effects of anti-angiogenic therapy.

Primary systemic therapy for operable breast cancer: A review of clinical trials and perspectives

Primary systemic therapy represents the standard of care for locally advanced breast cancer and has becoming an attractive alternative in earlier stages. A part from the proven advantage of increasing the rate of breast conservative surgery, the up front use of systemic therapy can allow for an in vivo test of treatment sensitivity, and response to primary treatment discriminates patients at different prognosis. This review will summarize the more relevant data on the preoperative treatment with chemotherapy, hormonal therapy and targeted agents.

Promise and Progress for Functional and Molecular Imaging of Response to Targeted Therapies

Biomarkers to predict or monitor therapy response are becoming essential components of drug developer's armamentaria. Molecular and functional imaging has particular promise as a biomarker for anticancer therapies because it is non-invasive, can be used longitudinally and provides information on the whole patient or tumor. Despite this promise, molecular or functional imaging endpoints are not routinely incorporated into clinical trial design. As the costs of clinical trials and drug development become prohibitively more expensive, the need for improved biomarkers has become imperative and thus, the relatively high cost of imaging is justified. Imaging endpoints, such as Diffusion-Weighted MRI, DCE-MRI and FDG-PET have the potential to make drug development more efficient at all phases, from discovery screening with in vivo pharmacodynamics in animal models through the phase III enrichment of the patient population for potential responders. This review focuses on the progress of imaging responses to new classes of anti-cancer therapies targeted against PI3 kinase/AKT, HIF-1alpha and VEGF. The ultimate promise of molecular and functional imaging is to theragnostically predict response prior to commencement of targeted therapy.

Docetaxel/anthracycline combinations for breast cancer treatment

Anthracyclines and taxanes represent the most active group of cytotoxic agents for the treatment of breast cancer. Combining docetaxel with anthracyclines is widely used in the clinic, but, due to an overlap in toxicities this strategy remains somewhat challenging. Combinations of docetaxel with doxorubicin, epirubicin or liposomal doxorubicin in conventional or dose-dense cycles are reviewed in this article. A specific focus is given to the three-drug combination of docetaxel, doxorubicin and cyclophosphamide (TAC regimen), as it is registered for the adjuvant treatment of node-positive breast cancer. Febrile neutropenia and associated toxicities are frequently associated with the TAC combination. However, when used as primary prophylaxis with granulocyte growth factors, as well as antibiotics, this regimen is considered as a safely-applicable standard option for early breast cancer treatment.

Challenges for patient selection with VEGF inhibitors

As targeted therapies for cancer become increasingly integrated into standard practice, appropriate selection of the patients most likely to benefit from these therapies is now receiving critical scrutiny. Early experience with therapies directed at targets that are definitively overactive (e.g. the bcr-abl tyrosine kinase targeted by imatinib) or over-expressed [e.g. the human epidermal growth factor receptor 2 (HER2) targeted by trastuzumab] has generated the perception that pre-treatment target assessment is a pre-requisite for therapy with all targeted agents. However, emerging evidence suggests that this is not presently feasible for anti-angiogenic agents. Despite considerable evidence for the association of intratumoral and/or plasma vascular endothelial growth factor (VEGF) levels with tumor progression and/or poor prognosis, pre-treatment VEGF levels do not appear to be predictive of response to anti-angiogenic therapy. This may possibly be due to the complexity of the angiogenic pathways and the limitations associated with current methods of VEGF detection and quantification; e.g. low assay sensitivity and lack of standardized methods could prevent detection of very small increases in VEGF, which may be clinically important in patients with tumors that are highly dependent on this growth factor. In addition to a general lack of agreement as to the relative clinical relevance of circulating versus tumor VEGF levels, the absence of a 'gold standard' VEGF detection assay and the lack of a predefined, clinically relevant cut-off pose a significant hindrance to the clinical utility of VEGF measurements for therapy selection. Given the fundamental importance of angiogenesis for tumor growth and progression, and the key role of VEGF in these processes, presently it seems appropriate to view anti-VEGF agents such as bevacizumab (Avastin) as having potential utility, independently of pre-treatment screening. Further research is needed to define the relationship between potential surrogate markers of VEGF pathway activity and clinical outcomes.

Drug insight: VEGF as a therapeutic target for breast cancer

Angiogenesis is implicated in the pathogenesis of malignancy and metastasis. Inhibition of angiogenesis has demonstrated clinically significant improvements in outcomes in a variety of malignancies, including breast cancer. The humanized monoclonal antibody against VEGF, bevacizumab, is the clinically most mature of the antiangiogenic agents and has recently been shown to improve outcome when combined with chemotherapy in the first-line metastatic setting of breast cancer. A variety of other antiangiogenic agents are currently under investigation, including drugs that inhibit the VEGF receptor 2, the cognate receptor for VEGF found on endothelial cells. The combination of antiangiogenic drugs with one another and with other biologic agents is also being explored in an attempt to improve efficacy and to overcome the drug resistance seen with the initial studies of antiangiogenic agents. This Review will focus on the current state of therapeutics designed to inhibit this angiogenic process in breast cancer.

Mechanisms of action of bevacizumab as a component of therapy for metastatic colorectal cancer

Tumor angiogenesis is a complex process that requires the coordinated activities of various effector molecules and cell types. While tumor vasculature can nourish the tumor, it is structurally and functionally abnormal, leading to elevated interstitial pressure and non-uniform tumor perfusion. The resultant hypoxia leads to the selection of more aggressive tumor cells, owing in part to an increase in the levels of the transcription factor hypoxia-inducible factor-1, which in turn leads to an increase in the expression of vascular endothelial growth factor (VEGF). The expression of VEGF is upregulated in many tumors, and the levels of this factor correlate not only with the extent of tumor angiogenesis but also with clinical prognosis. VEGF-targeted therapies, such as bevacizumab, exert their effects through a number of potential mechanisms, including (1) inhibition of new vessel growth, (2) regression of newly formed tumor vasculature, (3) alteration of vascular function and tumor blood flow ("normalization"), and (4) direct effects on tumor cells. Because of the presumed cytostatic mechanism of action of antiangiogenic agents, the efficacy of bevacizumab is most appropriately assessed through survival end points rather than the objective-response end points that have traditionally been used with cytotoxic agents. However, bevacizumab has been shown to increase the response rates with chemotherapy in almost all tumor types studied in phase III trials.

Contrast-enhanced magnetic resonance imaging of central nervous system tumors: agents, mechanisms, and applications

Brain tumors are one of the most common neoplasms in young adults and are associated with a high mortality and disability rate. Magnetic resonance imaging (MRI) is widely accepted to be the most sensitive imaging modality in the assessment of cerebral neoplasms. Because the detection, characterization, and exact delineation of brain tumors require a high lesion contrast that depends on the signal of the lesion in relation to the surrounding tissue, contrast media is given routinely. Anatomical and functional, contrast agent-based MRI techniques allow for a better differential diagnosis, grading, and especially therapy decision, planing, and follow-up. In this article, the basics of contrast enhancement of brain tumors will be reviewed. The underlying pathology of a disrupted blood-brain barrier and drug influences will be discussed. An overview of the currently available contrast media and the influences of dosage, field strength, and application on the tumor tissue contrast will be given. Challenging, contrast-enhanced, functional imaging techniques, such as perfusion MRI and dynamic contrast-enhanced MRI, are presented both from the technical side and the clinical experience in the assessment of brain tumors. The advantages over conventional, anatomical MRI techniques will be discussed as well as possible pitfalls and drawbacks.

Chemotherapy and Antiangiogenic Agents in Non-Small-Cell Lung Cancer

Angiogenesis, the growth of new vessels from preexisting vessels, is a fundamental step in tumor growth and progression. Tumor-related angiogenesis has become an attractive target for anticancer therapy. Vascular endothelial growth factor (VEGF) is a key angiogenic factor implicated in tumor blood vessel formation and permeability. Overexpression of VEGF has been observed in a variety of cancers and has been associated with a worse relapse-free and overall survival. A large randomized trial recently demonstrated an improvement in overall survival when bevacizumab, a humanized monoclonal antibody against VEGF, was combined with chemotherapy in patients with advanced non-small-cell lung cancer. Small molecule inhibitors targeting the VEGF receptor and the tyrosine kinase receptor have also shown promise when combined with standard chemotherapeutic agents in patients with advanced non-small-cell lung cancer. There is emerging evidence that inhibition of a single target leads to upregulation of other angiogenic signaling cascades. Future directions will include the use of these agents in combination with one another as well as in combination with chemotherapy and radiation therapy in patients with early-stage (IA-IIIB) disease.

DCE-MRI biomarkers in the clinical evaluation of antiangiogenic and vascular disrupting agents

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is now frequently used in early clinical trial assessment of antiangiogenic and vascular disrupting compounds. Evidence of drug efficacy and dose-dependent response has been demonstrated with some angiogenesis inhibitors. This review highlights the critical issues that influence T(1)-weighted DCE-MRI data acquisition and analysis, identifies important areas for future development and reviews the clinical trial findings to date.

Rapid vascular regrowth in tumors after reversal of VEGF inhibition

Inhibitors of VEGF signaling can block angiogenesis and reduce tumor vascularity, but little is known about the reversibility of these changes after treatment ends. In the present study, regrowth of blood vessels in spontaneous RIP-Tag2 tumors and implanted Lewis lung carcinomas in mice was assessed after inhibition of VEGF receptor signaling by AG-013736 or AG-028262 for 7 days. Both agents caused loss of 50%-60% of tumor vasculature. Empty sleeves of basement membrane were left behind. Pericytes also survived but had less alpha-SMA immunoreactivity. One day after drug withdrawal, endothelial sprouts grew into empty sleeves of basement membrane. Vessel patency and connection to the bloodstream followed close behind. By 7 days, tumors were fully revascularized, and the pericyte phenotype returned to baseline. Importantly, the regrown vasculature regressed as much during a second treatment as it did in the first. Inhibition of MMPs or targeting of type IV collagen cryptic sites by antibody HUIV26 did not eliminate the sleeves or slow revascularization. These results suggest that empty sleeves of basement membrane and accompanying pericytes provide a scaffold for rapid revascularization of tumors after removal of anti-VEGF therapy and highlight their importance as potential targets in cancer therapy.

Angiogenesis as targeted breast cancer therapy

Neo-angiogenesis appears to be a critical feature of tumor growth, migration, and metastasis. Therefore, inhibition of angiogenesis is an appealing strategy for treatment of cancer. Since angiogenesis is the result of several mechanistic processes, controlled by numerable pro- and anti-angiogenic factors and their receptors, multiple possibilities to prevent or reverse tumor-induced neo-vascularization have been proposed. Of these, currently, the most promising approach has been the use of bevacizumab, a humanized monoclonal antibody directed against the most potent pro-angiogenic factor, vascular endothelial growth factor (VEGF). Bevacizumab has been shown to be active in several malignancies, in particular colo-rectal cancer. Although early studies of bevacizumab in far-advanced metastatic breast cancer were disappointing, the results of a recently reported clinical trial by the Eastern Oncology Group comparing first line paclitaxel with or without bevacizumab has demonstrated statistically significant improvements in response rates and time progression. Ongoing studies are now investigating the benefits of bevacizumab with other chemotherapeutic and biologic agents in early metastatic disease as well as in the adjuvant setting. Other anti-angiogenic agents remain in early clinical trials. Small molecular inhibitors of VEGF receptor tyrosine kinase activity, such as sunitinib, appear promising. Nearly 40 years after it was first proposed, inhibition of angiogenesis appears to be gaining a role in medical oncology.

Integration of quantitative DCE-MRI and ADC mapping to monitor treatment response in human breast cancer: initial results

PURPOSE

The objective of this study was to assess changes in the water apparent diffusion coefficient (ADC) and in pharmacokinetic parameters obtained from the fast-exchange regime (FXR) modeling of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) during neoadjuvant chemotherapy in breast cancer.

MATERIALS AND METHODS

Eleven patients with locally advanced breast cancer underwent MRI examination prior to and after chemotherapy but prior to surgery. A 1.5-T scanner was used to obtain T1, ADC and DCE-MRI data. DCE-MRI data were analyzed by the FXR model returning estimates of K(trans) (volume transfer constant), v(e) (extravascular extracellular volume fraction) and tau(i) (average intracellular water lifetime). Histogram and correlation analyses assessed parameter changes post-treatment.

RESULTS

Significant (P < .05) changes or trends towards significance (P < .10) were seen in all parameters except tau(i), although there was qualitative reduction in tau(i) values post-treatment. In particular, there was reduction (P < .035) in voxels with K(trans) values in the range 0.2-0.5 min(-1) and a decrease (P < .05) in voxels with ADC values in the range 0.99 x 10(-3) to 1.35 x 10(-3) mm2/s. ADC and v(e) were negatively correlated (r = -.60, P < .02). Parameters sensitive to water distribution and geometry (T(1), v(e), tau(i) and ADC) correlated with a multivariable linear regression model.

CONCLUSION

The analysis presented here is sensitive to longitudinal changes in breast tumor status; K(trans) and ADC are most sensitive to these changes. Relationships between parameters provide information on water distribution and geometry in the tumor environment.

Angiogenesis and antiangiogenic therapy in hematologic malignancies

Angiogenesis, the generation of new blood capillaries from preexisting blood vessels, is tightly regulated in the adult organism. Although many of the initial studies were performed on solid tumors, increasing evidence indicates that angiogenesis also plays an important role in hematologic malignancies. Overexpression of angiogenic factors in particular VEGF and bFGF in most hematologic malignancies may explain the increased angiogenesis found in these malignancies and correlate with poor prognosis as well as decreased overall survival. In this review, we focus on the current literature of angiogenesis and antiangiogenic therapy in hematologic malignancies, and finally describe advances and potential challenges in antiangiogenic treatment in hematologic malignancies.

Angiogenesis-independent tumor growth mediated by stem-like cancer cells

In this work, highly infiltrative brain tumors with a stem-like phenotype were established by xenotransplantation of human brain tumors in immunodeficient nude rats. These tumors coopted the host vasculature and presented as an aggressive disease without signs of angiogenesis. The malignant cells expressed neural stem cell markers, showed a migratory behavior similar to normal human neural stem cells, and gave rise to tumors in vivo after regrafting. Serial passages in animals gradually transformed the tumors into an angiogenesis-dependent phenotype. This process was characterized by a reduction in stem cells markers. Gene expression profiling combined with high throughput immunoblotting analyses of the angiogenic and nonangiogenic tumors identified distinct signaling networks in the two phenotypes. Furthermore, proinvasive genes were up-regulated and angiogenesis signaling genes were down-regulated in the stem-like tumors. In contrast, proinvasive genes were down-regulated in the angiogenesis-dependent tumors derived from the stem-like tumors. The described angiogenesis-independent tumor growth and the uncoupling of invasion and angiogenesis, represented by the stem-like cancer cells and the cells derived from them, respectively, point at two completely independent mechanisms that drive tumor progression. This article underlines the need for developing therapies that specifically target the stem-like cell pools in tumors.