Biological mechanisms of bevacizumab-associated adverse events

The perception that inhibition of cancer-associated angiogenesis would be an effective treatment strategy was based on the fundamental difference in cell cycle activity between neoplastic and normal endothelial cells. Selective targeting of tumor vessels could have additional benefits, such as circumventing development of acquired resistance to these types of agents, overcoming intrinsic tumor resistance, exhibiting broad anti-tumor activity and decreasing normal tissue toxicity. Successful translation of anti-angiogenic therapy into the clinical setting was achieved only 5 years ago with the approval of bevacizumab for metastatic colorectal cancer. Although the benefits demonstrated in clinical trials led to the approval of bevacizumab for treatment of colorectal, lung and breast cancers, and most recently glioblastoma, a number of serious soft-tissue and vascular toxicities have also been observed in patients receiving this anti-angiogenic agent. This review assesses the relationship between inhibition of VEGF and toxicity, and proposes the pathogenic mechanisms that lead to the adverse events.

Bowel perforation from bevacizumab for the management of colorectal cancer

Bevacizumab (Avastin) is a recently developed monoclonal antibody, which targets the vascular endothelial growth factor receptor pathway, and is currently used in combination with cytotoxic agents as first-line or second-line therapy for patients with metastatic colon cancer. Common complications from administration of bevacizumab include hypertension, proteinuria, and diarrhea. These complications are typically managed conservatively. More serious complications of bevacizumab administration include venous thromboembolism, bleeding, and bowel perforation. Although these complications are much more infrequent, prompt recognition is imperative for adequate and timely management. In this report, we discuss a patient with bowel perforation from bevacizumab for the treatment of metastatic colorectal cancer.

Intricacies of bevacizumab-induced toxicities and their management

OBJECTIVE

To review the serious and common toxicities of bevacizumab and describe their incidence, risk factors, presentation, pathophysiology, and management.

DATA SOURCES

Literature for this review article was collected from PubMed, MEDLINE, and the proceedings of the American Society of Clinical Oncology (2000-November 2008). The key terms used in the search were: bevacizumab, vascular endothelial growth factor, angiogenesis inhibitors, toxicity, toxicity management, and adverse event.

STUDY SELECTION AND DATA EXTRACTION

Review articles, preclinical studies, and all published Phase 1-3 clinical trials were reviewed. The references listed in identified articles were examined for additional publications.

DATA SYNTHESIS

The biomedical literature from 2000 to 2008 confirms that bevacizumab carries serious and potentially life-threatening toxicity risks and emphasizes the importance of early recognition, continuous monitoring, and prompt management of these toxicities. Such toxicities include hemorrhage/bleeding, wound healing complications, gastrointestinal perforation, arterial thromboembolism, congestive heart failure, hypertension, proteinuria/nephrotic syndrome, infusion-related hypersensitivity reactions, and reversible posterior leukoencephalopathy syndrome. Patients at the highest risk for these toxicities are individuals with a history of hypertension, thromboembolism, bleeding, cardiovascular disease, or preexisting proteinuria, as these conditions may be exacerbated by bevacizumab use. Additionally, particular tumor types correlate with risk for individual toxicities; for example, patients with squamous non-small-cell lung cancer or rectal cancer have a higher risk of bleeding, those with renal cell carcinoma have a higher proteinuria risk, and patients with colorectal cancer have a higher risk of gastrointestinal perforation. Further investigation is warranted to develop effective management strategies for these toxicities.

CONCLUSIONS

As bevacizumab is becoming widely used in general oncology practice, it is important to understand the toxicities that can arise and to develop practice guidelines for their management.

Bowel perforation from bevacizumab for the treatment of metastatic colon cancer: incidence, etiology, and management

Avastin (Bevacizumab) is a recently developed monoclonal antibody against vascular endothelial growth factor (VEGF) receptor that increases survival in patients with metastatic colorectal cancer. Bowel perforation is a known risk factor of unknown etiology associated with the use of Avastin. In this report, the incidence, risk factors, typical presentation, and management of patients with this complication is described.

Paclitaxel-carboplatin alone or with bevacizumab for non-small-cell lung cancer

BACKGROUND

Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, has been shown to benefit patients with a variety of cancers.

METHODS

Between July 2001 and April 2004, the Eastern Cooperative Oncology Group (ECOG) conducted a randomized study in which 878 patients with recurrent or advanced non-small-cell lung cancer (stage IIIB or IV) were assigned to chemotherapy with paclitaxel and carboplatin alone (444) or paclitaxel and carboplatin plus bevacizumab (434). Chemotherapy was administered every 3 weeks for six cycles, and bevacizumab was administered every 3 weeks until disease progression was evident or toxic effects were intolerable. Patients with squamous-cell tumors, brain metastases, clinically significant hemoptysis, or inadequate organ function or performance status (ECOG performance status, >1) were excluded. The primary end point was overall survival.

RESULTS

The median survival was 12.3 months in the group assigned to chemotherapy plus bevacizumab, as compared with 10.3 months in the chemotherapy-alone group (hazard ratio for death, 0.79; P=0.003). The median progression-free survival in the two groups was 6.2 and 4.5 months, respectively (hazard ratio for disease progression, 0.66; P<0.001), with corresponding response rates of 35% and 15% (P<0.001). Rates of clinically significant bleeding were 4.4% and 0.7%, respectively (P<0.001). There were 15 treatment-related deaths in the chemotherapy-plus-bevacizumab group, including 5 from pulmonary hemorrhage.

CONCLUSIONS

The addition of bevacizumab to paclitaxel plus carboplatin in the treatment of selected patients with non-small-cell lung cancer has a significant survival benefit with the risk of increased treatment-related deaths. (ClinicalTrials.gov number, NCT00021060.)

Metastatic colorectal cancer

Metastatic colorectal cancer remains a public-health issue on a global scale. With development of a new generation of cytotoxic agents, survival has improved for patients with metastatic disease. How to maximize the benefit of chemotherapy with acceptable toxicity remains incompletely answered. Hepatic resection can provide a significant hope for long term survival, and a subset of patients might benefit from perioperative approaches. More recently, specific molecular processes have been targeted for therapeutic interventions, and encouraging results have been achieved using inhibitors of the Epidermal Growth Factor Receptor and the Vascular Endothelial Growth Factor.

Management of advanced colorectal cancer: state of the art

Colorectal cancer (CRC) caused over 500 000 deaths worldwide in 2002. Recent advances in the treatment of advanced disease include the incorporation of two new cytotoxic agents, irinotecan and oxaliplatin, into first-line regimens. The concept of planned sequential therapy involving three active agents during the course of a patient's treatment is evolving. Coupled with the integrated use of targeted monoclonal antibodies, we can now expect overall survival rates for advanced disease to exceed 20 months. This review considers current treatments and suggests where future progress may occur.

First- and second-line therapy of metastatic colorectal cancer

In the USA, colorectal cancer is the fourth most prevalent cancer and is the second leading cause of cancer death after lung cancer. In 2006, 148,610 colorectal cancer cases are expected in the USA, with 55,170 deaths expected from this disease. After years of stagnation, the treatment of metastatic colorectal cancer has recently made dramatic advances. The previous standard of care, 5-fluorouracil, is the now the backbone of combination regimens with oxaliplatin or irinotecan. The addition of biological agents, such as the vascular endothelial growth factor inhibitor, bevacizumab, and the epidermal growth factor receptor inhibitors, cetuximab and panitumumab, have further enhanced the activity of conventional chemotherapy. These advances have increased the overall survival of advanced colorectal cancer patients, which was once 6 months with best supportive care, to over 2 years if all active agents are used in the course of the disease.

Incidence and management of bevacizumab-related toxicities in colorectal cancer

Bevacizumab, a recombinant, humanised monoclonal antibody against vascular endothelial growth factor, when used in combination with intravenous 5-fluorouracil (5-FU)-based chemotherapy as first-line treatment of metastatic colorectal cancer (CRC) improves survival. In a randomised, placebo-controlled Phase III study, the addition of bevacizumab to irinotecan/5-FU/leucovorin (IFL) resulted in significant improvement in survival compared with IFL alone, which led to its approval for first-line use in CRC. Bevacizumab also demonstrates improved efficacy in combination with 5-FU/LV over chemotherapy alone when data were pooled from two randomised Phase II studies utilising bevacizumab with 5-FU/leucovorin, and also in a third treatment arm of bevacizumab/5-FU/LV of a randomised Phase III study. More recently, in the second-line setting, bevacizumab in combination with FOLFOX improved survival from 10.8 to 12.9 months in the ECOG 3200 trial. Clinical activity with the addition of bevacizumab to oxaliplatin and either 5-FU or capecitabine-based regimens has also been shown in TREE-2, and activity with the combination of bevacizumab and the EGFR inhibitor cetuximab has been documented in BOND-2. In this study, bevacizumab was generally well-tolerated with no unexpected toxicities when combined with cetuximab. A few toxicities were uniformly encountered in all of the above studies, in particular grade 3 medically-manageable hypertension (3 - 16%). In addition, other toxicities were haemorrhage (2 - 9.3%), gastrointestinal perforation (1.5%), arterial thromboembolism (3.8%), wound healing (1 - 2%) and proteinuria (1 - 2%). As bevacizumab is becoming widely used in general oncology practice, it is important to understand the toxicities which can arise and to develop practice guidelines for their management. This review addresses the toxicities noted in trials using bevacizumab for the treatment of CRC and provides recommendations for toxicity management.

Bevacizumab Combined with Standard Fluoropyrimidine-Based Chemotherapy Regimens to Treat Colorectal Cancer

For several decades, 5-fluorouracil (5-FU) with or without leucovorin defined the standard of care for the treatment of metastatic colorectal cancer (CRC). The addition of other chemotherapy regimens to 5-FU has improved survival, but often at the expense of increased toxicity. Recent advances in our understanding of the molecular basis of CRC have led to the production of novel targeted agents, such as bevacizumab (Avastin). Bevacizumab is currently approved for the first-line treatment of metastatic CRC and is currently being tested in combination with standard therapies for a range of indications. Phase II/III trials have demonstrated that the addition of bevacizumab to 5-FU-based first-line chemotherapy improves survival, progression-free survival and response rate compared with chemotherapy alone. Combination therapy does not appear to exacerbate side effects known to be associated with the chemotherapy regimen. The most common side effects attributable to bevacizumab therapy include hypertension, proteinuria and bleeding. Although uncommon, gastrointestinal perforation and arterial thromobembolic events are the most serious side effects reported to date. Bevacizumab is currently being evaluated in combination with oxaliplatin (Eloxatin)-based therapies and preliminary data are encouraging. Ongoing trials of bevacizumab in combination with standard first-line chemotherapy regimens will evaluate bevacizumab's potential in a range of cancer types. .

Managing patients treated with bevacizumab combination therapy

The anti-angiogenic agent bevacizumab (Avastin) has been rationally designed to target vascular endothelial growth factor (VEGF), a key mediator of tumor angiogenesis. Based on its limited roles in adults, VEGF inhibition using bevacizumab would be expected to have limited side effects. Furthermore, because its mechanism of action is different to that of standard chemotherapeutic agents, bevacizumab would not be expected to cause typical cytotoxic agent-related toxicity or to exacerbate the toxicity of concomitant chemotherapy. We have reviewed clinical trials published to date, primarily in metastatic colorectal cancer, and describe the safety profile of bevacizumab. The review focuses on hypertension, proteinuria, arterial thrombosis, effects on wound healing, bleeding and gastrointestinal (GI) perforation, which are the principal bevacizumab-related events seen in clinical trials. These events are for the most part mild to moderate in severity and clinically manageable (hypertension, proteinuria, minor bleeding) or occur uncommonly (wound healing complications, GI perforations and arterial thrombosis). The side-effect profile of bevacizumab makes it a suitable adjunct to standard chemotherapy in settings where efficacy has been demonstrated, and it is now approved for use in the USA, the European Union and other markets worldwide.