Synergy between cetuximab and chemotherapy in tumors of the gastrointestinal tract

Cetuximab is a recently approved monoclonal antibody that targets the epidermal growth factor receptor, a receptor tyrosine kinase involved in the development and progression of colorectal cancer (CRC) and other solid tumors. Cetuximab, as a single agent or in combination with chemotherapy, has demonstrated significant clinical efficacy against CRC. Combinations of cetuximab with chemotherapy have proven to be well tolerated, with minimal overlap of toxicities between agents; and the anticancer synergy between cetuximab and traditional chemotherapy agents has made cetuximab a vital treatment for patients who are no longer responsive to chemotherapy alone. The U.S. Food and Drug Administration approved cetuximab in combination with irinotecan for the treatment of irinotecan-refractory metastatic CRC or as monotherapy for treating patients intolerant to irinotecan. Combination chemotherapies involving cetuximab as well as combinations involving cetuximab and other targeted agents, such as bevacizumab, an anti-vascular endothelial growth factor monoclonal antibody, constitute powerful new treatment options for the management of CRC. This review discusses recent clinical studies that have further defined this synergy, focusing primarily on tumors of the gastrointestinal tract.

Third-line therapy for metastatic colorectal cancer

BACKGROUND

The past years' therapy for colorectal cancer has evolved rapidly with the introduction of novel cytotoxic agents such as irinotecan, capecitabine and oxaliplatin. Further advances have been achieved with the integration of targeted agents such as bevacizumab, cetuximab and recently, panitumumab. As a result, third-line treatment is now a necessary step in the optimal treatment of patients with metastatic colorectal cancer (MCRC).

MATERIALS AND METHODS

We conducted a literature review of English language publications on third-line therapy for MCRC from January 2000 to April 2007. Data on median overall survival (mOS), median time to progression (mTTP) and response rate were recorded.

RESULTS

We found 27 articles and 22 abstracts to fulfil the criteria. Patients who received regimens containing oxaliplatin and infusional 5-fluorouracil (5-FU) demonstrated mTTP up to 7 months and a mOS of 16 months. With irinotecan and 5-FU, mOS around 8 months were reported and with cetuximab combined with irinotecan, the highest mOS was 9.8 months.

CONCLUSION

Third-line therapy in advanced colorectal cancer may improve mOS for patients with MCRC. Therefore, randomized studies should be conducted in the future.

EGFR-targeted therapies in colorectal cancer

The management of colorectal cancer relies heavily on the combination of the pyrimidine analog antimetabolite 5-fluorouracil with the platinum-based drug oxaliplatin or the topoisomerase inhibitor irinotecan. Optimization of dosing and scheduling of these agents to improve response and survival continues to evolve. Meanwhile, the rational targeting of molecular signaling pathways that are involved in the etiology of malignancies is currently one of the most promising strategies in novel anticancer drug development. New classes of drugs that target the epidermal growth factor receptor are among the most clinically advanced molecular-targeted therapies and have shown efficacy in colorectal cancer. The current status of epidermal growth factor receptor-targeted therapeutic agents is reviewed, with emphasis on their role in the management of colorectal cancer.

Update on capecitabine in colorectal cancer

In combination chemotherapy for metastatic colorectal cancer, i.v. 5-fluorouracil (5-FU) can be replaced by oral 5-FU (in the form of capecitabine or another orally available analogue) without negatively affecting overall toxicity and without remarkably reducing the efficacy of treatment in terms of response rate or overall survival. Preclinical evidence of synergy has led to promising early and successfully completed studies combining capecitabine plus oxaliplatin with bevacizumab, cetuximab, and epidermal growth factor receptor tyrosine kinase inhibitors. The use of preoperative capecitabine plus radiation is achieving good rates of pathological complete response in rectal cancer. While capecitabine is generally well tolerated, its potential toxicities need careful management and may require individual dose adaption.

Clinical Activity of Pertuzumab (rhuMAb 2C4), a HER Dimerization Inhibitor, in Advanced Ovarian Cancer: Potential Predictive Relationship With Tumor HER2 Activation Status

Purpose

Ovarian cancers (OCs) frequently have HER2 activation in the absence of HER2 overexpression. Pertuzumab, a humanized antibody that prevents HER2 dimerization and inhibits multiple HER-mediated pathways, was studied in a phase II, multicenter trial in advanced, refractory OC.

Patients and Methods

Sixty-one patients (cohort 1) with relapsed OC received a loading dose of 840 mg pertuzumab intravenously followed by 420 mg every 3 weeks; 62 patients (cohort 2) received 1,050 mg every 3 weeks. Response rate was the primary end point. Fresh tumor biopsies were obtained in cohort 1 to assay for phosphorylated HER2 (pHER2).

Results

Median age was 57 years and median number of prior chemotherapy regimens was five. Fifty-five patients in cohort 1 and 62 patients in cohort 2 were assessable for efficacy. There were five partial responses (response rate [RR] = 4.3%; 95% CI, 1.7% to 9.4%), eight patients (6.8%) with stable disease (SD) lasting at least 6 months, and 10 patients with CA-125 reduction of at least 50% (includes two partial responses and four patients with SD ≥ 6 months; total clinical activity, 14.5%). Median progression-free survival (PFS) was 6.6 weeks. Eight of 28 tumor biopsies (28.6%) were pHER2+ by enzyme-linked immunosorbent assay (ELISA; without gene amplification). Median PFS for pHER2+ patients was 20.9 weeks (n = 8) versus 5.8 weeks for pHER2− (n = 20; P = .14) and 9.1 weeks for unknown pHER2 status (n = 27). Pertuzumab was well tolerated with diarrhea in 69.1% (11.4% grade 3, no grade 4). Five patients had asymptomatic left ventricular ejection fraction decreases to less than 50% (one confirmed by central facility).

Conclusion

Pertuzumab is well tolerated with a RR of 4.3% in heavily-pretreated OC patients. Further studies on pHER2 as a diagnostic are warranted.

Hypersensitivity reactions associated with oxaliplatin

The reported incidence of hypersensitivity reactions (HSRs) associated with oxaliplatin in patients with colorectal cancer (CRC) is approximately 12%, with 1 - 2% of patients developing grade 3 or 4 in severity. However, the recent rising incidence of HSR to oxaliplatin observed is the result of increasing clinical use. HSR to oxaliplatin may manifest as facial flushing, rash/hives, tachycardia, dyspnoea, erythema, pruritus, fever, tongue swelling, headache, chills, weakness, vomiting, burning sensations, dizziness and oedema. Anaphylactic shock is rare but serious, and must be considered in the event of hypotension. No definitive approaches to prevent and treat HSR associated with oxaliplatin are available; however, few successful strategies have been reported. Such strategies include: slowing the infusion rate, use of steroids and antagonists of type 1 and 2 histamine receptors, and desensitisation. Successful implementation of oxaliplatin desensitisation protocols based on other platinum-containing compounds have been reported, which could enable a small number of patients who experience severe HSR to further receive an effective therapy for CRC. However, reintroductions have only been reported as single case studies or small cohorts. Large-scale validation on desensitisation strategies are still missing. Recently, subcutaneous adrenaline has also been utilised as an alternative approach to manage HSR to oxaliplatin. Knowledge of this rare but real toxicity of oxaliplatin is paramount because the use of this drug continues to increase not only for the treatment of patients with stage II-IV CRC, but also other solid malignancies. In this article, the author discusses the incidence, clinical presentation, pathogenesis, risk factors and current strategies of management of HSR associated with oxaliplatin.

Targeting the Epidermal Growth Factor Receptor in the Treatment of Colorectal Cancer

The epidermal growth factor receptor (EGFR) is an important mediator of normal cellular processes such as growth, survival, differentiation and morphogenesis. Disturbances in the EGFR pathway have been associated with the development and progression of malignancy, including cellular proliferation, angiogenesis, invasion/metastasis and anti-apoptosis, as well as with resistance to chemotherapy and/or radiation therapy. As a result, this is an excellent rationale for treatment with EGFR-specific therapeutic agents. These agents may be EGFR-targeted antibodies or small molecules that inactivate the receptor tyrosine kinase. While only cetuximab has received US FDA approval for the treatment of colorectal cancer, numerous agents are currently in development and in clinical trials and constitute an area of intensive, ongoing research.