Targeted Therapies in the Treatment of Colorectal Cancers

Background:

In solid organ malignancies, no tumor type has seen a greater impact from the development of novel targeted therapies in 2004 than metastatic colorectal cancer.

Methods:

We review the current progress to date with the use of monoclonal antibodies in colorectal cancer and look at newer therapies under investigation.

Results:

Two monoclonal antibodies received Food and Drug Administration approval in early 2004, both for the indication of advanced, metastatic colorectal cancer. A large, randomized, placebo-controlled study demonstrated that the addition of a monoclonal antibody to vascular endothelial growth factor, bevacizumab, led to a statistically significant improvement in overall survival, with tolerable additional toxicity. Chimeric monoclonal antibody therapy directed at the epidermal growth factor receptor was associated with radiographic responses in a significant minority of patients with irinotecan-refractory colon cancer in a randomized phase II study of patients with irinotecan-refractory disease.

Conclusions:

These dramatic successes have led to further clinical studies of targeted therapy in colorectal cancer, making it one of the most promising areas of cancer research.

Cetuximab, a chimeric human mouse anti-epidermal growth factor receptor monoclonal antibody, in the treatment of human colorectal cancer

The recent successful development of monoclonal antibodies that target key components of biological pathways has expanded the armamentarium of treatment options for patients with colorectal cancer (CRC). In particular, the epidermal growth factor receptor (EGFR), a tyrosine kinase growth factor receptor involved in CRC development and progression, is exploited by the newest monoclonal antibody that is available for use in CRC patients. Cetuximab, the first chimeric monoclonal antibody, which has been generated against the EGFR, is currently registered in USA, Europe and worldwide, in combination with irinotecan in the treatment of metastatic CRC patients who have progressed on irinotecan containing chemotherapy. Cetuximab is well tolerated and does not exacerbate the toxicity of concomitant chemotherapy. Furthermore, a series of phase III clinical trials are currently evaluating the combination of cetuximab with standard chemotherapy regimens in the first-line treatment chemotherapy-naïve patients with metastatic CRC.

Cetuximab and irinotecan/5-fluorouracil/folinic acid is a safe combination for the first-line treatment of patients with epidermal growth factor receptor expressing metastatic colorectal carcinoma

BACKGROUND

To investigate the safety/tolerability of the EGFR-antibody cetuximab when added to irinotecan/5-fluorouracil (5-FU)/folinic acid (FA) for first-line treatment in patients with metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

Twenty-one patients with untreated, metastatic, EGFR-expressing CRC received cetuximab 400 mg/m(2) as an initial dose, and thereafter 250 mg/m(2) weekly. In addition, patients received infusional 5-FU (24 h) in two dose levels (1500 mg/m(2), low 5-FU group, n = 6 or 2000 mg/m(2), high 5-FU group, n = 15), plus FA at 500 mg/m(2) and irinotecan at 80 mg/m(2), weekly x6 q50d.

RESULTS

Twenty patients were assessable for tolerability after the first cycle. There were no dose limiting toxicities (DLTs) in the low 5-FU group and three DLTs (20%) in the high 5-FU group (two patients with diarrhea grade 3 and one patient with diarrhea grade 4). In the low 5-FU group all six patients received >80% of the planned dose. In the high 5-FU group, seven of 14 patients (50%) received < or =80% of the planned chemotherapy dose during the first cycle due to dosage reductions whilst treatment delays occurred in 10/14 patients. During the whole study period, the common grade 3/4 adverse events were acne-like rash (38%) and diarrhea (29%). Chemotherapy did not affect the pharmacokinetics of cetuximab determined at weeks 1 and 4. Fourteen patients (67%, 95% CI 47% to 87%) had a confirmed response, and six (29%) had stable disease. Median time to progression was 9.9 months [lower 95% confidence limit (CL) 7.9, upper 95% CL not reached]. Median survival time was 33 months (lower CL 20, upper CL not reached). Four patients received secondary surgery with curative intent, and a fifth was potentially eligible for surgery but declined.

CONCLUSIONS

Addition of cetuximab to weekly infusional 5-FU/FA plus irinotecan is safe and first data suggest a promising activity. The 5-FU dose of 1500 mg/m(2) is recommended for further studies.

Antibody-based therapies for colorectal cancer

The recent successful development of novel monoclonal antibodies that target key components of biologic pathways has expanded the armamentarium of treatment options for patients with colorectal cancer. Two targets in particular--the process of new blood vessel development, or angiogenesis, and the epidermal growth factor receptor and its signaling pathway--are exploited by the newest monoclonal antibodies that are available for use in colorectal cancer patients. This clinical review focuses on the defining role of the two most clinically advanced novel agents, bevacizumab (Avastin; Genentech, Inc., South San Francisco, CA, http://www.gene.com) and cetuximab (Erbitux; ImClone Systems, Inc., New York, http://www.imclone.com), in colorectal cancer.