Lack of correlation between epidermal growth factor receptor status and response to Panitumumab monotherapy in metastatic colorectal cancer.

Abstract

PURPOSE:

Panitumumab, a fully human anti-epidermal growth factor receptor (EGFR) monoclonal antibody, is approved as monotherapy for the treatment of metastatic colorectal cancer. We evaluated the association of tumor EGFR expression levels with outcomes in patients with chemorefractory metastatic colorectal cancer.

EXPERIMENTAL DESIGN:

Two phase II, multicenter, single-arm, open-label studies enrolled chemorefractory patients with tumors expressing low/negative (1-9%/<1%; Low/Negative EGFR study) or high (> or =10%; High EGFR study) levels of EGFR. Patients received panitumumab 6 mg/kg every two weeks until disease progression or intolerance. End points included objective response rate (per response evaluation criteria in solid tumors), progression-free survival (PFS), overall survival (OS), and safety. Exploratory analyses by tumor KRAS status were carried out.

RESULTS:

A total of 203 patients (Low/Negative EGFR) and 185 patients (High EGFR) enrolled in the studies. The overall response rate was 5.7% [95% confidence interval (95% CI), 2.6-10.5] in patients with low/negative EGFR and 4.2% (95% CI, 1.6-9.0) in patients with high EGFR; the response rate at week 16 was 4% in both studies (all partial responses). Median PFS times were 8.1 weeks (95% CI, 7.1-12.6), 8.1 weeks (95% CI, 7.4-11.1), and 7.3 weeks (95% CI, 7.1-7.6) in patients with negative, low, and high levels of EGFR expression, respectively. PFS and OS were longer in patients with wild-type KRAS than those with mutant KRAS. As expected, most adverse events were skin related.

CONCLUSIONS:

These studies confirm previous reports that tumor EGFR expression levels are not associated with efficacy with an anti-EGFR antibody and that anti-EGFR antibody therapy should be limited to those patients whose tumors express wild-type KRAS.

• Authors: J Randolph Hecht, Edith Mitchell, Marcus A Neubauer, Howard A Burris 3rd, Paul Swanson, Timothy Lopez, Glenn Buchanan, Maureen Reiner, Jennifer Gansert, Jordan Berlin
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 16 Issue 7 Pg. 2205-13 (Apr 01 2010) ISSN: 1557-3265 [Electronic] United States
• PMID: 20332321 (Publication Type: Clinical Trial, Phase II, Journal Article, Multicenter Study, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2010 AACR.

Chemical References

• Antibodies, Monoclonal
• Antineoplastic Agents
• Biomarkers, Tumor
• Panitumumab
• ErbB Receptors

Topics

• Adult
• Aged
• Aged, 80 and over
• Antibodies, Monoclonal (adverse effects, therapeutic use)
• Antineoplastic Agents (adverse effects, therapeutic use)
• Biomarkers, Tumor (metabolism)
• Carcinoma (diagnosis, drug therapy, metabolism, pathology)
• Colorectal Neoplasms (diagnosis, drug therapy, metabolism, pathology)
• ErbB Receptors (metabolism)
• Female
• Humans
• Male
• Middle Aged
• Neoplasm Metastasis
• Panitumumab
• Predictive Value of Tests
• Prognosis
• Treatment Outcome
• Young Adult