Predictors of Tumor Response to Cetuximab and Panitumumab in 116 Patients and a Review of Approaches to Managing Skin Toxicity.

INTRODUCTION AND OBJECTIVES Cetuximab and panitumumab are monoclonal antibodies that target the epidermal growth factor receptor (EGFR) in the treatment of metastatic colorectal cancer. Most patients develop a papulopustular rash, which may predict tumor response. We studied whether the other adverse cutaneous effects associated with these monoclonal antibodies are also clinical predictors of response. We also reviewed publications describing approaches to treating the papulopustular rash since no evidence-based guidelines have yet been published. MATERIAL AND METHODS We performed a retrospective study of 116 patients with metastatic colorectal cancer receiving anti-EGRF therapy with cetuximab or panitumumab at Hospital Universitario Donostia. RESULTS In total, 81.9% of the patients developed a papulopustular rash. Patients who received the most cycles of treatment with the EGFR inhibitor were at the highest risk of developing the rash, and these patients also had the most severe rash reactions (P=.03). All of the patients who exhibited a complete tumor response had the rash, and the incidence of rash was lower in patients with poor tumor response (P=.03). We also observed an association between tumor response and xerosis (53.4% of the patients who developed xerosis also exhibited tumor response, P=.002). The papulopustular rash was managed according to an algorithm developed by our department. CONCLUSIONS Severe papulopustular rash and xerosis may be clinical predictors of good response to anti-EGFR therapy. Patients who develop a papulopustular rash should be treated promptly because suboptimal treatment of this and other adverse effects can lead to delays in taking the prescribed anti-EGFR dose or to interruption of therapy.