A patient with metastatic colorectal cancer develops a grade 2 acneiform skin rash on the face and upper trunk after starting cetuximab (anti-EGFR monoclonal antibody). The oncologist should interpret this rash as:
- A An expected on-target effect of EGFR inhibition in keratinocytes that correlates with better tumor response ✓
- B A sign of cetuximab hypersensitivity requiring immediate drug discontinuation
- C Evidence of secondary bacterial infection requiring oral antibiotics
- D A sign of hepatic dysfunction from cetuximab metabolism
Correct answer: A. An expected on-target effect of EGFR inhibition in keratinocytes that correlates with better tumor response
Explanation
Acneiform rash is the most common toxicity of EGFR inhibitors (cetuximab, panitumumab, erlotinib) due to EGFR expression in basal keratinocytes and sebaceous glands. Multiple studies show rash severity correlates positively with response and survival. It is managed supportively, not with drug discontinuation unless severe. It is not infectious or hepatically mediated.
Reference: Cancer Chemotherapy, Immunotherapy and Biotherapy, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.