A patient with metastatic colorectal cancer on cetuximab develops a severe acneiform rash over the face and trunk. The clinical significance of this rash is that it:

• A Indicates a hypersensitivity reaction requiring immediate drug withdrawal
• B Correlates with better tumour response and improved survival ✓
• C Predicts development of interstitial lung disease
• D Signals that the tumour carries a KRAS mutation

Explanation

The acneiform papulopustular rash of EGFR-targeted antibodies reflects pharmacological inhibition of EGFR in the skin and hair follicles, and multiple studies show that patients developing the rash have higher response rates and longer survival than those who do not. Management is supportive with topical steroids, antibiotics and dose modification, not withdrawal. Interstitial lung disease is a rare unrelated toxicity, and rash severity has no relationship to KRAS mutation status, which must be tested separately on tumour tissue.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.