The Double-Edged Sword of Epidermal Growth Factor Receptor Inhibitor: Rash as Toxicity and Prognostic Marker

A 50-year-old man undergoing treatment with the epidermal growth factor receptor inhibitor (EGFRI) lapatinib for stage 2 breast carcinoma developed a papulopustular rash, a common side effect of EGFRIs, affecting 50-100% of patients. This rash, part of the 'PRIDE' complex, includes various cutaneous adverse effects such as xerosis and eczema. The patient was treated with doxycycline and hydrocortisone cream, showing significant improvement within a week. Acneiform eruptions, which lack comedones, may serve as a potential marker for therapeutic response to EGFRI drugs, although evidence is inconsistent. The rash typically appears within 1-2 weeks of therapy, peaks at 3-4 weeks, and subsides gradually. Patients are advised on sun protection and gentle skincare to manage symptoms.