A double-blind, placebo-controlled study evaluating the efficacy and safety of vitamin K1 ointment for the treatment of patients with cetuximab-induced acneiform eruption has started. Vitamin K1 ointment and placebo are applied twice daily for 8 consecutive weeks after the development of acneiform eruptions. Vitamin K1 ointment is applied in the middle of one side (face, neck or chest) and placebo is applied to the other side. The primary endpoint is the regression rate of acneiform eruptions on right- and left-side lesions in the same patient, compared with baseline at the final evaluation in the 10-week trial. The secondary endpoints include adverse events of acneiform eruption and other adverse events.