[A case of appearance of a prominent rash in response to alternate-day S-1 administration as adjuvant chemotherapy for lower gingival cancer].

We report the development of a prominent rash in response to alternate-day S-1 administration in a patient with oral cancer. The patient was a 75-year-old woman with left-side lower gingival cancer(T4N1M0). After chemoradiotherapy, the patient underwent radical surgery. She was treated with oral S-1, administered on alternate days at a dosage of 80mg/day (orally, twice per day), as postoperative adjuvant chemotherapy. Edematous erythema, accompanied by strong itching and paraesthesia, appeared focally on the face and the limbs 1 month after beginning S-1 treatment. Since the rash was determined to be drug-induced, S-1 administration was stopped, and steroid, antihistamine, and topical steroid treatment was initiated. The symptoms gradually improved, and the rash disappeared without recurrence approximately 1 month later. Although alternate-day administration is considered to be a safe and effective method to administer S-1 oral therapy, it should be noted that cutaneous symptoms might appear after a fixed dosage is exceeded.