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S‐1 induced a durable response in metastatic extramammary Paget's disease

Dear Editor, We report the case of an 81-year-old man with a 3-year history of extramammary Paget’s disease (EMPD) in his scrotum. He received a wide local resection of the primary lesion and left inguinal lymph node dissection and irradiation in 2006. In February 2008, he underwent lymph node dissection and irradiation for the right inguinal node metastasis. Because a new lymph node metastasis was detected around the aorta in November 2008, docetaxel (60 mg/m) was administrated. After one course, however, this regimen was stopped because of severe neutropenia (grade 4). Although he was under observation without therapy, the level of serum carcinoembryonic antigen (CEA) was gradually increased. Nine months after the administration of docetaxel, he complained of pain due to deteriorated edema and erythema in his thigh, and the CEA was increased to 100 ng/mL (normal range, <4 ng/mL) (Fig. 1). Because of the patient’s low renal function (creatine clearance, 33 mL/min), a lower dose (40 mg/body per day) of tegafur, gimeracil and oteracil potassium (S-1) was p.o. administrated for 2 weeks, and the regimen was repeated with an intermission of 1 week. After two courses, pain, erythema and the edema of his thigh was slightly improved, and the level of serum CEA was decreased to 13.1 ng/mL. Although mild anemia and fatigue were observed, the patient’s performance status (Eastern Cooperative Oncology Group) was 0 and his quality of life was fully maintained during therapy. At 36 months after the beginning of S-1, enlargement of the lymph nodes around the iliac artery and aorta were detected with the elevated level of CEA up to 60 ng/mL. S-1 was stopped in December 2012 because of hydronephrosis caused by enlargement of the metastatic lymph nodes. The total duration of the chemotherapy with S-1 was 40 months. The availability of systemic chemotherapy for advanced EMPD is limited because of disease rarity. Some regimens for metastatic EMPD have been reported, including docetaxel and cisplatin-based combinations. However, EMPD is frequently seen in elderly patients over 80 years old who do not have enough organ capacity to endure severe chemotherapy. S-1 is an oral fluoropyrimidine comprising tegafur, 5-chloro-2,4dihydroxypyridine and potassium oxonate, which was designed to enhance the efficacy of tegafur, a prodrug of fluorouracil. S-1, used as a monotherapy or in combination, has recently attracted attention because of its clinical effect in advanced visceral malignancies including gastric cancer and biliary duct cancer. The toxicity of S-1 is usually limited. The p.o. administration also has benefits. The regular dose of S-1 is 80– 120 mg/day, but a lower dose of 40 mg was given in our patient because of low renal function. Still, durable control was observed. Oral monotherapy of S-1 may be an alternative as palliative therapy, especially in elderly patients with organ deficiencies.