S-1-induced, prolonged complete regression of lung metastasis from gastric cancer refractory to 5'-DFUR: a case report with pharmacokinetic study.

S-1 is an oral fluoropyrimidine reported to be most active for gastric cancer. However, few studies have documented a complete response (CR) of lung metastasis to S-1 treatment. We describe a 66-year-old woman in whom S-1 induced complete regression of lung metastasis from gastric cancer, that had been refractory to another oral fluoropyrimidine, 5'-deoxy-5-fluorouridine (5'-DFUR). After preoperative chemotherapy with a combination of etoposide, adriamycin and cisplatin and with methotrexate plus 5-fluorouracil, the patient underwent a total gastrectomy with lower esophagectomy for advanced diffuse-type gastric cancer with invasion of the esophagus in May 1993. She received postoperative adjuvant chemotherapy with 5'-DFUR (600 mg/day) for 3 years. However, a solitary metastasis to the left lung was detected in November 1996 and she underwent partial resection of the left lung. Chemotherapy with 5'-DFUR was reinitiated after operation, but re-metastasis to the left lung with elevation of the serum carcinoembryonic antigen (CEA) level was diagnosed in June 1999. Treatment with S-1 was started in August. S-1 was given orally in a dose of 100 mg/day for 28 consecutive days, followed by a 14-day recovery; treatment was repeated every 6 weeks. The metastatic lesion in the left lung completely regressed after two courses of S-1 and the serum CEA level returned to the normal range. The patient received a total of 10 courses of S-1. The dose of S-1 was reduced to 80 mg/day from the sixth course because of grade 2 skin rash. Pharmacokinetic studies after administration of S-1 revealed high and prolonged plasma 5-FU levels. Nearly 4 years have passed since complete regression of the lung metastasis. This may be the first report to document a prolonged complete response of lung metastasis from gastric cancer induced by single-agent chemotherapy with S-1.