S-1 in the treatment of pancreatic cancer.

S-1 is an oral 5-fluorouracil (5-FU) prodrug, which is designed to improve the antitumor activity of 5-FU by inhibiting dihydropyrimidine dehydrogenase, the key enzyme of 5-FU catabolism. Recently, two important studies on the clinical use of S-1 for pancreatic cancer have been reported from Japan. In the first study (GEST study), S-1 demonstrated non-inferiority to gemcitabine (GEM) in overall survival (OS) for metastatic or locally advanced pancreatic cancer, but combination chemotherapy with GEM and S-1 did not show superiority to GEM in OS. In the second study (JASPAC-01 study), S-1 showed superiority to adjuvant chemotherapy with GEM in OS in patients with resected pancreatic cancer. In addition to GEM, S-1 is now regarded as the key drug in the management of pancreatic cancer in Japan. To date, many studies have investigated the effectiveness of S-1 in various settings, such as first-line chemotherapy for metastatic or locally advanced pancreatic cancer, second-line chemotherapy after GEM failure, and chemoradiotherapy for locally advanced disease. In this review, we focus on recent clinical trials of S-1-based chemotherapy for advanced pancreatic cancer.