Irinotecan has a strong growth-inhibiting effect on cultured pancreatic adenocarcinoma cells. It is also highly active on pancreatic tumor cells in culture and in xenograft models. Irinotecan monotherapy has been tested in patients with previously untreated pancreatic cancer, yielding response rates of 9-27%. In vitro studies indicate that synergism between irinotecan and 5-FU is sequence dependent, cytotoxicity is being stronger when irinotecan is administered before 5-FU. Recently, French study group reported that FOLFIRI.3 regimen, comprising of irinotecan D1 and D3 with 5-FU for 2 days from D2, has promising activity in chemotherapy-naïve and pretreated patients with advanced pancreatic cancer. The confirmed response rate was 37.5% with a median progression-free survival of 5.6 months. The study also suggested no cross-resistance between gemcitabine and FOLFIRI.3.