Treatment and study design

The treatment consisted of intravenous administration of gemcitabine at 1,000 mg/m² on days 1 and 8 every 3 weeks, continuously orally administered erlotinib at 100 mg/day, and orally administered S-1 at 30 mg/m² twice daily on days 1-14 of each cycle. Patients with a body surface area of <1.25 m² received 80 mg of S-1 daily, those with a body surface area of 1.25-1.5 m² received 100 mg of S-1 daily, and those with a body surface area of ≥1.5 m² received 120 mg of S-1 daily. Treatment was delivered as a 3-week cycle and repeated up to a maximum of 8 cycles of chemotherapy, or until disease progression, unacceptable toxicity, or the patient's refusal.

This trial was a prospective, single-arm phase II study evaluating combination chemotherapy with gemcitabine, erlotinib, and S-1 in previously untreated patients with unresectable locally advanced or metastatic pancreatic cancer. The primary endpoint was the confirmed objective response rate (ORR), and the secondary endpoints were median progression-free survival (PFS), median overall survival (OS), disease control rate (DCR), and toxicity profiles. The investigation was performed in accordance with the Declaration of Helsinki, and the protocol was approved by the institutional review boards of Hallym University Medical Center, Anyang-si, South Korea, and Asan Medical Center, Seoul, South Korea (protocol number: HMC-HO-GI-1201).