3. Adjuvant therapy and outcomes

Adequate adjuvant therapy was defined as receiving ≥4 cycles of chemotherapy with or without radiation. Chemotherapeutic regimens included gemcitabine monotherapy (intravenous gemcitabine at 1,000 mg/m² over 30 minutes on days 1, 8, and 15, followed by 1-week rest), gemcitabine plus erlotinib (intravenous gemcitabine at 1,000 mg/m² over 30 minutes on days 1, 8, and 15, plus oral erlotinib at 100 mg daily for 28 days), and 5-fluorouracil plus leucovorin (bolus intravenous leucovorin at 20 mg/m² followed by bolus intravenous 5-fluorouracil at 425 mg/m² on days 1–5 every 4 weeks). The outcomes were defined as disease-free survival (DFS; time from surgery to the first instance of recurrence or the date of last follow-up) and overall survival (OS; time from diagnosis to death or the date of last follow-up).