Pancreatic ductal adenocarcinoma, also known as pancreatic cancer, is an eighth cause of cancer-related deaths in the world. The estimated worldwide incidence of pancreatic cancer was 277,000 cases and an estimated 266,000 patients died from the disease in 20081.~Pancreatic cancer is more common in elderly persons than in younger persons, and characterised by early locoregional spread and distant metastasis. As a result, less than 20% of patients are diagnosed with localized, potentially curable disease, and the median survival is no longer than 3-4 months without effective treatment2.~Single-agent chemotherapy with gemcitabine was considered as standard of care for patients with advanced pancreatic cancer, since Burris et al. demonstrated superiority of gemcitabine over 5-fluorouracil (5-FU) in respect of a survival benefit as well as an improvement in disease related symptoms in a randomized study3.~Nevertheless, the activity of gemcitabine monotherapy in pancreatic cancer was modest, and there was a clear need to improve its efficacy by combining it with other anticancer drugs.~Multiple agents such as 5-FU4, capecitabine5,6, cisplatin7,8, oxaliplatin9, pemetrexed10, irinotecan11, cetuximab12, and bevacizumab13, in combination with gemcitabine have been tested in clinical trials, however, they have failed to improve the outcome.~The only agent that, in combination with gemcitabine, has shown a small, but statistically significant improvement, with a hazard ratio (HR) of 0.82, the absolute improvement in median overall survival (OS) of 5.9 months with gemcitabine versus 6.2 months with the combination, is erlotinib, a small-molecule inhibitor of the epidermal growth factor receptor (EGFR)14. Considering the modest improvement in survival by adding erlotinib to gemcitabine, new combination therapy that have a great impact is urgently needed.~S-1 is an oral fluoropyrimidine derivative that combines tegafur (FT) with two modulators; 5-chloro-2, 4-dihydroxypyridine (CDHP) and oteracil potassium (Oxo) in a 1:0.4:1 molar concentration ratio. The phase II trials of a combination of gemcitabine and S-1 have demonstrated objective response rates of 32-48% and median survival of 8-12 months 15-17.~Therefore, we will conduct a phase II study of gemcitabine, erlotinib, and S-1 as first-line chemotherapy in patients with advanced pancreatic cancer and evaluate the EGFR expression, KRAS mutation, and BRAF mutation as predictive or prognostic markers.
This study will conduct a phase II study of gemcitabine, erlotinib, and S-1 as first-line chemotherapy in patients with advanced pancreatic cancer and evaluate the EGFR expression, KRAS mutation, and BRAF mutation as predictive or prognostic markers