A phase III trial in Japanese patients with stage I-III pancreatic cancer shows that adjuvant treatment with a chemotherapy drug called S-1, substantially increases overall survival rates compared to treatment with the standard postoperative drug gemcitabine. The findings point to a more effective treatment option for a subset of patients with pancreatic cancer, particularly for Asian patients.  The study results were presented at the tenth annual Gastrointestinal Cancers Symposium.

"Our survival data were much stronger than expected. Based on these results, we hope that guidelines for standard postoperative therapy for pancreatic cancer in Japan will be changed to replace gemcitabine with S-1as single-agent therapy," said lead author Katsuhiko Uesaka, M.D., Ph.D., medical deputy director at Shizuoka Cancer Center Hospital. The drug could also be a promising treatment option for Asian patients in other parts of the world. S-1 is currently available in several Asian countries and most of Europe, though it is not yet approved in the United States.  

Because pancreatic cancer is typically detected after it has spread beyond the pancreas, only 20-30 percent of patients are candidates for surgery. Following surgery patients typically receive the adjuvant chemotherapy drug gemcitabine, which has been shown to lengthen survival by several months compared to surgery alone. In Asian patients with inoperable pancreatic cancer, previous studies have suggested that outcomes with S-1 are comparable to outcomes with gemcitabine.  Previous studies have shown that S-1 has more harmful side effects in Caucasian patients.

In the present study, conducted in Japan, investigators randomly assigned 385 patients to postoperative treatment with gemcitabine or S-1. An interim analysis of trial data found that patients who received S-1 had a 44 percent lower risk of death than patients who received gemcitabine. The two-year survival rates were 70 percent and 53 percent for S-1 and gemcitabine, respectively. Relapse rates were also lower in theS-1 arm. The two-year relapse-free survival rates were 49 percent and 29 percent for S-1 and gemcitabine, respectively. S-1 was well tolerated, with over 70 percent of patients completing the therapy.

Based on these interim analysis findings, the safety and efficacy committee that monitors this trial recommended early reporting of the results to speed adoption of S-1 as the new standard postoperative treatment for patients with pancreatic cancer. The investigators will continue to follow the study participants for at least five years.

Due to metabolic differences between Asian and Caucasian ethnic groups, gastrointestinal side effects of S-1 are more severe among Caucasians, requiring use of lower doses of the drug for Caucasian patients. For those reasons, the findings of this study are not immediately applicable to non-Asian populations, but Uesaka hopes that similar studies of S-1 as adjuvant therapy for pancreatic cancer will soon be conducted in Europe and the United States among Caucasian patients, with adjustment of S-1 dose.

S-1 is an oral chemotherapy drug prescribed in Japan to treat stomach, colorectal, pancreatic, biliary, head and neck, non-small cell lung, and metastatic breast cancer.