Updated results from GEST study: a randomized, three-arm phase III study for advanced pancreatic cancer

Purpose The GEST study showed non-inferiority of S-1 but not superiority of gemcitabine plus S-1 (GS) to gemcitabine alone for overall survival with the data by the cut-off date of 31st July in 2010 for chemo-naïve patients with advanced pancreatic cancer. We considered it important to determine whether S-1 maintains non-inferiority after a long-term follow-up in the GEST study and to obtain a firm positive conclusion. In addition, it may be an interesting challenge to explore the efficacious profile of GS in the long-term follow-up study. Using the data from the follow-up period, background and efficacy in patients from Taiwan and Japan, as well as the rates of tumor shrinkage in locally advanced and metastatic patients (Waterfall plot) were also analyzed. Methods The results of the primary analysis were reconfirmed, and subset analysis of overall survival and progression-free survival was performed based on the overall survival data updated by the cut-off date of 31st July in 2011. Results The median follow-up period was 29.8 months, and 795 deaths occurred (95.6%). The median overall survival was 8.8 months for gemcitabine, 9.7 months for S-1 (hazard ratio [HR], 0.96; 97.5% confidence interval [CI], 0.79–1.17), and 9.9 months for GS (HR 0.91; 97.5% CI 0.75–1.11). In patients with performance status (PS) 0, the median overall survival was 9.8 months for gemcitabine, 10.9 months for S-1, and 10.5 months for GS. In patients with PS 1, the median overall survival was 6.2 months for gemcitabine, 6.3 months for S-1, and 9.6 months for GS. Conclusion Our survey reconfirmed the non-inferiority of S-1 to gemcitabine and showed S-1 can be used as one of the standard treatment options for advanced pancreatic cancer. Trial registration ClinicalTrials.gov: NCT00498225. Electronic supplementary material The online version of this article (doi:10.1007/s00432-017-2349-y) contains supplementary material, which is available to authorized users.