Updated results of the GEST study: Randomized phase III study of gemcitabine plus S-1 (GS) versus S-1 versus gemcitabine (GEM) in unresectable advanced pancreatic cancer in Japan and Taiwan.

Abstract

4035 Background: The GEST study (Ioka et al. ASCO 2011, Abstract 4007) demonstrated the non-inferiority of S-1 to GEM with respect to the primary endpoint of overall survival (OS) in patients with pancreatic cancer (PC). We now report the updated results of this study. Methods: The GEST study was a randomized, 3-arm, phase III study. Chemotherapy-naive patients with unresectable advanced PC, an ECOG Performance status (PS) of 0-1, and adequate organ functions were randomly assigned to receive GEM (1000 mg/m2, iv, d1, 8 and 15, q4w), S-1 (80/100/120 mg/day based on BSA, po, d1-28, q6w), or GS (GEM 1000 mg/m2, iv, d1 and 8 plus S-1 60/80/100 mg/day based on BSA po, d1-14, q3w). The primary endpoint was OS, used to assess the non-inferiority of S-1 and the superiority of GS to GEM. Patient information was updated in July 2011. Results: At the time of this follow-up analysis, median follow-up was 29.8 months with 795 OS events, compared with 18.4 months with 710 OS events out of 832 patients at the previous analysis. Median OS was 8.8 months (95% CI: 8.0–9.7) in the GEM group and 9.7 months (95% CI: 7.6-10.8) in the S-1 group (HR=0.96, 97.5% CI: 0.79-1.17, p<0.001 for non-inferiority), which is consistent with prior results (HR=0.96, 97.5% CI: 0.78-1.18, p<0.001). In the GS group, median OS was 9.9 months (95% CI: 9.0-11.2). The HR was 0.91 (97.5%CI: 0.75-1.11, p=0.28 for superiority versus the GEM group). On subgroup analysis, GS was associated with a non-statistically significant trend toward better OS compared with GEM among patients with locally advanced disease and those with a PS of 1. Median OS was 12.7 months (95% CI: 9.7–14.9) in the GEM group and 15.9 months (95% CI: 13.0-19.7) in the GS group (HR=0.72, 95% CI: 0.51-1.03) among patients with locally advanced disease, and 6.2 months (95% CI: 4.9–8.3) in the GEM group and 9.6 months (95% CI: 8.0-10.9) in the GS group (HR=0.62, 95% CI: 0.46-0.83) among patients with a PS of 1. Conclusions: The non-inferiority of S-1 to Gem in terms of the primary endpoint of OS was reconfirmed. Monotherapy with S-1 can be used as one of the standard treatments for advanced PC. As for GS therapy, there is room for further investigation.