While 3-weekly S-1 plus cisplatin (SP3) provided a slight progression-free survival advantage over 5-weekly S-1 plus cisplatin (SP5), there was no difference in overall survival and either can be used as first-line treatments for patients with advanced gastric cancer, according to a story published online ahead of print in the Annals of Oncology.

In a phase 3 Japanese study, researchers compared SP3 (S-1 80 mg/m2/day on days 1-14 and cisplatin 60 mg /m2 on day 1) with SP5 (S-1 80-120 mg/day on days 1-21 and cisplatin 60 mg/m2 on day 1 or 8) in terms of progression-free survival advantage.

Between February 2009 and January 2012, a total of 625 chemotherapy-naïve patients with metastatic, recurrent gastric or gastroesophageal junction adenocarcinoma were randomly assigned to either arm.

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Median follow-up was 32.4 months. Results showed that progression free survival was superior in the SP3 arm (5.5 months vs. 4.9 months), but there was no difference in overall survival (14.1 months vs. 13.9 months). The response rates were 60% and 50% in SP3 and SP5, respectively.

In regard to safety, both were well tolerated. Grade 3 or higher anemia (19.9% vs. 9%) and neutropenia (39% vs. 9%) occurred more often in the SP3 group.


  1. Ryu M-H, Baba E, Lee KH, et al. Comparison of two different S-1 plus cisplatin dosing schedules as first-line chemotherapy for metastatic and/or recurrent gastric cancer: a multicenter, randomized phase 3 trial (SOS). Ann Oncol. [epub ahead of print]. 2015. doi: 10.1093/annonc/mdv316.