Effect of the number of cycles of docetaxel + S-1 therapy on long-term survival in adjuvant chemotherapy for stage III gastric cancer. A pooled analysis of the OGSG0604 and OGSG1002 trials

Background S-1 plus docetaxel (DS) therapy followed by S-1 is the standard of care in Japan in postoperative adjuvant chemotherapy for stage III gastric cancer, but long-term survival and the number of DS cycles required are unclear. The purpose of this study was to investigate the impact of the number of cycles of DS therapy on the 5-year survival in stage III gastric cancer in a pooled analysis of two phase II trials (OGSG0604 and OGSG1002). Patients and methods Patients with histologically confirmed stage III gastric cancer who underwent gastrectomy with D2 lymphadenectomy were enrolled in this pooled analysis. They received DS therapy for four or eight cycles, followed by S-1 until 1 year postgastrectomy. The 5-year overall survival (OS) and the 5-year disease free survival (DFS) by the landmark analysis was evaluated. Results In total, 113 patients from the OGSG0604 and OGSG1002 trials were enrolled in this study. The landmark analysis showed a 5-year OS that was better with four to eight cycles of DS therapy than with one to three cycles of DS therapy, with the best 5-year OS of 77.4% (95% confidence interval, 66.5–90.1%) for eight cycles. The 5-year DFS was approximately 66% when four or eight cycles of DS therapy were given. Conclusion Although eight cycles of DS therapy may prolong prognosis, the present study did not provide a clear conclusion as to how many DS therapy cycles are needed to improve prognosis after D2 gastrectomy for stage III gastric cancer. Trial registration Registration number: UMIN00000714 and UMIN000004440.