We appreciate the interest of Drs. Spiliotis and Zoras [1] in our article and their knowledge and faith in ACT-GC, the Japanese randomized trial that explored S-1 as a postoperative adjuvant chemotherapy for gastric cancer [2], despite the fact that the drug is unavailable in Europe. Their remark that a definitive conclusion about the efficacy of S-1 monotherapy for CEA mRNA-positive patients cannot be reached from such a small-scale study is quite a relevant observation. Actually, in clinical practice, we treat stage II/III gastric cancer patients using S-1 monotherapy regardless of the CEA mRNA status. Our study was started when the ACTS-GC was still ongoing. Phase III trials for postoperative chemotherapy had a long history of negative studies in Japan [3, 4] and elsewhere. Reasons for these failures could be the lack of effective cytotoxic agents, inclusion of an excessive number of patients who had no residual disease and therefore had been cured by surgery [3], and insufficient power in the trial design [4]. One reason for our conducting the RT-PCR trial was to find the potential danger of the ACTS-GC failing to show a benefit of adjuvant chemotherapy and join the long list of negative trials. Since RT-PCR could identify patients with residual disease with more sensitivity than the conventional staging scheme, our intention in that event was to urge our colleagues to perform RT-PCR for all stage II/III patients and prescribe S-1 for the CEA mRNA (?) population. ATCS-GC turned out to be a success while our phase II failed to prove our hypothesis. Ironically, our study demonstrated that the rate of peritoneal relapse among CEA mRNA-positive patients is much higher than in the ACTS-GC study. The main relevance of our article is that detection of CEA mRNA remains useful for identifying patients at high risk of peritoneal relapse at a time when S-1 therapy has become standard. The opinion of Spiliotis and Zoras that the combination of radiotherapy with S-1 as the next crucial step does not apply in Japan where local control has been achieved by lymph node dissection [2, 5]. The efficacy of trastuzumab for treating unresectable gastric cancer has been confirmed by the ToGA trial [6] and its use as an adjuvant therapy appears promising. However, lessons learned from colorectal cancer do not guarantee that molecular targeting agents that are effective in the advanced setting will function similarly in the adjuvant setting. In addition, the rate of HER2 positivity is about 20% in stomach cancer and is higher in intestinal-type cancer than in diffuse-type cancer, which commonly disseminates intraperitoneally [6]. Therefore, trastuzumab might not contribute greatly to the prevention of peritoneal dissemination. Peritoneal carcinomatosis represents the most common route of tumor dissemination in gastric cancer patients and the prevention of peritoneal carcinomatosis is a crucial part of the therapeutic strategy. There is a promising treatment option of intraperitoneal chemotherapy that will soon develop into a clinical trial [7]. At the same time, intraperitoneal chemotherapy is a technically demanding procedure compared to systemic chemotherapy, given the need for catheter placement and management of particular kinds of adverse events. Thus, we hope that our genetic detection of peritoneal micrometastasis will prove helpful in facilitating the proper selection of patients who are likely to benefit from intraperitoneal chemotherapy. S. Ito (&) Department of Gastroenterological Surgery, Aichi Cancer Center, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan e-mail: seito@aichi-cc.jp