Systemic chemotherapy is the standard treatment in unresectable stage IV gastric cancer. However, for the intermittent extremely sensitive patients to the palliative chemotherapy, surgical treatment has been applied to prolong survival (conversion surgery). As few reports showed survival prolongation in selected patients in a retrospective analysis, a strong need for the consensus of indication to conversion surgery and validation of therapeutic efficacy of conversion surgery has been raised in Asia.

For the consensus generation, there are so many issues in patient selection criteria and treatment algorism. (1) Definition on unresectability is different surgeon to surgeon and institution to institution. It can be determined either image-based or surgery-based (laparoscopy or explo-laparotomy). Unresectability might be determined based on the loco-regional spread or systemic metastasis (intra-abdominal or extra-abdominal). (2) The exact surgical intervention time point is a big controversial issue. Surgery can be done after a fixed cycle of chemotherapy or at the maximum response period. And for the maximum response, sequential treatment with different chemotherapy regimens can be applied. (3) Definition of curative surgery is complicated in para-aortic lymph node metastasis case, peritoneal cytology positive case, and systemic metastasis case. (4) The criteria for the selection of adjuvant chemotherapy regimen and duration of the treatment is another issues. Most of the current reports showed survival prolongation of conversion surgery compared to the non-responsive patients to the first-line systemic chemotherapy. We do not know whether conversion surgery may have survival prolongation compared to the responders to the first-line treatment having subsequent chemotherapy with different regimens. The perspectives of KACO for these issues will be discussed.