[Clinical significance and efficacy of conversion surgery for patients with stage IV gastric cancer].

Gastric cancer is the second most common malignancy and the one of the leading causes of cancer-related death in China. In particular, the survival rate of patients with stage IV or unresectable gastric cancer is very poor. Conversion therapy for stage IV gastric cancer has been the main subject with much attention recently. It is defined to achieve an R0 surgical resection after chemotherapy for originally unresectable cancer due to technical and/or oncological reasons. However, the optimal indications for conversion surgery are still controversial, and how to select the most appropriate candidates for conversion therapy remains to be clarified. A new biological category for stage IV gastric cancer proposed by K Yoshida from Gifu University has been tested out in some trials, from which stage IV gastric cancer can be divided into two different classifications based on the absence (category 1: potentially resectable metastasis and category 2: marginally resectable metastasis) or presence (category 3:incurable and unresectable metastasis and category 4: non-curable metastasis) of macroscopic peritoneal dissemination. The optimal indications for conversion therapy mainly include the patients with category 2, and partially for patients with categories 3 and 4. A surgery-oriented classification proposed by Peking University Cancer Hospital tried to classify the stage IV gastric cancer for conversion therapy. It would be classified as resectable and unresectable categories, depending on uhether R0 resection is available by preoperative evaluation. In this classification, unresectable cancer can be further classified as conversed, partly conversed and non-conversed types based on extent of cancer metastasis. The resection of primary and metastatic lesion in unscreened stage IV gastric cancer was not testified to improve survival. REGATTA trial has identified no significant difference in survival rate between the chemotherapy only and palliative gastrectomy with postoperative chemotherapy for stage IV gastric cancer with a single non-curable factor. With development of conversion therapy, a consensus has been reached that the patients with unresectable gastric cancer initially exhibiting one non-curative factor, if having clinical response to chemotherapy, may obtain a survival benefit from subsequent R0 radical gastrectomy. Several novel combined chemotherapy regimens occasionally allow for conversion of an initially unresectable gastric cancer to resectable cancer in clinical practice. Conversion surgery may result in long-term survival in selected patients who respond to chemotherapy. Several previous studies have evaluated the positive prognostic role of surgery after chemotherapy in stage IV gastric cancer patients with one non-curative factor, such as peritoneal metastasis, para-aortic lymph node metastasis or liver metastasis. Gastric cancer is a highly heterogeneous tumor in nature, consisting of varying aggressive biological characteristics. Oncologically stage IV gastric cancer is a systemic disease, and the complete response to any therapy is really very rare, so that conversion therapy is a great clinical challenging problem for gastric cancer patients. Due to the multi-pathway metastasis, perioperative systemic chemotherapy is the most important in conversion therapy for stage IV gastric cancer, and a radical surgical resection is the key to improve prognosis. A good local control does not necessarily lead to prolonged survival in patients with stage IV gastric cancer, in which other sites metastases often emerge even after successful local-regional cancer-oriented treatment. To date, most reports of conversion therapy for gastric cancer were from single-center or retrospective study. If more reliable evidences are to be obtained, more multi-center and prospective RCT studies must be carried out.