Conversion therapy for peritoneal lavage cytology-positive type 4 and large type 3 gastric cancer patients selected as candidates for R0 resection by diagnostic staging laparoscopy

Background The long-term outcomes of type 4 and large type 3 gastric cancer patients with positive peritoneal lavage cytology (CY1) remain unsatisfying. We evaluated our treatment strategy of conversion therapy for CY1 patients without peritoneal dissemination (P0). Methods Diagnostic staging laparoscopy (DSL) was performed before treatment. Chemotherapy was applied for DSL-diagnosed P0CY1. The re-evaluation of peritoneal metastasis by staging laparoscopy (re-SL) was performed when a response to chemotherapy was identified by gastroscopy and/or CT. Gastrectomy with radical lymphadenectomy was applied as conversion therapy when peritoneal lavage cytology-negative (CY0) and PO were diagnosed with re-SL, with the aim of achieving RO resection. Chemotherapy was continued as palliative treatment in patients for whom re-SL was not applicable or when re-SL did not confirm P0CY0. The long-term outcomes were retrospectively evaluated. Results Between 2009 and 2015, 214 patients with type 4 and large type 3 gastric cancer underwent DSL in the Cancer Institute Hospital. Thirty-nine patients were initially diagnosed with POCY1. Seven patients received palliative gastrectomy first due to outlet obstruction or other reasons. Thirty-two patients received chemotherapy first. Among them, 13 patients underwent gastrectomy as conversion therapy and 19 were treated with palliative chemotherapy. The 3-year survival rate of patients who underwent conversion therapy, palliative chemotherapy and palliative gastrectomy was 76.9% [95% confidence interval (CI) 47.8-92.4%], 10.5% (95% CI 1.9-42.3%), and 0%, respectively. Conclusion Conversion therapy might be a promising treatment for POCY1 type 4 and large type 3 gastric cancer patients. Re-SL was useful for selecting candidates for RO resection.