Prognostic factors of conversion surgery for stage IV gastric cancer: A multi-institutional retrospective analysis.

Background: Conversion surgery (CS) is a highly anticipated strategy for stage IV advanced gastric cancer (AGC) with a good response to chemotherapy. However, prognostic factors limiting R0 resection remain unclear. In this multi-institutional study, we investigated the clinical outcomes of CS for stage IV AGC and the prognostic factors of CS-limiting R0 resection and analyzed them according to metastatic patterns. Methods: Clinical data on 210 patients who underwent CS for stage IV AGC at six institutions between 2007 and 2017 were retrospectively retrieved. The patient background, preoperative treatment, operative outcomes, and survival times were recorded. Prognostic factors for overall and recurrence-free survival were investigated using univariate and multivariate analyses for patients who underwent R0 resection. Results: R0 resection was achieved in 146 (70%) patients. The median survival time was 32 months, and the 3-year survival rate was 45%. Patients who achieved R0 resection had significantly longer survival than those with R1/2 resection (median survival time: 41.5 months vs. 20.7 months). Multivariate analysis identified pathological N positivity for overall and relapse-free survival and pathological T4 for relapse-free survival as significant independent poor prognostic factors of R0 resected patients. There was no significant difference in survival among the peritoneum, liver, and lymph node groups regarding the initial metastatic sites. Conclusions: CS with R0 resection for patients with stage IV AGC can lead to longer survival. Patients with pathological T4 and pathological N positivity were eligible for intensive adjuvant therapy after CS with R0 resection.