Conversion Surgery in Metastatic Gastric Cancer and Cancer Dormancy as a Prognostic Biomarker.

The role of conversion surgery in metastatic gastric cancer remains unclear. Cancer dormancy markers might have a role in predicting the survival in patients with conversion surgery. We identified 26 patients who went through conversion surgery, i.e., a curative-intent gastrectomy with metastasectomy after chemotherapy in initially metastatic gastric cancer. As controls, 114 potential candidates for conversion surgery who only received chemotherapy were included for the propensity score matching. Conversion surgery showed a significantly longer overall survival (OS) compared with only palliative chemotherapy (median-43.6 vs. 14.0 months, respectively, p < 0.001). This better survival in the conversion surgery group persisted even after propensity matching (p < 0.001), and also when compared to patients with tumor response over 5.1 months in the chemotherapy only group (p = 0.005). In the conversion surgery group, OS was longer in patients with R0 resection (22/26, 84.6%) than without R0 resection (4/26, 15.4%) (median-not reached vs 22.1 months, respectively, p = 0.005). Although it should be interpreted with caution due to the primitive analysis in a small population, the positive expression of NR2F1 showed a longer duration of disease-free survival (DFS) after conversion surgery (p = 0.016). In conclusion, conversion surgery showed a durable OS even in patients with initially metastatic gastric cancer when R0 resection was achieved after chemotherapy.