Prognosis-predicting factor of gastrectomy after systemic cancer therapy for cStage IVB gastric cancer.

BACKGROUND: The clinical role of gastrectomy after systemic cancer therapy for cStage IVB gastric cancer (GC) remains controversial. This single-center study evaluated the clinical outcomes of gastrectomy after systemic cancer therapy in cStage IVB GC to identify prognosis-predicting factors. METHODS: We retrospectively reviewed patients with cStage IVB GC who received systemic cancer therapy as initial treatment from 2013 to 2023 and subsequently underwent gastrectomy. Patients were categorized as having oligometastatic disease or polymetastatic disease based on pre-treatment disease status. Survival outcomes and prognostic factors were analyzed. RESULTS: Among 1,591 patients who received systemic cancer therapy, 121 (7.6%) underwent gastrectomy (79 oligometastatic disease and 42 polymetastatic disease). The 3-year overall survival (OS) rate was 65% for the entire cohort. Patients with oligometastatic disease had better survival than those with polymetastatic disease (3-year OS: 76% vs. 43%, p = 0.009). Major pathological response (MPR) was observed in 39 patients (32%) and was associated with favorable survival in both oligometastatic (3-year OS: 97%) and polymetastatic disease (3-year OS: 89%). Further stratification showed similarly favorable survival in patients with clinical complete response and those without clinical complete response but with MPR, whereas patients without either response had poor outcomes (3-year OS: 94%, 95%, and 50%, respectively; p < 0.001). CONCLUSIONS: Postoperative prognosis after gastrectomy for cStage IVB GC appears to depend largely on pretreatment metastatic status and extent of response to systemic therapy. Technical resectability alone may be insufficient for surgical decision-making, particularly in polymetastatic disease.