ObjectiveTo analyze the clinicopathological characteristics and prognostic factors in gastric cancer patients with bone metastasis, and to evaluate the impact of different treatment regimens on survival in patients with synchronous and metachronous bone metastasis.MethodsA total of 120 gastric cancer patients with bone metastasis treated at Nanjing Drum Tower Hospital between 2015 and 2023 were enrolled, including 36 with synchronous bone metastasis and 84 with metachronous bone metastasis. Clinicopathological features were compared between the two groups using the χ² test. Cox proportional hazards regression model was employed to identify risk factors for overall survival after bone metastasis (OS-BM). The Kaplan-Meier method was used to analyze the effects of different treatments on OS-BM in both synchronous and metachronous groups.ResultsAmong the 120 patients, 104 (86.6%) had metastases to other organs. Comparative analysis revealed that synchronous bone metastasis patients exhibited elevated serum C-reactive protein and decreased serum albumin, whereas metachronous bone metastasis patients had reduced peripheral white blood cell and neutrophil counts (all P < 0.05). Metachronous bone metastasis (HR = 2.35, 95% CI [1.47, 3.74], P < 0.01), serum CA125 ≥ 30.2 U/mL (HR = 1.6,95% CI [1.03, 2.48], P = 0.036), white blood cell count ≥ 9.5 × 10⁹/L (HR = 2.15, 95% CI [1.17, 3.92], P = 0.013), and absence of immunotherapy (HR = 2.26, 95% CI [1.5, 3.39], P < 0.01) were independent risk factors affecting patient prognosis. Combined immunotherapy significantly prolonged OS-BM in gastric cancer patients with bone metastasis compared to non-immunotherapy regimens (9.63 vs 4.53 months, P = 0.002). Patients with metachronous bone metastasis demonstrated better response to immunotherapy compared to those with synchronous metastases (median OS-BM: 10.8 vs 7.3 months, P = 0.004).ConclusionImmunotherapy is an independent protective factor for survival in gastric cancer patients with bone metastasis. Early combination therapy centered on immunotherapy alongside chemotherapy is recommended to prolong survival in such patients.