Heterogeneity and prognosis of single organ metastases in gastric cancer.

Background: While single organ metastases generally present a more optimistic prognosis compared to multiple metastases, the influence of the specific organ site for single organ metastases on prognosis remains undetermined. This retrospective study aimed to investigate the prognostic differences in late-stage gastric cancer with single organ metastasis.

Methods: Data for patients diagnosed with gastric cancer were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database for survival analysis, covering years spanning from 2010 to 2016. Furthermore, Kaplan-Meier survival curves and Cox regression were utilized to analyze overall survival (OS) and disease-specific survival (DSS). Additionally, given the impact of confounders and bias on the results, prognosis was further analyzed using propensity score matching (PSM) and floating absolute risk methods.

Results: A cohort comprising 4,297 patients diagnosed with gastric cancer and exhibiting single organ metastasis was hereby enrolled. Liver metastasis was the most common (71% of the total), while brain metastasis accounted for the least (1.7% of the total). Compared to other metastases, patients with bone metastasis presented the worst OS [hazard ratio (HR), 1.319; 95% confidence interval (CI): 1.207-1.442; P<0.001], and this remained consistent even upon the application of floating absolute risk (HR, 1.10; 95% CI: 1.01-1.20) and PSM methods (HR, 1.187; 95% CI: 1.053-1.339; P=0.005). In addition, subgroup analysis and interaction tests of OS revealed an interaction between age (P=0.02), histological type (P=0.002), and bone metastasis.

Conclusions: In patients with single organ metastasis of gastric cancer, the prognosis varies by the metastatic site, with bone metastasis presenting the poorest outcome. Overall, this study forges a foundation for further research on the mechanisms and patterns of different metastatic sites in gastric cancer and informs treatment strategies.