Metastasis to the stomach: a systematic review [version 1; peer review: 2 approved]

Background: This study reviews the literature on gastric metastases (GM) in terms of diagnosis, treatment, and outcomes. The goal of this study was to provide clinicians with a reliable and beneficial source to understand gastric metastases arising from various primary tumors and to present the growing literature in an easily accessible form. Methods: Articles published in English language from implementation of MEDLINE and Cochrane databases until May 2022 were considered for the systematic review. Articles other than English language, letters to the editor, posters, and clinical images were excluded. Hematogenous and lymphogenic metastases were included whereas direct tumoral invasion and seeding were excluded. Articles and abstracts were analyzed and last selection was done after cross-referencing and by use of defined eligibility criteria. Results: In total 1,521 publications were identified and 170 articles were finally included totaling 186 patients with GM. The median age of patients was 62 years. Gynecologic cancer was the most common cancer type causing GM (67 patients), followed by lung cancer (33 patients), renal cancer (20 patients), and melanoma (19 patients). One of the main treatment methods performed for metastasis was resection surgery (n=62), sometimes combined with chemotherapy (ChT) or immunotherapy. ChT was the other most used treatment method (n=78). Also, immunotherapy was amongst the most preferred treatment options after surgery and ChT (n=10). Conclusions: As 172 case reports were screened in the systematic review from different journals, heterogeneity was inevitable. Some articles missed important information such as complete follow-up or clinical information. Moreover, since all of the included articles were case reports quality assessment could not be performed. Among 172 case reports reviewed, resection surgery was performed the most and was sometimes combined with ChT and immunotherapy. Further research about what type of treatment has the best outcomes for patients with gastric metastases is needed.