SURG-22. BRAIN METASTASIS FROM ADVANCED GASTRIC CANCERS: HIGH INCIDENCE OF LEPTOMENINGEAL DISSEMINATION AND ITS CLINICAL IMPACT ON SURVIVAL

Abstract OBJECTIVE Advanced gastric cancer is one of the most common and fatal cancers worldwide, and due to its highest incidence rate in Eastern Asian, it is steadily considered important. However, brain metastasis from advanced gastric cancer is very rare, and its incidence is reported as less than 1% of patients with primary advanced gastric cancer. There have been very few studies describing on the incidence and clinical outcome of patients with brain metastasis from advanced gastric cancers. METHOD We retrospectively analyzed 128 patients diagnosed as brain metastasis from advanced gastric cancers, and then underwent treatment from 2005 to 2021 April in our institution. Patients’ survival and its associated prognostic factors were evaluated. Especially, subgroup analysis on patients with leptomeningeal dissemination (LMD) was performed. RESULT Of total 128 patients of advanced gastric cancer with brain metastasis, 74 patients (58%) were diagnosed with LMD. Overall survival of LMD group was significantly shorter than that of non-LMD group (p<0.001). Patients treated with tumor removal (TR) followed by whole brain radiotherapy (WBRT) showed superior overall survival than patients with WBRT alone (p=0.002). Among 74 LMD patients, those who underwent WBRT combined with intrathecal methotrexate (IT MTX) showed better outcome than patients with WBRT alone (p=0.025). Specifically, for the 51 pure LMD patients without parenchymal brain metastasis, the superiority of adjuvant IT TMX on survival outcome was more apparent (p=0.011). CONCLUSION The incidence of LMD has been underestimated as 58% of patient with brain metastasis from advanced gastric cancers presented LMD on radiological and cytological studies. If the brain tumor is surgically resectable, TR followed by WBRT can be the first choice of treatment provides survival benefit. Patients with LMD are most benefited from IT MTX combined with WBRT.