Early detection of brain metastases and appropriate local therapy followed by systemic chemotherapy may improve the prognosis of gastric cancer.

Brain metastases develop in 0.5-0.7% of patients with gastric/gastroesophageal junction (G/GEJ) cancer. Although rare, brain metastasis is often identified when the patient is already symptomatic; hence prognosis is poor. Given the therapeutic developments for G/GEJ cancer, overall survival is prolonged, thereby the incidence of brain metastases is predicted to increase. We retrospectively surveyed the rate of brain metastasis among 1257 patients diagnosed with G/GEJ cancer who received chemotherapy between January 2011 and April 2021. We investigated the time of onset of brain metastasis, treatments administered, and impact of the metastasis on the overall treatment course and prognosis. Of the 741 patients included in the analysis, brain metastasis was confirmed in 16 (2.2%). The median survival time (MST) from G/GEJ cancer diagnosis was 14.9 months in patients with brain metastasis detected during the treatment period, and the MST from the diagnosis of brain metastasis was 2.8 months. Patients who received chemotherapy exhibited prolonged survival compared with those who did not (12.4 months vs 1.0 months, p < 0.001). Our findings suggest that the early detection of brain metastases and local therapy for poor responders to chemotherapy enable the continuation of chemotherapy and prolong survival.