MET-08 Air in cistern or ventricle after brain metastasis surgery is a predictor of early postoperative intracranial recurrence

INTRODUCTION: The operations of brain metastasis are on the increase as a result of more routine diagnostic imaging and improved extracranial systemic treatment strategies. Opening of the cistern or ventricle during tumor resection may promote local recurrence and cerebrospinal fluid dissemination. We investigated whether the air found in the cistern/ventricle on postoperative Computed tomography (CT) was a predictor of postoperative recurrence. METHODS: Between 2012 and 2019, 27 patients with single brain metastasis were treated with gross total resection at our hospital. The patients in which air was found in the cistern or ventricle of the head CT on the day after surgery was designated as air(+) group, and the patients without air was designated as air(-) group. The primary outcome was the local recurrence, as diagnosed with neuroimaging. The death due to other than brain metastasis was defined as competing risk. RESULTS: CT air(+) group was 17 patients, whereas CT air(-) group was 10 patients. There was no significant difference between the two groups, such as age and sex. Estimated 1-year brain tumor recurrence rate was 70% in the air(+) group and 5.9% in the air(-) group. (p = 0.004). On the other hand, no significant difference was observed in estimated 1-year competing risk between in the air(+) group (10%) and in the air(-) group (2.4%). CONCLUSION: En bloc resection of brain metastasis is effective, but there was no report on the risk of opening the cistern or ventricle. Our results indicate that postoperative air presence in the cistern or ventricle could be a predictor of early postoperative recurrence. In metastatic brain tumor removal, the cistern and ventricle should not be opened, and close follow-up should be done if air in the cistern or ventricle is detected on postoperative CT.