Incidence and the high-risk factors of intracranial metastases in the perhippocampus region in 345 patients with lung cancer

Objective: To investigate the incidence of and high-risk factors for hippocampal metastasis (HM) in patients with brain metastases of lung cancer, to determine the safety of hippocampus-sparing whole brain radiotherapy (HS-WBRT), and to find out patients eligible for HS-WBRT. Methods: A retrospective study was performed on clinical data from 345 patients with brain metastases of lung cancer who were admitted to our hospital from 2011 to 2014. The hippocampus plus a 5-mm margin was delineated. Univariate and multivariate logistic analyses were used to identify high-risk factors for hippocampal metastasis. The Cox model was used for multivariate prognostic analysis. Results: In the 345 patients, there were 1621 intracranial metastatic lesions. Sixteen (4.6%) of the 345 patients and 16(0.99%) of the 1621 intracranial metastatic lesions had hippocampal metastasis; 42(12.2%) of the 345 patients and 45(2.78%) of the 1621 intracranial metastatic lesions had metastasis in the hippocampus plus a 5-mm margin. The univariate and multivariate logistic analyses showed that the number of brain metastases was correlated with hippocampal metastasis (HR = 1.14, P = 0.000). In the 139 patients with intracranial progression after treatment, 17 (12.2%) had hippocampal metastasis recurrence. The Cox prognostic analysis showed that tumor stage and genetic information were related to the overall survival in patients with brain metastases. Conclusions: The number of brain metastases is a high-risk factor for hippocampal metastasis. The lung cancer patients with more brain metastases have a higher incidence of hippocampal metastasis. HS-WBRT is recommended for lung cancer patients with fewer brain metastases, early-stage disease, and genetic mutations or rearrangement. (authors)