Radiographic Features of Metastatic Brain Tumors from ALK-rearranged Non-small Cell Lung Cancer: Implications for Optimal Treatment Modalities

Purpose: To investigate the radiological features on magnetic resonance imaging (MRI) of brain metastases (BM) from ALK-rearranged non-small cell lung cancer (NSCLC). Patients and Methods: We retrospectively evaluated data from 40 eligible patients with ALK-rearranged NSCLC. Radiographic features of metastatic brain tumors, including the number, size, location, and peritumoral brain edema size (PBES), were delineated using MRI. Results: 13 patients had metachronous BM (MBM), having developed BM at least 6 months after diagnosis with NSCLC. The remaining patients were categorized as having synchronous BM (SBM). Compared with patients in the SBM group, patients in the MBM group were found to have more favorable values for radiological features including BM number, BM size, and PBES. Ten (76.9%) of the 13 patients with MBM had ≤3 lesions and were asymptomatic, and none had developed a diffuse BM pattern, supporting the adoption of stereotactic radiosurgery (SRS) in the majority of these patients and against the administration of prophylactic cranial irradiation (PCI). Conversely, among the 27 patients with SBM, 15 (55.6%) patients had >3 lesions and 12 (44.4%) patients were symptomatic, highlighting the necessity of rapidly administrating brain radiotherapy, either as SRS or whole brain radiotherapy (WBRT). Importantly, only two patients (5.0%) had metastases in the hippocampus and peri-hippocampus region, and both were in the SBM group, indicating the feasibility of hippocampal avoidance WBRT in ALK-rearranged NSCLC. Conclusions: Both WBRT and SRS are appropriate for the treatment of BM in patients with ALK-rearranged NSCLC. The incidence of BM in the hippocampus and peri-hippocampus region is low in our radiological data. Nearly 80% of patients with metachronous BM have oligo-metastatic lesions, indicating that SRS is the preferred therapy while PCI is not indicated.