Comparison of clinical and MRI features of brain metastases between ALK+ and ALK- NSCLC.

Background: Non-small-cell lung cancer (NSCLC) is the primary cause of brain metastases (BM). This study aimed to investigate differences in clinical and magnetic resonance imaging (MRI) features of BM between anaplastic lymphoma kinase (ALK) gene fusion (ALK+) and ALK wild-type (ALK-) NSCLC, and to preliminarily assess the efficacy of radiotherapy for treating BM.

Methods: A retrospective analysis included 101 epidermal growth factor receptor (EGFR)- NSCLC patients with BM: 41 with ALK gene fusion and 60 being ALK-. The brain MRI and clinical features were compared between different ALK status using the multivariate analysis, and a nomogram was constructed to predict ALK gene fusion. Fifty-six patients who did not undergo cerebral surgery and had complete pre- and post- treatment data were further divided based on whether they received radiotherapy. Log-rank test was used to compare the short-term effect of treatment between the two groups under different genotypes.

Results: ALK+ BM exhibited decreased peritumoral brain edema size, lower peritumoral brain edema index (PBEI), and a more homogeneous contrast enhancement pattern compared to ALK- BM. Age (OR = 1.04; 95%CI: 1.02-1.06), time to BM (OR = 1.50; 95% CI: 1.04-2.14), PBEI (OR = 1.26; 95% CI: 0.97-1.62), smoking status (smoking index >400 vs. non-smoking status: OR = 1.42; 95% CI: 0.99-2.04) and contrast enhancement pattern (OR = 1.89; 95% CI: 1.28-2.78) were associated with ALK gene fusion. A nomogram based on these variables demonstrated acceptable predictive efficiency (AUC = 0.844). In the ALK+ group, patients who received radiotherapy did not show increased disease control rate (DCR) or progression-free survival (PFS). In contrast, in the ALK- group, those who received radiotherapy had improved objective response rate (ORR), DCR, and PFS compared to those who were only treated with systemic therapy.

Conclusions: The clinical and MRI features of BM can indicate the status of ALK in NSCLC. In the ALK- group, patients who received radiotherapy showed higher ORR, DCR, and PFS compared to those who did not.