Lymph Node Size Predicts for Asymptomatic Brain Metastases in Patients With Non–small‐cell Lung Cancer at Diagnosis

Abstract

Background: We questioned whether the National Comprehensive Cancer Network recommendations for brain magnetic resonance imaging (MRI) for patients with stage ≥ IB non–small‐cell lung cancer (NSCLC) was high‐yield compared with American College of Clinical Pharmacy and National Institute for Health and Care Excellence guidelines recommending stage III and above NSCLC. We present the prevalence and factors predictive of asymptomatic brain metastases at diagnosis in patients with NSCLC without extracranial metastases. Materials and Methods: A retrospective analysis of 193 consecutive, treatment‐naïve patients with NSCLC diagnosed between January 2010 and August 2015 was performed. Exclusion criteria included no brain MRI staging, symptomatic brain metastases, or stage IV based on extracranial disease. Univariate and multivariate logistic regression was performed. Results: The patient characteristics include median age of 65 years (range, 36‐90 years), 51% adenocarcinoma/36% squamous carcinoma, and pre‐MRI stage grouping of 31% I, 22% II, 34% IIIA, and 13% IIIB. The overall prevalence of brain metastases was 5.7% (n = 11). One (2.4%) stage IA and 1 (5.6%) stage IB patient had asymptomatic brain metastases at diagnosis, both were adenocarcinomas. On univariate analysis, increasing lymph nodal stage (P = .02), lymph nodal size > 2 cm (P = .009), multi‐lymph nodal N1/N2 station involvement (P = .027), and overall stage (P = .005) were associated with asymptomatic brain metastases. On multivariate analysis, increasing lymph nodal size remained significant (odds ratio, 1.545; P = .009). Conclusion: Our series shows a 5.7% rate of asymptomatic brain metastasis for patients with stage I to III NSCLC. Increasing lymph nodal size was the only predictor of asymptomatic brain metastases, suggesting over‐utilization of MRI in early‐stage disease, especially in lymph node‐negative patients with NSCLC. Future efforts will explore the utility of baseline MRI in lymph node‐positive stage II and all stage IIIA patients.