Targeting CNS Metastases in Non-Small Cell Lung Cancer With Evolving Approaches Using Molecular Markers: A Review

Importance: Central nervous system (CNS) metastases presenting as either brain parenchymal metastases or leptomeningeal metastases are diagnosed in up to 50% of patients with advanced non-small cell lung cancer during their disease course. While historically associated with a poor prognosis due to limited treatment options, the availability of an increasing number of targeted therapies with good CNS penetration has significantly improved clinical outcomes for these patients. This has occurred in parallel with a more nuanced understanding of prognostic factors. Observations: Multiple clinical trials have reported that disease control can be observed with targeted therapies with adequate CNS penetration, particularly for patients with molecular alterations in EGFR, ALK, ROS1, and RET. For these tumors, systemic targeted therapy may be used first for the management of CNS metastases, prior to considering radiation therapy (RT). At the time of isolated progression in the CNS, RT may be considered for the progressing lesions with continuation of the same systemic therapy. For other molecular alterations as well as for patients treated with checkpoint inhibitors, data are not yet clear if systemic therapy is sufficient for untreated CNS metastases, and early RT may need to be integrated into the treatment planning. An increasing number of studies investigate the role that emerging techniques, such as the sequencing of tumor DNA from resected brain metastases tissue or cerebrospinal fluid or radiomics-based analysis of CNS imaging, can play in guiding treatment approaches. Conclusions and Relevance: With multiple generations of targeted therapies now available, the treatment for CNS metastases should be tailored to the patients with consideration given to molecular testing results, CNS penetrance of systemic therapy, patient characteristics, and multidisciplinary review. More research is needed in understanding the clonal evolution of CNS metastases, and the development of novel therapeutics with CNS efficacy.