Decision in Context: A Practical Framework for Sequencing Systemic and CNS Therapies in Brain Metastases

Decision in Context: A Practical Framework for Sequencing Systemic and CNS Therapies for Brain Metastases

The management of brain metastases has undergone a fundamental shift over the past decade. Historically, central nervous system (CNS) involvement necessitated local therapies such as whole-brain radiation therapy (WBRT), stereotactic radiosurgery (SRS), or neurosurgical intervention, with systemic therapies playing a limited role due to poor blood-brain barrier penetration among other factors such as the unique CNS microenvironment. However, the emergence of modern targeted therapies and antibody-drug conjugates (ADCs) with demonstrated intracranial activity has expanded treatment options while introducing new complexity in sequencing decisions.^1,2

Clinicians are now tasked with integrating systemic and CNS-directed therapies in a way that accounts for disease biology, symptom burden, prior treatments, and evolving evidence. This article presents a practical framework to guide decision-making in this increasingly nuanced landscape.

Applying Evidence to Systemic Therapy Selection in CNS Disease

Emerging Evidence for Intracranial Activity of Systemic Therapies
Recent advances in systemic therapy have challenged the historical assumption that CNS disease must be managed primarily with local interventions. In non-small cell lung cancer (NSCLC), next-generation tyrosine kinase inhibitors (TKIs), such as osimertinib for EGFR-mutated disease, and ADCs, such as trastuzumab deruxtecan (T-DXd) for HER2-mutated disease, have demonstrated high intracranial response rates and durable CNS control.^3,4 These agents achieve therapeutic CNS penetration and are now considered foundational in managing brain metastases in molecularly defined subsets.

In breast cancer, HER2-directed therapies have similarly advanced CNS management. Tucatinib combined with trastuzumab and capecitabine, as well as trastuzumab deruxtecan (T-DXd), have shown clinically meaningful intracranial activity in brain metastases.^5,6 These data have expanded the role of systemic therapy beyond extracranial disease control and into the CNS therapeutic space.

Interpreting CNS Efficacy in Clinical Context
While intracranial response rates are increasingly reported in clinical trials, their interpretation requires careful contextualization. Clinical trial populations often differ from real-world patients in terms of symptom burden, prior CNS-directed therapy, and lesion characteristics. These factors can influence outcomes and should be considered when applying trial data to individual patients.^1,2

Sequencing Systemic and CNS-Directed Therapies

Prioritizing Systemic Therapy vs Local CNS Intervention
One of the most critical decisions in managing brain metastases is determining whether to prioritize systemic therapy or local CNS-directed treatment. This decision hinges on symptom burden, lesion characteristics, and the availability of effective systemic options.

For patients with asymptomatic or minimally symptomatic brain metastases, low CNS disease burden, and access to CNS-active systemic therapy, initiating systemic treatment is appropriate. This approach can provide simultaneous control of intracranial and extracranial disease while avoiding the neurocognitive risks associated with radiation.^1,2

Conversely, patients with symptomatic lesions, high CNS disease burden, or no access to CNS-active systemic therapy often require immediate local therapy, such as WBRT, SRS, or surgical resection, to stabilize neurologic function before transitioning to systemic treatment.

This framework emphasizes that sequencing decisions are dynamic rather than binary and require continuous reassessment and multidisciplinary input.

Balancing Intracranial and Systemic Disease Control
Optimal sequencing requires balancing intracranial control with systemic disease management. In many cases, systemic therapy can address both compartments, but discordance between CNS and extracranial disease status and molecular profiles remains a challenge.

For example, widespread progression in both compartments may necessitate a change in systemic therapy, ideally to an agent with demonstrated CNS activity. The availability of such agents has made it increasingly feasible to align intracranial and systemic treatment goals.

In contrast, a patient with controlled systemic disease but isolated CNS progression may benefit from local therapy while continuing the same systemic regimen. This approach preserves systemic disease control while addressing CNS-specific progression.^1,2

Navigating Competing Treatment Goals in Evolving Guidelines
Despite rapid advances, guidance on sequencing systemic and CNS therapies remains heterogeneous and, in some cases, nonspecific. Recent CNS-focused guidelines emphasize individualized decision-making based on clinical context, highlighting the importance of multidisciplinary input.^7,8

Clinicians must often navigate competing priorities, including rapid symptom control, long-term neurocognitive preservation, systemic disease control, and patient quality of life. In this setting, shared decision-making and careful communication are essential to align treatment strategies with patient goals.

Multidisciplinary Coordination and CNS Toxicity Management

The Central Role of Multidisciplinary Care
The increasing complexity of CNS management has elevated the importance of multidisciplinary care. Optimal outcomes depend on coordinated input from medical oncology, radiation oncology, neurosurgery, neuro-oncology, neuroradiology, and supportive care teams.^7,8

Multidisciplinary tumor boards or dedicated brain metastases clinics facilitate real-time decision-making, improve care coordination, and enable timely access to clinical trials. This approach is particularly valuable in navigating evolving treatment paradigms and aligning care with patient goals.

Monitoring and Managing CNS Symptoms
Patients receiving systemic therapy for CNS disease require careful monitoring for neurologic symptoms, including headache, cognitive changes, seizures, and focal deficits. Prompt evaluation with neuroimaging is essential to distinguish between disease progression and treatment-related effects.^7,8

Supportive care plays a critical role. Corticosteroids are reserved for symptomatic edema and should be tapered as quickly as possible. Antiepileptic therapy is used when seizures occur, with levetiracetam commonly preferred due to its favorable safety profile and minimal drug interactions.

Differentiating Treatment Effects From Disease Progression
One of the more challenging aspects of CNS management is distinguishing treatment-related effects, such as radionecrosis, from true disease progression. Radiographic changes following radiation can mimic tumor growth, leading to potential misinterpretation and inappropriate treatment changes.^7,8

Advanced imaging techniques, including perfusion MRI and PET imaging, as well as multidisciplinary review, can aid in differentiation. In some cases, biopsy may be required for definitive tissue diagnosis.

It is critical to avoid premature discontinuation of effective systemic therapy, particularly when extracranial disease remains controlled. A cautious, evidence-based approach to interpreting CNS imaging findings is therefore essential.

Integrating Evidence Into Clinical Practice

The management of brain metastases has evolved from a predominantly local treatment paradigm to a more integrated, biology-driven approach. CNS-active systemic therapies now play a central role, particularly in molecularly defined subsets of breast and lung cancer.

However, this progress has introduced new complexity. Sequencing decisions must balance intracranial control, systemic disease management, toxicity considerations, and patient preferences. A structured, multidisciplinary framework is essential to effectively navigate these competing priorities.

Screening strategies remain nuanced, particularly in breast cancer, where routine screening for asymptomatic patients is not yet standard but may evolve with emerging data. In contrast, brain imaging is routinely recommended in advanced NSCLC and should be promptly performed in any patient with new neurologic symptoms.

Ultimately, optimal care requires continuous reassessment, integration of emerging evidence, collaboration across disciplines, and consideration of patients’ goals. As systemic therapies continue to improve and clinical trials further define CNS-specific outcomes, the ability to personalize sequencing strategies will continue to advance, with the goal of improving both survival and quality of life for patients with brain metastases.

References:

1. Jerzak KJ, Leighl NB, Sahgal A, et al. Systemic therapy for brain metastases: a changing landscape. Lancet Oncol. 2025;26(11):1398-1400.
2. Porte M, Massard C. New therapies for brain metastases: an update. Curr Opin Oncol. 2025;37(6):611-617.
3. Soria JC, Ohe Y, Vansteenkiste J, et al. Osimertinib in untreated EGFR-mutated advanced non–small-cell lung cancer. N Engl J Med. 2018;378(2):113-125.
4. Jänne PA, Planchard D, Goto K, et al. Trastuzumab deruxtecan for ERBB2-mutant metastatic non-small cell lung cancer with or without brain metastases: a secondary analysis of randomized clinical trials. JAMA Netw Open. 2025;8(11):e2543107.
5. Murthy RK, Loi S, Okines A, et al. Tucatinib, trastuzumab, and capecitabine for HER2-positive metastatic breast cancer. N Engl J Med. 2020;382(7):597-609.
6. Harbeck N, Ciruelos E, Jerusalem G, et al; DESTINY-Breast12 study group. Trastuzumab deruxtecan in HER2-positive advanced breast cancer with or without brain metastases: a phase 3b/4 trial. Nat Med. 2024;30(12):3717-3727.
7. Vogelbaum MA, Brown PD, Messersmith H, et al. Treatment for brain metastases: ASCO-SNO-ASTRO guideline. J Clin Oncol. 2022;40(5):492-516.
8. Nabors LB, Portnow J, Baehring J, et al. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for Central Nervous System Cancers (Version 1.2026). © 2026 National Comprehensive Cancer Network, Inc. To view the most recent and complete version of the NCCN Guidelines®, go online to NCCN.org.