Evaluation of Surveillance Strategies in Systemic Therapy for Brain Metastases

Overview

This retrospective study assessed surveillance imaging practices and outcomes in 33 patients treated with systemic therapy alone for brain metastases. Findings showed variable MRI monitoring intervals, common intracranial recurrences, and infrequent safety events, with many patients delaying radiation therapy for over one year.

Background

Brain metastases are a frequent complication of metastatic cancer, traditionally managed with local therapies such as whole brain radiation therapy or stereotactic radiosurgery. The advent of CNS-penetrating systemic therapies offers potential to control brain metastases without immediate local treatment, potentially reducing toxicity. However, evidence-based guidelines for surveillance during systemic therapy remain limited, and clinical practice varies. This study aimed to characterize real-world monitoring approaches and outcomes in patients receiving systemic therapy alone for brain metastases.

Data Highlights

Key Findings

• Only 14 of 33 patients received systemic therapy regimens supported by 2021 ASCO-SNO-ASTRO guidelines.
• Median intervals to first, second, and third surveillance MRIs were approximately 45, 95, and 180 days, respectively, with wide ranges.
• One-year cumulative incidence of local intracranial progression was similar between guideline and non-guideline groups (43% vs 32%, p=0.5).
• One-year cumulative incidence of subsequent brain radiation was not significantly different between groups (29% vs 44%, p=0.87).
• Neurological safety events during systemic therapy were infrequent, with only two patients experiencing seizures.
• Many patients were able to defer radiation therapy for over one year despite variable surveillance imaging frequency and common recurrences.

Clinical Implications

These findings suggest that systemic therapy alone for brain metastases can allow delay of radiation therapy in selected patients with manageable safety profiles. However, surveillance imaging intervals varied widely, highlighting the need for standardized, evidence-based monitoring protocols. Clinicians should carefully balance the risks of intracranial progression with the benefits of deferring radiation when using CNS-penetrating systemic therapies.

Conclusion

Systemic treatment of brain metastases without upfront radiation is increasingly utilized but lacks standardized surveillance guidelines. This study underscores the feasibility of this approach with infrequent adverse events and supports the development of evidence-based monitoring strategies.

References

1. ASCO-SNO-ASTRO Guidelines 2021 -- Brain Metastases Treatment Recommendations