MMAP-20 EFFECT OF SYSTEMIC THERAPY TIMING ON LOCAL RECURRENCE RISK FOLLOWING BRAIN METASTASIS RESECTION

Abstract Timing is an important consideration in the multimodal care planning for patients with brain metastasis. Insufficient time between administration of different modalities may result in an increased likelihood of treatment-related complications, while long time intervals may increase the risk of malignancy progression. Recent publications have focused on identifying the optimal time window between brain metastasis resection and radiotherapy. However, evidence on timing for systemic therapy following brain metastasis resection remains limited. This study aims to assess whether the time from brain metastasis resection to non-hormonal systemic therapy initiation is associated with local recurrence risk. We conducted a retrospective review of patients treated with brain metastasis resection, stereotactic radiosurgery (SRS), and non-hormonal systemic therapy at our institution. Time from surgery to non-hormonal systemic therapy administration was compared between recurrence and non-recurrence groups using Wilcoxon rank-sum test and Cohen’s d to estimate effect size. We identified 28 patients initiating SRS and non-hormonal systemic therapies within 120 days of brain metastasis resection. Across a median post-operative follow up time of 13.95 months, 5 of the 28 patients had a local recurrence at the site of the initially resected brain metastasis. The median time from surgery to non-hormonal systemic therapy was 51 days for patients without a recurrence versus 59 days for patients with a recurrence (p=0.17, d=-0.66). Karnofsky Performance Score at brain metastasis diagnosis (p=0.82), primary tumor histology (p=0.37), and extracranial disease status at brain metastasis diagnosis (p=0.62) were not significantly associated with local recurrence. Although no statistically significant difference was identified, the moderate estimated effect suggests that later initiation of non-hormonal systemic therapy may be associated with increased rates of local recurrence. The small sample size of this study limits statistical power, and larger studies are needed to fully understand this association and identify optimal post-operative systemic therapy timing.