ESTRO 2025 - Abstract Book

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Clinical - CNS

ESTRO 2025

2. Tietze A, et al. Perfusion MRI derived indices of microvascular shunting and flow control correlate with tumor grade and outcome in patients with cerebral glioma. PLoS One. 2015 Apr 13; doi: 10.1371/journal.pone.0123044. 3.Sim Y, et al. Clinical, qualitative imaging biomarkers, and tumor oxygenation imaging biomarkers for differentiation of midline-located IDH wild-type glioblastomas and H3 K27-altered diffuse midline gliomas in adults. Eur J Radiol. 2024 Apr; doi: 10.1016/j.ejrad.2024.111384

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Digital Poster Differential Utilization and Spending for Conventional Radiotherapy vs. Stereotactic Radiosurgery for Brain Metastases Among Older Adults in the US Mabel Tang 1 , Jona A Hattangadi-Gluth 1 , Zachary R Moore 2 , Brandon S Imber 2 , Kathryn R Tringale 1 1 Radiation Medicine and Applied Sciences, UC San Diego, La Jolla, USA. 2 Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, USA Purpose/Objective: Although whole brain radiotherapy (WBRT) improves intracranial control of brain metastases, sparing normal brain tissue with stereotactic radiosurgery (SRS) achieves similar survival while reducing cognitive deterioration and often number of treatments. 1 However, SRS is expensive, requires stringent patient immobilization, and necessitates both technical and provider expertise. Treatment selection in older patients warrants nuanced decision-making considering goals of care, treatment tolerability, concern for neurotoxicity, and prognosis. Practice patterns in the US for this population are unclear. Material/Methods: Radiotherapy episodes from 2015-2019 were analyzed for US Medicare beneficiaries with brain metastases aged ≥65 years. Delivery technique (conventional vs. SRS), treatment year (2015-2019), age (65-74, 75-84, ≥85), site-of-care (freestanding vs. hospital-affiliated), and death within 90 days were covariables. Utilization of SRS vs. conventional was evaluated by multivariable logistic regression. Spending (Medicare-reimbursed professional and technical service fees over the 90-day episode in 2019 dollars) was evaluated with multivariable linear regression. Results: From 2015-2019, 33,258 episodes were included (21,524 [65%] SRS). SRS was used in 41% (4,135/1,013) of patients who died within 90 days and 66% (1,326/1,998) of patients ≥85 years. SRS utilization was associated with older age (age ≥85 vs. 65-74, odds ratio [OR] 1.4 [95%CI:1.3-1.6]) and hospital-affiliated sites (OR 2.3 [95%CI:2.2-2.5]); SRS use was less likely in patients who died within 90 days (OR 0.23 [95%CI:0.22-0.24]; p<0.01 for all). There was no interaction between site-of-care and death within 90 days. SRS use increased over time (OR 1.1 [95%CI:1.1-1.1]; p<0.01). SRS significantly increased spending (β=$6,512 [95%CI:6,421-6,602]) vs. conventional. The magnitude of increased spending with SRS vs. conventional was similar among patients who died within 90 days and for those who survived (mean differential $6,837 [p<0.001] and $6,840 [p<0.001], respectively). Conclusion: Hospital-affiliated centers were more likely to use SRS vs. conventional radiotherapy for older patients with brain metastases. While SRS use was less likely across both sites-of-care among patients with poor prognosis, its use was higher among patients ≥85 years, suggesting that providers may use age as opposed to prognosis as a guiding factor to choose SRS. SRS was increasingly used over time, possibly reflecting a widening patient population including those with more brain metastases. 2 How SRS use factors into the equipoise between WBRT vs. supportive care in frail patients requires further study. 3 SRS was associated with higher spending than conventional radiotherapy, thus financial alignment with value-based practice is critical. Future work is needed to refine the balance among intracranial control, patients’ treatment-related burden, and healthcare spending.