Centre-specific treatment and outcomes of patients with brain metastases treated with whole brain or stereotactic radiation therapy: an Ontario-based retrospective cohort study

BackgroundWhole brain radiation therapy (WBRT) and stereotactic radiation therapy (SRT) are the two most common treatments for patients with intracranial metastatic disease (IMD). In Ontario, Canada, 4 of the 18 (22%) regional cancer centres (RCC) are fitted with dedicated cranial SRT program, which we refer to as SRT-dedicated program centres, while the remaining RCCs deliver SRT but lack a dedicated cranial SRT program. We hypothesized that SRT usage would be higher and patient outcomes better in RCCs with vs. those without an SRT-dedicated program. MethodsUsing administrative data housed at the Institute for Clinical Evaluative Sciences (IC/ES), we identified patients who had a primary cancer diagnosis and received cranial RT between April 1, 2010, and August 31, 2023. Treatment centres were grouped based on the presence or absence of an SRT-dedicated program. Within these groupings, hazard ratios (HR) for overall survival (OS) were compared. Additional comparisons based on the movement of patients across centres were performed. ResultsThe median OS of the cohort was 6.05 months. Significant differences in treatment and patient characteristics were observed according to RT modality used at RCCs with SRT-dedicated programs vs. those without, including the ratio of WBRT vs SRT (OR = 2.8, 95% CI 2.4-3.2, p < 0.0001), patient age (X2 = 38.2, df = 7, p < 0.0001), stage at diagnosis (X2=50.1, df = 4, p < 0.0001), and number of brain metastases treated (OR = 29.9, 95% CI 14.5-76.9, p < 0.0001). The median OS for patients treated with intracranial RT (WBRT or SRT) at centres with vs. those without a dedicated SRT programs was 7.20 vs 5.03 months (HR = 0.81, p < 0.0001), respectively. OS for patients who were treated with SRT at centres with vs. without a dedicated SRT program was 10.15 vs 7.89 months (HR = 0.88, p = 0.0275), respectively. No significant difference in the median OS for patients treated with WBRT at centres with or without a dedicated SRT program was observed (2.96 vs 3.09 months, HR = 1.08, p = 1.0, respectively). Mean OS for patients who travelled to a centre with a dedicated SRT program for intracranial RT after initial systemic therapy at a non-SRT-dedicated centre was associated with an positive impact on OS, compared to OS for patients who received systemic therapy and RT at a non-SRT-dedicated centre (14.0 vs 7.3 months, t = -3.9, p < 0.001). ConclusionOur study found greater utilization of SRT and significantly longer OS for patients with IMD treated in Ontario RCCs with an SRT-dedicated program. OS was not negatively impacted for patients who travelled to a centre with a dedicated SRT program for radiation therapy.