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Local Control After Single-Isocenter Dynamic Conformal Arc SRS for Brain Metastases
Maciej Blok1,2, Izabela Zarebska1, Izabela Miechowicz3
1Franciszek Lukaszczyk Memorial Oncology Center, Department of Neurooncology and Radiosurgery, 85-796 Bydgoszcz, Poland.
Cancers
|November 27, 2025
Summary
Dynamic conformal arc single-isocenter, multi-target (DCA-SIMT) stereotactic radiosurgery provides excellent local control for multiple brain metastases. Key factors for success include conformity index and margin expansion, with systemic therapy enhancing outcomes.
Area of Science:
- Radiation Oncology
- Neurosurgery
- Medical Physics
Background:
- Brain metastases are a common complication of advanced cancer, posing significant treatment challenges.
- Whole-brain radiation therapy (WBRT) has limited efficacy and significant neurocognitive side effects.
- Stereotactic radiosurgery (SRS) has emerged as a preferred treatment, with advancements enabling efficient management of multiple lesions.
Purpose of the Study:
- To evaluate the local control rates of dynamic conformal arc single-isocenter, multi-target (DCA-SIMT) radiosurgery for multiple brain metastases.
- To identify factors influencing treatment outcomes in patients undergoing DCA-SIMT radiosurgery.
- To assess the role of geometric parameters and systemic therapies in local control.
Main Methods:
- Retrospective analysis of 195 brain metastases treated with DCA-SIMT SRS on a Varian TrueBeam LINAC.
- Treatment planning utilized Brainlab Elements MultiMets software with ExacTrac image guidance.
- Local control assessed via MRI (BM-RANO criteria); radiation-induced contrast enhancements (RICE) identified using multiparametric MRI.
Main Results:
- High local control at 6 months (93%) with 82% complete or partial response.
- Conformity index < 1.42 and margin expansion ≥ 0.5 mm were associated with improved local control.
- Systemic therapy (immunotherapy/targeted therapy) within 4 months post-SRS significantly increased radiographic response, especially in lung adenocarcinoma.
Conclusions:
- DCA-SIMT SRS is effective in achieving high local control for multiple brain metastases.
- Conformity index, margin expansion, and concurrent systemic therapy are crucial factors influencing outcomes.
- Further research is needed to optimize margins, particularly in scenarios with high distance-to-isocenter.
