Responses in the diffusivity and vascular function of the irradiated normal brain are seen up-until 18 months following SRS of brain metastases. Issue 2 (28th February 2020)

• Record Type: Journal Article
• Authors: Nilsen, Line Brennhaug; Digernes, Ingrid; Grøvik, Endre; Saxhaug, Cathrine; Latysheva, Anna; Geier, Oliver; Breivik, Birger; Sætre, Dag Ottar; Jacobsen, Kari Dolven; Helland, Åslaug; Emblem, Kyrre Eeg
• Is Part Of: Neuro-oncology advances. Volume 2:Issue 2(2020)
• Publication Date: 2020-02-28
• Subjects: stereotactic radiosurgery -- normal-appearing brain tissue response -- brain metastases -- diffusion-weighted MRI -- perfusion MRI; 616.99481
• DOI: 10.1093/noajnl/vdaa028
• Languages: English
• ISSNs: 2632-2498

Abstract

Abstract: Background: MRI may provide insights into longitudinal responses in the diffusivity and vascular function of the irradiated normal-appearing brain following stereotactic radiosurgery (SRS) of brain metastases. Methods: Forty patients with brain metastases from non-small cell lung cancer (N=26) and malignant melanoma (N=14) received SRS (15-25Gy). Longitudinal MRI was performed pre-SRS and at 3, 6, 9, 12, and 18 months post-SRS. Measures of tissue diffusivity and vascularity were assessed by diffusion-weighted and perfusion MRI, respectively. All maps were normalized to white matter receiving<1Gy. Longitudinal responses were assessed in normal-appearing brain, excluding tumor and edema, in the LowDose (1-10Gy) and HighDose (>10Gy) regions. The ECOG (Eastern Cooperative Oncology Group) performance status was recorded pre-SRS. Results: Following SRS, the diffusivity in the LowDose region increased continuously for one year (105.1%±6.2%; P<0.001), before reversing towards pre-SRS levels at 18 months. Transient reductions in micro-vascular cerebral blood volume (P<0.05), blood flow (P<0.05) and vessel densities (P<0.05) were observed in LowDose at 6-9 months post-SRS. Correspondingly, vessel calibers in LowDose transiently increased at 3-9 months (P<0.01). The responses in HighDose displayed similar trends as in LowDose, but with larger inter-patient variations. Vascular responses followed pre-SRS ECOG status. Conclusions: Our results imply that even low doses of radiation to normal-appearing brain following cerebral SRS induce increased diffusivity and reduced vascular function for up-until 18 months. In particular, the vascular responses indicate reduced ability of the normal-appearing brain tissue to form new capillaries. Assessing the potential long-term neurologic effects of SRS on the normal-appearing brain is warranted.