Functional Magnetic Resonance Imaging-Guided Stereotactic Radiosurgery to Avoid Symptomatic Radionecrosis

Area of Science:

• Neurosurgery
• Radiology
• Neuro-oncology

Background:

• Functional magnetic resonance imaging (fMRI) offers superior localization of eloquent brain areas compared to structural imaging, aiding in neurosurgical planning.
• Despite its benefits, fMRI is underutilized in stereotactic radiosurgery (SRS) for brain metastases (BM).
• This study investigates the relationship between SRS dose to fMRI-identified eloquent areas and radionecrosis (RN) symptoms.

Purpose of the Study:

• To assess the neuroanatomic relationship between SRS for BM, nearby eloquent areas identified by fMRI, and symptoms of radionecrosis (RN).
• To evaluate the efficacy of a novel fMRI-guided SRS (fMRI-SRS) planning approach in minimizing dose to eloquent areas.

Main Methods:

• Patients with fMRI within three months of SRS for BM were included.
• The nearest eloquent area (NEA) was defined as the closest motor, language, or visual area on fMRI to the irradiated BM.
• Logistic regression analyzed the relationship between dose to the NEA and focal symptomatic RN (FSRN); cases were replanned using fMRI-SRS to maximize NEA avoidance.

Main Results:

• Among 93 patients, 12 developed FSRN. Higher V14Gy (single-fraction equivalent dose) to the NEA predicted increased FSRN risk (OR 6.8/mL, p=0.05) in patients receiving 5-fraction SRS.
• fMRI-SRS replanning reduced NEA V14Gy by a mean of 22.5% across all cases.
• The most common NEA was motor (76%), followed by language (19%).

Conclusions:

• Focal neurologic symptoms of RN are linked to SRS dose delivered to eloquent brain areas identified by fMRI.
• fMRI-SRS planning effectively minimizes radiation dose to critical eloquent areas.
• This approach holds potential for mitigating neurological toxicity in patients undergoing SRS for brain metastases.