Changes in Brain Metastasis During Radiosurgical Planning.

Area of Science:

• Neuro-oncology
• Radiation Oncology
• Radiosurgery

Background:

• Brain metastases and tumor resection cavities can change in volume between initial imaging and treatment.
• Accurate targeting in radiosurgery (RS) is crucial for effective treatment and minimizing off-target effects.

Purpose of the Study:

• To assess volumetric changes in brain metastases and resection cavities between planning MRI and radiosurgery (RS).
• To determine if these changes necessitate alterations in management or the RS plan.

Main Methods:

• Patients undergoing RS for brain metastases or resection cavities had two MRIs: a planning MRI (MRI-1) and a verification MRI (MRI-2) 24 hours before RS.
• Changes in management or RS plan based on MRI-2 findings were recorded.

Main Results:

• 50% of patients (17/34) required a management change based on MRI-2.
• A delay of 8 days or more between scans increased the likelihood of management change to 78%, compared to 41% for delays of 7 days or less.
• 32 out of 59 lesions required replanning, most commonly due to increased tumor or cavity volume.

Conclusions:

• Brain metastases and resection cavities exhibit significant volumetric changes over short periods.
• Minimizing the interval between planning MRI and RS treatment is recommended to ensure treatment accuracy.