Novel radiotherapeutic strategies in the management of brain metastases: Challenging the dogma

Abstract

The role of radiation therapy in the management of brain metastasis is evolving. Advancements in machine learning techniques have improved our ability to both detect brain metastasis and our ability to contour substructures of the brain as critical organs at risk. Advanced imaging with PET tracers and magnetic resonance imaging-based artificial intelligence models can now predict tumor control and differentiate tumor progression from radiation necrosis. These advancements will help to optimize dose and fractionation for each patient's lesion based on tumor size, histology, systemic therapy, medical comorbidities/patient genetics, and tumor molecular features. This review will discuss the current state of brain directed radiation for brain metastasis. We will also discuss future directions to improve the precision of stereotactic radiosurgery and optimize whole brain radiation techniques to improve local tumor control and prevent cognitive decline without forming necrosis.

Keywords: artificial intelligence; brain metastases; cognitive preservation; stereotactic radiosurgery.

Figure 1.

Fifty-eight year old male patient with metastatic lung cancer with 28 brain lesions. Panel A and B are coronal and sagittal MRI post contrast volumetric sequences, respectively, with the radiation plan superimposed (yellow isodose line is 24 Gy, red isodose line is 12 Gy, blue isodose line is 8 Gy). Panel C is the dose volume histogram (green—Brain, GTV_total and PTV_total labeled in red).

Figure 2.

Panels A, B, and C are axial, coronal and sagittal MRI post contrast volumetric sequences, respectively. The orange contour is the memory avoidance structure (includes bilateral amygdala, bilateral hippocampi, fornix, corpus callosum, hypothalamus, pituitary). The dose color wash depicts a minimum dose of 3000 cGy, demonstrating excellent coverage of the brain while sparing the central memory structures.

Figure 3.

Sixty-three year old female patient with metastatic leiomyosarcoma status post prior fSRS to 9 brain lesions. Panel A demonstrates an F-18 fluciclivine PET revealing a right frontal mass with SUV_MAX of 2.7. Panel B depicts a heterogeneously enhancing mass with central necrosis in the frontal lobe. Panel C depicts a right frontal lesion with no elevated cerebral blood volume on T1 post-contrast imaging with dynamic contrast enhanced (DCE) perfusion imaging overlaid.