Intraoperative Radiotherapy in Patients With Brain Metastases

1. INTRODUCTION

Brain metastases occur in roughly 30% of all cancer patients during their course of disease. Their incidence is believed to rise due to the aging population that develops more cancer per se, an increase in overall survival due to more effective extracranial therapies but with only few (novel) substances crossing the blood-brain barrier and more broadly available and more advanced imaging techniques.

Neurosurgical treatment remains a cornerstone in the management of brain metastasis, especially for lesions causing mass effects or neurological deficits or in case tissue is necessary to establish a diagnosis. As local recurrence rates are as high as 50-60% after surgical resection alone, adjuvant therapies to prevent such are necessary.

Whole brain radiotherapy (WBRT) does not influence survival but rather impairs neurocognitive functions and, as histologic in-depth exams of cavity borders showed that most brain metastases infiltrate only 0.3-1.2 mm into the surrounding healthy brain tissue, therefore treatment is to date usually confined to the cavity margin. Thus, the currently recommended standard of care is post-operative stereotactic radiosurgery (SRS) to the resection cavity. One of the drawbacks of this modality is the incidence of radionecrosis, especially in large tumor volumes. As an alternative to radiosurgery, hypofractionated local radiotherapy is also used, reducing the risk of radionecrosis in large volumes. There are no prospective randomized studies comparing both techniques.

The need to find a modality of radiotherapy that achieves al least the efficacy of radiosurgery or hypofractionated local radiotherapy, without the disadvantages thereof, makes IORT as a possible treatment alternative.