204 Chapter 8 Brain metastases (BMs) are a common occurrence in adult patients with cancer, affecting approximately 10-30% of patients.1–3 Advances in medical treatments and imaging techniques have led to earlier detection and improved survival rates for patients with BMs, making the population of affected patients only expected to increase in the coming years.4–6 The focus of patient-centered treatment has shifted towards balancing prolongation of life with quality of life (QoL). One of the cornerstones of medical treatment for BMs is radiotherapy. Despite efforts to minimize radiation dose to surrounding healthy tissue, the physical limitations of the radiotherapy technique and necessary safety margins make it impossible to avoid entirely. The dose in the surrounding healthy brain tissue can lead to radiation-induced brain injury and thereby cause cognitive decline, although the exact mechanisms remain unclear. PART I: NEUROCOGNITIVE FUNCTIONING IN PATIENTS WITH BRAIN METASTASES The two prominent strategies for radiotherapy in BMs are stereotactic radiosurgery (SRS) and whole-brain radiotherapy (WBRT). SRS employs high-precision localized irradiation to target BMs with minimal harm to surrounding, healthy brain tissue, while WBRT ensures coverage of all brain tissue and thereby sterilizes not-yet visible BMs. A significant disadvantage of WBRT is its potential to inflict radiationinduced tissue damage throughout the brain, which makes SRS preferred option in current clinical practice whenever possible.7–10 In Chapter 2 we compared previous literature on changes in cognitive functioning provoked by either WBRT or SRS in adult patients with non-resected BMs. Based on a systematic literature search and article screening process 20 articles reporting on 14 original datasets were analyzed. The majority of patients who underwent WBRT exhibited a consistent decline in cognitive performance from pre-radiotherapy to short-term follow-up (1-4 months), with a further decrease noted at mid-term follow-up (5-8 months). Only a subset of patients with better prognoses (e.g. those with lower pre-radiotherapy BMs volume and long-term survivors) exhibited stable or improved cognitive performance in the long-term (15 months). Conversely, approximately half of the studies revealed declined cognitive performance in patients during short-term follow-up after SRS. At both mid- and long-term follow-up studies consistently reported cognitive performance to be at pre-SRS levels. Thus, while cognitive-side effects of SRS appear to be transient, significant cognitive deterioration can occur in patients after WBRT. Thereby, the shift in treatment preference towards SRS is further substantiated by a lower risk of persistent cognitive side-effects with SRS.
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