Abstract
Radionecrosis (RN) is the most important side effect after stereotactic radiotherapy (SRT) for brain metastases, with a reported incidence ranging from 3% to 24%. To date, there are no unanimously accepted criteria for iconographic diagnosis of RN, as well as no definitive dose-constraints correlated with the onset of this late effect. We reviewed the current literature and gave an overview report on imaging options for the diagnosis of RN and on dosimetric parameters correlated with the onset of RN. We performed a PubMed literature search according to the preferred reporting items and meta-analysis (PRISMA) guidelines, and identified articles published within the last ten years, up to 31 December 2019. When analyzing data on diagnostic tools, perfusion magnetic resonance imaging (MRI) seems to be very useful allowing evaluation of the blood flow in the lesion using the relative cerebral blood volume (rCBV) and blood vessel integrity using relative peak weight (rPH). It is necessary to combine morphological with functional imaging in order to match information about lesion morphology, metabolism and blood-flow. Eventually, serial imaging follow-up is needed. Regarding dosimetric parameters, in radiosurgery (SRS) V12 < 8 cm3 and V10 < 10.5 cm3 of normal brain are the most reliable prognostic factors, whereas in hypo-fractionated stereotactic radiotherapy (HSRT) V18 and V21 are considered the main predictive independent risk factors of RN.
Highlights
Brain metastases represent the most frequent intracranial tumor with an incidence of up to 35%
Stereotactic radiotherapy (SRT) is an ablative treatment based on the delivery of high doses per fraction to the target, and one of the most important and serious side effects in the brain is represented by radionecrosis (RN), with a reported incidence in the literature ranging from 3% to 24% [3,4,5,6]
Many studies have focused on RN after stereotactic radiotherapy for brain metastases, trying to identify reliable diagnostic tools and specific predictive dosimetric factors
Summary
Brain metastases represent the most frequent intracranial tumor with an incidence of up to 35%. They considerably affect quality of life in cancer patients because of the onset of several symptoms, such as seizures, focal neurological deficits or signs of intracranial hypertension, based on location and size [1]. Radiotherapy has an important role in the management of brain metastases. An important issue related to RN is the differential diagnosis with tumor progression, which is a key challenge for the management of patients who have undergone SRT for brain metastases. Anticoagulants, hyperbaric oxygen therapy, and bevacizumab can be considered, but the role of these therapies has yet to be defined
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