Brain MR findings in patients treated with particle therapy for skull base tumors

Abstract

Nowadays, hadrontherapy is increasingly used for the treatment of various tumors, in particular of those resistant to conventional radiotherapy. Proton and carbon ions are characterized by physical and biological features that allow a high radiation dose to tumors, minimizing irradiation to adjacent normal tissues. For this reason, radioresistant tumors and tumors located near highly radiosensitive critical organs, such as skull base tumors, represent the best target for this kind of therapy. However, also hadrontherapy can be associated with radiation adverse effects, generally referred as acute, early-delayed and late-delayed. Among late-delayed effects, the most severe form of injury is radiation necrosis. There are various underlying mechanisms involved in the development of radiation necrosis, as well as different clinical presentations requiring specific treatments. In most cases, radiation necrosis presents as a single focal lesion, but it can be multifocal and involve a single or multiple lobes simulating brain metastasis, or it can also involve both cerebral hemispheres. In every case, radiation necrosis results always related to the extension of radiation delivery field. Multiple MRI techniques, including diffusion, perfusion imaging, and spectroscopy, are important tools for the radiologist to formulate the correct diagnosis. The aim of this paper is to illustrate the possible different radiologic patterns of radiation necrosis that can be observed in different MRI techniques in patients treated with hadrontherapy for tumors involving the skull base. The images of exemplary cases of radiation necrosis are also presented.

Particle Radiotherapy for Skull Base Chondrosarcoma: A Clinical Series from Italian National Center for Oncological Hadrontherapy

“…This should be taken into consideration, especially when compared with older studies, when MRI was not always a routine exam in follow-up and when not all recent and advanced techniques, including diffusion, perfusion imaging, and spectroscopy, were performed. Moreover, in our series, we reported every radiological change in white matter, whether they manifested with edema, with contrast enhancement or with areas of necrosis [37], regardless of the clinical symptoms. In the comparison of the radio-induced brain changes' rates among different series, the criteria adopted to estimate, to rate and to term this outcome can be rather heterogeneous.…”

Study of relationship between dose, LET and the risk of brain necrosis after proton therapy for skull base tumors

“…Brain radiographic changes were defined as contrast-enhancing brain lesions (CEBL), which were delineated by a medical doctor using the first MRI images where changes have been detected. Based on MRI, such patients were then diagnosed with symptomatic or non-symptomatic brain changes, which according to Late Effects Normal Tissue Task Force subjective, objective, management and analytic (LENT-SOMA) were divided into edema (necrosis grade 1, mostly visible on T2/FLAIR acquisitions [22], [23]) or/and necrosis grade from 2 to 3 structure (identified on T1 acquisitions with contrast). Table 1 summarizes the characteristics of patients showing CEBL.…”

Atlas construction and spatial normalisation to facilitate radiation-induced late effects research in childhood cancer

“…For example, this could be done by evaluating the accuracy of mapping anatomical landmarks, or by dividing organs into well-defined sub-structures that can be analysed separately. Improving localised mapping is increasingly relevant for clinical endpoints such as brain injury (Gunther et al 2015 , Viselner et al 2019 ), lung fibrosis (Veiga et al 2018 ) and heart failure (McWilliam et al 2017 ). We recommend that in clinical studies investigating organ-specific end-points additional validation is performed accordingly.…”