Differentiation of local tumor recurrence from radiation-induced changes after stereotactic radiosurgery for treatment of brain metastasis: case report and review of the literature

Abstract

BackgroundStructural follow-up magnetic resonance imaging (MRI) after stereotactic radiosurgery (SRS) for brain metastases frequently displays local changes in the area of applied irradiation, which are often difficult to interpret (e.g., local tumor recurrence, radiation-induced changes). The use of stereotactic biopsy for histological assessment of these changes has a high diagnostic accuracy and can be considered as method of choice. In order to solve this relevant clinical problem non-invasively, advanced MRI techniques and amino acid positron-emission-tomography (PET) are increasingly used.Case presentationWe report the long-term follow-up of a patient who had been treated with linear accelerator based SRS for cerebral metastases of a lung cancer. Fifty-eight months after SRS, the differentiation of local recurrent brain metastasis from radiation-induced changes using structural MRI was difficult. For further differentiation, perfusion-weighted MRI (PWI), proton magnetic resonance spectroscopy (MRS), and 11C-methyl-L-methionine (MET) PET was performed. Due to artifacts and technical limitations, PWI MRI and MRS findings were not conclusive. In contrast, MET PET findings were suggestive for radiation-induced changes. Finally, a stereotactic biopsy for histological assessment of these changes demonstrated clearly a radiation-induced necrosis and the absence of vital tumor.ConclusionThe use of stereotactic biopsy for histological assessment of indistinguishable lesions on structural MRI after SRS for treatment of brain metastasis represents a highly reliable method to differentiate local tumor recurrence from radiation-induced changes. In this field, results of studies with both advanced MRI techniques and amino acid PET suggest encouraging results. However, artifacts and technical limitations (e.g., lesion size) are still a problem and comparative studies are needed to investigate the relationship, diagnostic performance, and complementary character of advanced MRI techniques and amino acid PET.

DynamicO-(2-18F-fluoroethyl)-L-tyrosine positron emission tomography differentiates brain metastasis recurrence from radiation injury after radiotherapy

“…[10][11][12][13][14][15] In these studies, data evaluation was based predominantly on static PET parameters (eg, tumor-to-brain ratios).…”

Brain: Radiotherapy

“…As these are similar findings in tumor recurrence and progression, the differentiation between tumor-related and treatment-related effects is a challenge for conventional imaging including CT and MRI (Fig. 3) (Reddy et al 2013;Patel et al 2011;Essig et al 2011;Kickingereder et al 2013). The timing for treatment-induced changes varies significantly in this respect, and even relative lateoccurring changes can resolve completely.…”

Diagnostic imaging of intracranial metastasis

“…In contrast, high grade glioma capillaries have a varied morphology which tend to simulate normal brain vessels with a blood-brain barrier but with variable permeability [52,51]. However, primary CNS lymphoma demonstrates the greatest vascular permeability compared to high grade glioma and metastatic disease, likely due to the characteristic perivascular concentration of lymphoma cells and the propensity for the malignancy to invade and disrupt the vessel basement membrane [53,54]. MR spectroscopy has shown differences in metabolites within high grade gliomas, lymphomas, and metastases with variable ability to differentiate these tumors, but with notable differences including the frequent absence of creatinine in metastases compared to high grade glioma, and differences in lipid and macromolecules in high grade gliomas compared to metastases [47,[55][56][57][58][59][60][61]30].…”