Abstract
Malignant central nervous system (CNS) tumors are often treated with radiation therapy, after which clinical and radiographic sequelae can lead to difficulties differentiating tumor recurrence from treatment effect. Magnetic resonance imaging (MRI) is often unable to distinguish between these two entities. The improved ability to delineate concerning foci could lead to earlier tumor detection with quicker access to new therapies and/or clinical trials; conversely, it could alleviate patient concerns in the case of radiation necrosis as the etiology. The utility of positron emission tomography with computed tomography (PET/CT) imaging with fluorodeoxyglucose (FDG) has been explored in CNS tumors in the past, as this imaging modality is widely used in oncologic practices. As there are concerns with false positive imaging in the case of cells with a high metabolic uptake due to causes other than malignancy (i.e. infection, inflammation), delayed FDG PET imaging has been proposed as a mechanism to reduce this confusion. Delayed FDG PET imaging has been explored in several adult and pediatric malignancies, including adult CNS tumors, though there are no current publications applying its use in pediatric CNS tumors. We present two cases of pediatric CNS tumors, where delayed FDG PET imaging helped in the early diagnosis of a recurrence through a distinguishing tumor from the treatment effect.
Highlights
Many central nervous system (CNS) tumors are treated with radiation therapy
The utility of positron emission tomography with computed tomography (PET/CT) imaging with fluorodeoxyglucose (FDG) has been explored in CNS tumors in the past, as this imaging modality is widely used in oncologic practices
We present two cases of pediatric CNS tumors, where delayed FDG Positron emission tomography (PET) imaging helped in the early diagnosis of a recurrence through a distinguishing tumor from the treatment effect
Summary
Many central nervous system (CNS) tumors are treated with radiation therapy. Treatmentinduced radiation necrosis can have clinical symptoms and radiographic findings very similar to brain tumor recurrence. They summarized prior reports, finding that FDG PET has been reported to be capable of distinguishing treatment necrosis from tumor recurrence with sensitivity and specificity in the ranges of 65%-81% and 40%-94%, respectively. She developed thrombotic microangiopathy as a complication following her second stem cell infusion, so she did not receive her third cycle of high-dose chemotherapy with stem cell rescue as originally planned, though she did require a stem cell boost for persistent reticulocytopenia and thrombocytopenia three months after her second Three months following her last round of chemotherapy, the patient underwent a disease evaluation with total spine and brain MRI, which revealed a new small enhancing lesion at C4-5 concerning for disease relapse versus radiation-induced change. FLAIR: fluid attenuated inversion recovery; FDG: fludeoxyglucose; PET: positron emission tomography
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