Abstract
BACKGROUND
It is challenging to discriminate radiation necrosis from tumor progression, especially in malignant glioma. Therefore many radiological imaging studies have been reported. In this study, we performed a systematic review of radiological diagnosis for radiation necrosis and analyzed the best radiological imaging for malignant glioma.
METHODS
We divided diagnostic approaches into two categories as follows-CT and MRI (conventional radiological imaging studies), and SPECT and PET (nuclear medicine studies). Our librarians conducted a comprehensive systematic search on Pub Med, Cochrane Library, and the Japan Medical Abstract Society up to March 2015. The searching keywords included radiation necrosis, recurrence, imaging modalities such as MRI, diagnosis, and differential. In a meta-analysis, diagnostic odds ratio (DOR) was calculated. A subanalysis was performed, dividing into tumor types, gliomas and metastatic brain tumors.
RESULTS
Of 188 and 239 records extracted from the database, 20 and 26 studies were included in the meta-analysis after exclusion of case reports and studies with incompatible content and insufficient information. Gd-enhanced MRI exhibited the lowest sensitivity (63%) and DOR (2.2). On the other hand, combined multiple imaging studies including MRS and perfusion image displayed the highest sensitivity (96%) and DOR (5.9). In the subanalysis for glioma, Gd-enhanced MRI and 18F-FDG-PET revealed low DORs (1.7 and 2.3). Conversely, 18F-FET-PET and combined multiple imaging studies showed high DORs (6.8 and 5.9).
CONCLUSIONS
Gd-enhanced MRI had low diagnostic ability for differentiation of radiation necrosis. In glioma patients, 18F-FDG-PET was not useful to discriminate radiation necrosis from tumor progression. Combined multiparametric imaging including lesional metabolism and blood flow could enhance diagnostic accuracy and be useful to differentiate radiation necrosis from tumor progression even in glioma patients.
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