NI-8 LATE-DELAYED MRI FINDINGS AFTER RADIOTHERAPY: DOT-LIKE ENHANCED LESION

INTRODUCTION: Late-delayed radiation reactions after radiotherapy include brain atrophy, leukoencephalopathy, radiation necrosis, and cerebrovascular disease. We will discuss the contrast-enhanced SPGR to detect dot-like enhanced lesions that are considered to be late late-delayed radiation reactions. MATERIAL AND METHODS: One hundred eleven patients (62 males and 49 females; median age at irradiation: 49 years) who had received radiotherapy since 1994 and were alive since 2010, had dot-like lesions by contrast-enhanced SPGR, and had a PFS OS of at least 24 months were included in the study. Of these, 64 had high-grade glioma, 4 had low-grade glioma, 15 had PCNSL, 7 had metastatic brain tumors, 9 had germ cell tumors, 5 had medulloblastoma, and 7 had other tumors, with a mean follow-up of 89. RESULTS: Contrast-enhanced SPGR showed dot-like or rod-like findings in 23/111 patients (20.7%). Contrast-enhanced FIESTA and Flair-Cube were also detectable in some cases. However, it was difficult to detect by contrast SE-T1WI, SE-T2WI, or contrast SE-Flair. The lesions appeared a median of 49 months after irradiation (IQR 34, 103. Range 25-298). There were no lesions that increased in size, and multiple lesions appeared during the course of the study in 8/23 (34.8%) of the patients. All lesions occurred within the irradiated field and were seen in patients receiving a total dose of 50 Gy or more, but not in patients receiving whole-brain irradiation alone or whole-brain irradiation plus boost at 50 Gy or less. DISCUSSION AND CONCLUSION: It is difficult to elucidate the pathogenesis without pathological evidence, but it is one of the late-delayed radiation reactions that occur more than 2 years later, and it is presumed to be vasculopathy or granulation reaction in the Virchow-Robin space. It tends to increase over time and is not considered to be a condition that causes sudden clinical manifestations.