RT-7 DIFFERENTIATION AND TREATMENT OF RECURRENCE AND RADIATION NECROSIS IN THE TREATMENT OF MALIGNANT GLIOMAS

In the course of treatment of malignant gliomas, the appearance of contrast-enhanced lesions and surrounding T2/FLAIR high-signal after treatment is often experienced. There is no modality that can reliably diagnose whether the lesion is a recurrence or a response to treatment, including radiation necrosis. Furthermore, the choice of treatment modality is often difficult, such as reexcision, stereotactic irradiation, Avastin. Very few reports have examined the relationship between the irradiation field and histology.

Thirty-seven lesions in 30 patients who underwent repeat resection of malignant gliomas at our institution from October 2019 to December 2021 were analyzed retrospectively. Based on postoperative pathology, the patients were classified into two groups: recurrence group and radiation necrosis group.In each group, age, gender, histology at initial surgery, IDH status, radiation and chemotherapy, TNR of Methionine-PET, and the number of days after the end of treatment until the appearance of contrast lesions were considered.

The recurrence group consisted of 20 patients with 26 lesions, mean age 48 years, male/female = 13/7, pathology was GBM 13, DA 1, AA 3, AO 2, AE 1, TNR 3.33 (1.41-6.32), and time to contrast appearance 547 (14-2427) days. PDT in combination with initial surgery was seen in 9 patients.The necrosis group consisted of 10 patients with 11 lesions, mean age 47 years, male/female = 4/6, pathology GBM 5, AA 2, AO 1, PXA 2. TNR 2.51 (1.20-3.75), 318 (24-678) days to contrast appearance, 2 patients had PDT.

Radiation necrosis tended to have lower TNR and shorter time to lesion appearance than recurrence, but no significant difference was observed. Improvement of diagnostic accuracy with modalities is desirable, and unnecessary irradiation is highly likely to contribute to ADL deterioration such as leukoencephalopathy and higher functional impairment.