Early Postoperative Expansion of Parenchymal High-intensity Areas on T(2)-weighted Imaging Predicts Delayed Cerebral Edema Caused by Carmustine Wafer Implantation in Patients with High-grade Glioma

BACKGROUND: Carmustine (BCNU) wafer (Gliadel(®) Wafer) implantation after tumor resection is an approved treatment for high-grade glioma (HGG). These wafers change various characteristics on early postoperative magnetic resonance imaging (ep-MRI) including slight expansion of high-intensity areas on T(2)-weighted imaging (ep-T(2)-HIAs) into adjacent parenchyma without restricted diffusivity. We assessed the frequency of the ep-T(2)-HIAs after BCNU wafer implantation in HGG patients. Moreover, we focused on ep-T(2)-HIA expansion and its relation to delayed cerebral edema. METHODS: Twenty-five consecutive HGG patients who underwent BCNU wafer implantation were assessed. First, patients were divided into ep-T(2)-HIA and non-ep-T(2)-HIA groups, and the incidence of delayed adverse effects was compared between the two groups. Subsequently, the patients were divided into delayed edema and non-delayed edema groups, and pre-, intra-, and postoperative data were compared between the two groups. RESULTS: The ep-T(2)-HIA expansion and the delayed edema were evident in 9 cases (36%) and 12 cases (48%), respectively. In comparison of the ep-T(2)-HIA and non-ep-T(2)-HIA groups, delayed edema was the only delayed adverse effect associated with ep-T(2)-HIA expansion (P = 0.004). Univariate analysis showed a significantly higher ratio of delayed edema in the subgroups with maximal diameter of removed cavity ≤40 mm (P = 0.047) and the ep-T(2)-HIA expansion in comparison of the delayed edema and non-delayed edema groups. Multivariate analysis showed that the ep-T(2)-HIA expansion was the only independent factor associated with delayed edema (P = 0.021). CONCLUSION: In BCNU wafer implantation cases, ep-T(2)-HIA expansion was a predictive factor for delayed cerebral edema.