NIMG-42. RECURRENT TUMOR AND TREATMENT-INDUCED EFFECTS HAVE DIFFERENT MR SIGNATURES IN CONTRAST ENHANCING AND NON-ENHANCING LESIONS OF HIGH-GRADE GLIOMAS

BACKGROUND: Differentiating treatment-induced injury from recurrent high-grade glioma is an ongoing challenge in neuro-oncology in part due to lesion heterogeneity. This study aimed to determine whether different MR features were relevant for distinguishing recurrent tumor from the effects of treatment in contrast-enhancing (CEL) and non-enhancing lesions (NEL). METHODS: This prospective study analyzed 291 tissue samples (222 recurrent tumor; 69 treatment-effect) with known coordinates on imaging from 139 patients that underwent preoperative 3T MRI and surgery for a suspected recurrence. 8 MR parameter values from perfusion-weighted, diffusion-weighted, and MR spectroscopic imaging at each tissue sample location were tested for association with histopathological outcome using generalized estimating equation models for CEL and NEL tissue samples. Individual cutoff values were evaluated using ROC-Curve analysis with 5-fold cross-validation. RESULTS: In tissue samples obtained from the CEL, elevated relative cerebral blood volume (rCBV) was associated with the presence of recurrent tumor pathology (p<0.03), while increases in normalized choline (nCho) and choline-to-NAA index (CNI) were associated with the presence of recurrent tumor pathology in NEL tissue samples (p<0.008). A mean CNI cutoff value of 2.7 had the highest performance, resulting in mean sensitivity and specificity of 0.61 and 0.81 for distinguishing treatment-effect from recurrent tumor within the NEL. CONCLUSION: Although our results support prior work that underscores the utility of rCBV in distinguishing the effects of treatment from recurrent tumor within the contrast enhancing lesion, we found that metabolic parameters may be better at differentiating recurrent tumor from treatment-related changes in the NEL of high-grade gliomas.