Utility of Magnetic Resonance Perfusion Imaging in Quantifying Active Tumor Fraction and Radiation Necrosis in Recurrent Intracranial Tumors

Background Ancillary criteria to identify tumor recurrence such as the McDonald criteria or Response Assessment in Neuro-Oncology criteria can provide false diagnoses. Magnetic resonance perfusion (MRP) imaging has been proposed to differentiate post-treatment changes from recurrence. We investigated the utility of MRP to quantify the histological fraction of active tumor (AT), treatment-related changes, and radiation necrosis in recurrent post-treatment intracranial tumors. Methods We conducted an exploratory single-blind study of patients with intracranial glioblastoma or metastases with previous radiation therapy and MRP before surgery. Biopsy specimens (n = 19) were analyzed for the percentage of AT, radiation necrosis, and treatment effect. Nonparametric Spearman's rho analysis and multivariable analysis of covariance were performed to assess the correlation between quantitative MRP and AT histological fraction. Results The mean patient age was 58 ± 11.5 years. The mean relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) were 1.33 ± 0.71 and 1.34 ± 0.73, respectively. On analysis of covariance, significant associations were identified between increased rCBF (P = 0.0004) and increased rCBV (P = 0.007) and percentage of AT. A significant interaction was identified between rCBF and rCBV and tumor histological features (glioblastoma vs. metastases; P = 0.003 and P = 0.03, respectively). An rCBF >1 predicted a mean AT fraction of ≥53% for all intracranial tumors and 74% for glioblastoma. Conclusion MRP can help quantitatively predict tumor recurrence and/or progression for glioblastomas. The AT histological fraction correlated with quantitative radiologic measurements, including rCBV and rCBF. For metastases, MRP might not be as useful in predicting the AT fraction. Clinicians must be judicious with their use of MRP in predicting tumor recurrence and radiation necrosis.