Introduction: Although widely employed, gadolinium enhanced MR imaging using the Macdonald criteria has previously been shown to be of limited value in differentiating brain tumor recurrence from pseudoprogression due to therapeutic effects of irradiation and chemotherapy. Metabolic imaging (FET-PET) or computed tomography (CT) perfusion studies could help differentiate pseudoprogression from tumor recurrence
Methods: At the time of abstract submission, 11 patients (7 male, 4 female) presenting with new or increased contrast enhancement on follow-up MR imaging after surgical resection and adjuvant chemo- and/or radiotherapy were enrolled in this ongoing non-randomized prospective case study. All subjects underwent CT perfusion and FET-PET imaging. Results were evaluated independently by two investigators. Predictive values of either modality were established using histopathology results in patients undergoing subsequent surgery or by employing RANO criteria in those continuing follow-up.
Results: On CT perfusion imaging, 21 patients were diagnosed with tumor recurrence and 3 patients were found to show pseudoprogression. FET-PET demonstrated tumor recurrence in 22 patients, with therapy induced changes occurring in 2 patients. CT perfusion and FET-PET diagnoses differed in 3 out of 24 patients (12.5%). Histopathology results are currently available for 7 patients, all demonstrating anaplastic astrocytoma recurrences – this was correctly predicted by FET-PET imaging for all patients, while CT perfusion predicted pseudoprogression in one case and tumor recurrence in all other cases. As this is an ongoing study, further results from histopathology and RANO criteria are still pending.
Conclusions: This study evaluates the clinical usefulness and potential superiority of either CT perfusion or FET-PET imaging as a predictive tool in differentiating pseudoprogression from tumor recurrence in malignant gliomas. Detailed results for 24 patients will be submitted by May 2011.
Patient Care: Depending on the outcome we would be able to better distinguish pseudoprogression from tumor recurrence and thereby aid in the decision making process surgeons face when evaluating non-conclusive MR imaging results. This will possibly improve outcomes and reduce morbidities from unwarranted surgical explorations or prolonged watch-and-wait
Learning Objectives: - technically differentiate CT perfusion and FET-PET
- understand the usefulness of either modality in predicting tumor recurrence
- evaluate clinical usefulness as a tool to help surgeons making treatment decisions in the management of glioma patients