Brain FET PET tumor‐to‐white mater ratio to differentiate recurrence from post‐treatment changes in high‐grade gliomas
Ameya Puranik, Venkatesh Rangarajan, Indraja D. Dev, Yash Jain, Nilendu Purandare, Arpita Sahu, Amitkumar Choudhary, Tejpal Gupta, Abhishek Chatterjee, Aliasgar Moiyadi, Prakash Shetty, Sridhar Epari, Ayushi Sahay, Vijay Patil, Sneha Shah, Archi Agrawal
Abstract
BACKGROUND AND PURPOSE: Highergrade glial neoplasms undergo standard treatment with surgery, radiotherapy, and alkylating agents. There is often a clinical/neuroimaging dilemma in the post-treatment setting to differentiate disease recurrence from treatment-related changes. FET (fluoro-ethyl-tyrosine) PET has emerged as a molecular imaging modality for cases where MR imaging is inconclusive. This study aims to develop a cutoff on FET PET for differentiating true recurrence from post-treatment changes. METHODS: F-FET was injected and static imaging of the brain was performed at 20 min. A tumor-to-white matter (T/Wm) ratio was used as semiquantitative parameter. A T/Wm cutoff of 2.5 was used for image interpretation. Imaging findings were confirmed by either histopathologic diagnosis in a multidisciplinary joint clinic or based on follow-up of clinical and neuroimaging findings. RESULTS: Forty-one of 72 patients (57%) showed recurrent disease on FET PET. Thirty-five of them were confirmed to have tumor recurrence; six patients showed post-treatment changes. Thirty-one of 72 patients (43%) showed post-treatment changes on FET PET; 27 were confirmed as post-treatment change and four patients had tumor recurrence on subsequent MR imaging. An optimum T/Wm cutoff of 2.65 was derived based on receiver operating characteristic analysis with a sensitivity of 80% and specificity of 87.5%. CONCLUSION: Static FET PET can be used as problem-solving imaging modality with a T/Wm cutoff of 2.65 to differentiate late recurrence from post-treatment changes in grade 3 or 4 brain gliomas with equivocal MR features.