Correlation of various quantitative parameters on FDG PET-CT in primary brain tumors with histopathological grades

Brain tumors are important cause of mortality and morbidity in children (30%) and young adults (20%). FDG PET detects metabolic activity of tumor, thereby aiding in complete tumor resection and also detection of tumor recurrence. FDG PET may have independent prognostic value in brain tumors. This study evaluated various quantitative parameters on FDG PET-CT and their association with postoperative histopathological grading in patients with brain tumors. Patients with clinically and/or radiologically suspected primary brain tumors were studied prospectively. Total 30 patients (23-males & 7-females) who underwent FDG PET-CT during February 2021- June 2022 and subsequent tumor excision were included. The mean age of patients included was 37.3 years (range 8-73 years). FDG PET-CT images were acquired post 45 minutes of intravenous 0.10-0.14mCi per kg of body weight of F18-FDG administration. Image analysis done by qualitative and quantitative methods. Various quantitative parameters in volume of interest (VOI) like SUVmax, mean & peak and relative parameters based on ratio of SUVs like tumor to white matter (T/W), tumor to grey matter (T/G), tumor to basal ganglia (T/B), tumor to cerebellum (T/C) and tumor to temporal lobe (T/T) were obtained and correlated with histological findings. Postoperative histopathological finding was taken as reference standard. Out of 30 patients who underwent surgery, 26 patients showed primary brain tumors in histopathology. 2 patients with benign lesions (epidermoid cysts), 1 patient with Ewing's sarcoma & another with lymphoma were excluded. All 26 patients showed abnormal FDG uptake in primary brain tumor region in the form of hypo, heterogeneous or hyper metabolism with corresponding CT abnormalities. Distribution of tumor histopathological grades and quantitative parameters were analyzed. The correlation coefficients were calculated using Pearson method. Several parameters SUVmax, SUVmean, SUVpeak and relative quantitative parameters based on SUV showed moderate correlation with WHO histopathological grades. Absolute parameter, SUVpeak and relative parameters, tumor to greymatter (T/G) & tumor to temporal lobe regions (T/T) ratios based on SUVpeak showed good correlation among the parameters. (author)