Introduction The event-free survival in pediatric anaplastic large cell lymphoma (ALCL) remains at 70% irrespective of the diverse chemotherapy regimens used. There is lack of valid prognostic factors identifying high-risk patients. We investigated the prognostic value of baseline metabolic parameters and interim response on 18F-FDG PET/CT in pediatric ALCL patients. Methods We retrospectively reviewed 40 pediatric ALCL patients with paired 18F-FDG PET/CT and treated uniformly on vinblastine-based institution protocol. The SUVmax, SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis of the lymphomatous lesion were measured. Continuous PET parameters were stratified by their median values. Deauville scoring system was used to assess response to chemotherapy in the interim scan. Prognostic factors for overall survival (OS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method, log-rank test, and Cox proportional hazards model. Results At median follow-up of 52 months, 13 patients died and 13 had recurrence. On univariate analysis, higher whole-body MTV (WBMTV) and partial response on interim scan were statistically associated with OS. High-risk features, WBMTV, and partial response were statistically associated with DFS. On multivariate analysis combining baseline characteristics and interim response, interim response (hazard ratio, 3.56; P = 0.034) was statistically significant for OS. Multivariate analysis for DFS using only baseline characteristics revealed WBMTV as statistically significant (hazard ratio, 4.08; P = 0.035), but none of the parameters was statistically significant when baseline characteristics and interim response were evaluated together. Conclusions Whole-body tumor burden assessment with MTV and interim response may help to identify high-risk patients who might get benefitted from intensive therapy.
Purpose To determine predictive models (PM) that could improve the accuracy for identifying metastatic regional nodes in non-small cell lung cancer based on both PET and CT findings seen on 18F-FDG PET CT. Methods Three hundred thirty-nine biopsy-proven NSCLC patients who underwent surgical resection and had a staging 18F-FDG PET CT were enrolled. PET parameters obtained were (1) presence of visual PET positive nodes, (2) SUVmax of nodes (NSUV), (3) ratio of node to aorta SUVmax (N/A ratio) and (4) ratio of node to primary tumour SUVmax (N/T ratio). CT parameters obtained were (1) short-axis diameter and (2) Hounsfield units (HU) of PET-positive nodes. PET and CT parameters were correlated with nodal histopathology to find out the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy. Different PM combining these parameters were devised and the incremental improvement in accuracy was determined. Results Visual PET positivity showed sensitivity, specificity, PPV, NPV and accuracy of 72.4, 76.1, 30.1, 95.1 and 75.6, respectively. PM2 which combined visual PET positivity, NSUV and HU appears more clinically relevant and showed sensitivity, specificity, PPV, NPV and accuracy of 53.5, 96.5, 68.9, 93.6 and 91.2, respectively. PM6 which combined visual PET positivity, NSUV, N/A ratio and HU showed the maximum PPV (80.0%), specificity (98.3%) and accuracy of (91.9%). Conclusion PM combining parameters like nodal SUVmax, N/A ratio, N/T ratio and HU values have shown to improve the PPV, specificity and overall accuracy of 18FDG PET CT in the preoperative diagnosis of nodal metastases.
High-grade gliomas, metastases, and primary central nervous system lymphoma (PCNSL) are common high-grade brain lesions, which may have overlapping features on magnetic resonance (MR) imaging. Our objective was to assess the utility of 18-fluoride-fluoro-ethyl-tyrosine positron emission tomography (FET-PET) in reliably differentiating between these lesions, by studying their metabolic characteristics. Patients with high-grade brain lesions suspicious for glioma, with overlapping features for metastases and PCNSL were referred for FET-PET by Neuroradiologists from Multidisciplinary Neuro-Oncology Joint Clinic. Tumor-to-contralateral white mater ratio (T/Wm) at 5 and 20 min was derived and compared to histopathology. Receiver operating characteristic curve analysis was used to find the optimal T/Wm cutoff to differentiate between the tumor types. T/Wm was higher for glial tumors compared to nonglial tumors (metastases, PCNSL, tuberculoma, and anaplastic meningioma). A cutoff of 1.9 was derived to reliably diagnose a tumor of glial origin with a sensitivity and specificity of 93.8% and 91%, respectively. FET-PET can be used to diagnose glial tumors presenting as high-grade brain lesions when MR findings show overlapping features for other common high-grade lesions.
18F flurodeoxyglucose positron emission tomography-computed tomography (18F FDG PET-CT) is widely used in the evaluation of patients with lung mass suspicious for malignancy. In addition to malignancy, a variety of benign neoplasms and inflammatory lesions can arise in the lungs, many of which show increased FDG concentration, thereby mimicking malignancy. Awareness of the common mimics of lung cancer and a thorough understanding of their key imaging characteristics on CT as well as FDG PET is helpful in narrowing the differential diagnosis, eventually leading to appropriate therapy. In this article, we enlist these mimics and discuss their metabolic and morphologic characteristics and provide a pathophysiological basis for their FDG uptake.
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