title: Dual time point fluorodeoxyglucose positron emission tomography/computed tomography in differentiation between malignant and benign lesions in cancer patients. Does it always work?
abstract: OBJECTIVE
  Assess the added value of dual time point F-18-fluorodeoxyglucose positron emission tomography/computed tomography (DTP F-18-FDG-PET/CT) in the differentiation of malignant from a benign lesion in cancer patients.
  
  
  METHODS
  Totally, 140 F-18-FDG PET/CT scans of 60 cancer patients who underwent DTP protocol (early whole body PET/CT [E] at 60 min [range, 45-76 min] and delayed limited PET/CT [D] on areas of interest at 120 min [range, 108-153 min] after the tracer injection) were retrospectively reviewed. Visual and semi-quantitative analysis was performed on both early and delayed images. All findings were confirmed by histopathology and/or at least 3 months follow-up (F-18-FDG PET/CT, CT, or magnetic resonance imaging). The result was considered true positive (TP) if delayed standardized uptake value (SUV) of suspicious lesions increased and confirmed to be malignant, false positive (FP) if delayed SUV increased and confirmed to be benign, true negative (TN) if delayed SUV unchanged or decreased and confirmed to be benign, and false negative (FN) if delayed SUV unchanged or decreased and confirmed to be malignant.
  
  
  RESULTS
  A total of 164 suspicious lesions were detected (20 presacral lesions, 18 lung nodules, 18 Hodgkin's disease (HD) lesions, 16 rectal lesions, 16 head and neck (H and N) lesions, 14 hepatic lesions, 14 non-Hodgkin's lymphoma (NHL) lesions, 12 mediastinal lymph nodes (LNs), 10 focal gastric uptake, 10 soft tissue lesions, 8 breast lesions, 4 peritoneal nodule, and 4 others). Sixty-four lesions were pathologically confirmed, and 100 lesions were confirmed based on 3-6 months follow-up. There were 62 TP lesions, 44 FP, 58 TN and no FN results. The overall sensitivity was 100% of DTP F-18-FDG PET/CT in detecting suspicious lesions. The specificity was 57% in differentiating malignant from benign lesions, and the accuracy was 73%. Positive predictive value was 59%, negative predictive value (NPV) 100%. All hepatic lesions were TP. Accuracy in metastatic hepatic lesions HD, presacral soft tissue, lung nodules, H, and N cancer, breast cancer, NHL and mediastinal LN was100%, 88.8%, 80%, 78%, 75%, 75%, 71%, and 33.3%, respectively.
  
  
  CONCLUSIONS
  DTP F-18-FDG-PET/CT protocol does not always work in differentiation between benign and malignant lesions. However; it has high NPV, and promising results was noted in hepatic lesions, lymphoma, and recurrent rectal cancer.
authors.affiliation: Department of Clinical Oncology and Nuclear Medicine, Faculty of Medicine, Assiut University, Assiut, Egypt, Saudi Arabia ; Department of Radiology, Division of Nuclear Medicine, Prince Sultan Military Medical City, Riyadh, Saudi Arabia.
authors.forename: Hussein Rabie
authors.initials: HR
authors.lastname: Saleh Farghaly
authors.affiliation: Department of Clinical Oncology and Nuclear Medicine, Faculty of Medicine, Assiut University, Assiut, Egypt, Saudi Arabia.
authors.forename: Mohamed Hosny
authors.initials: MH
authors.lastname: Mohamed Sayed
authors.affiliation: Department of Oncology and Nuclear Medicine, Nuclear Medicine Unit, Kasr Al-Aini - Cairo University Hospital, Cairo, Egypt.
authors.forename: Hatem Ahmed
authors.initials: HA
authors.lastname: Nasr
authors.affiliation: Department of Clinical Oncology, Faculty of Medicine, Sohag University, Sohag, Egypt.
authors.forename: Ahmed Marzok
authors.initials: AM
authors.lastname: Abdelaziz Maklad
keywords: Delayed limited positron emission tomography/computed tomography; F-18-fluorodeoxyglucose positron emission tomography/computed tomography; dual time point