Detection of incidental colorectal tumours with 18F‐labelled 2‐fluoro‐2‐deoxyglucose positron emission tomography/computed tomography scans: results of a prospective study

Aim This study assessed the clinical significance of incidental colorectal 2‐fluoro‐2‐deoxyglucose (FDG) uptake using ¹⁸F‐FDG positron emission tomography/computed tomography (PET/CT) scans and evaluated the importance of colonoscopy when incidental colorectal FDG uptake was observed. Method A prospective study was designed and conducted at a single institution over a 2‐year period. In patients undergoing PET/CT scans, all with FDG uptake in the colorectum were assigned to have colonoscopy and biopsy. The value of PET/CT scanning was studied by comparison with the colonoscopy and biopsy results. Results Among 10 978 PET/CT scans, one or more focal uptakes of FDG in the colorectum were observed in 148 (1.35%) patients. In 136 valid patients, malignant colorectal tumours and polyps were found in 23.5% and 20.5%, respectively,, while the colon in the other 56% was normal. A higher false‐positive rate was found in the right colon compared with the distal colorectum (66.2%vs 36.7%, P = 0.004). A significant increase of the maximum standardized uptake (SUVmax) value was found among normal, polyps and cancer groups. Multivariate analysis revealed that SUVmax was the risk factor for predicting colorectal cancer or polyps and FDG uptake in the right colon was a negative predictive factor for finding cancers or polyps. Conclusions Our study proves the necessity of colonoscopy when incidental FDG uptake is found on PET/CT imaging. The false‐positive FDG uptake is more commonly observed in the right colon. Although the SUVmax value is higher in cancer patients, a high SUVmax value does not necessarily result in malignancies.     

Clinical value of whole body fluorine‐18 fluorodeoxyglucose positron emission tomography/computed tomography in the detection of metastatic bladder cancer

Objectives: To investigate the value of whole‐body fluorine‐18 2‐fluoro‐2‐deoxy‐D‐glucose positron emission tomography/computed tomography for the detection of metastatic bladder cancer. Methods: From December 2006 to August 2010, 60 bladder cancer patients (median age 60.5 years old, range 32–96) underwent whole body positron emission tomography/computed tomography positron emission tomography/computed tomography. The diagnostic accuracy was assessed by performing both organ‐based and patient‐based analyses. Identified lesions were further studied by biopsy or clinically followed for at least 6 months. Results: One hundred and thirty‐four suspicious lesions were identified. Among them, 4 primary cancers (2 pancreatic cancers, 1 colonic and 1 nasopharyngeal cancer) were incidentally detected, and the patients could be treated on time. For the remaining 130 lesions, positron emission tomography/computed tomography detected 118 true positive lesions (sensitivity = 95.9%). On the patient‐based analysis, the overall sensitivity and specificity resulted to be 87.1% and 89.7%, respectively. There was no difference of sensitivity and specificity in patients with or without adjuvant treatment in terms of detection of metastatic sites by positron emission tomography/computed tomography. Compared with conventional imaging modality, positron emission tomography/computed tomography correctly changed the management in 15 patients (25.0%). Conclusions: Positron emission tomography/computed tomography has excellent sensitivity and specificity in the detection of metastatic bladder cancer and it provides additional diagnostic information compared to standard imaging techniques.     

Positron Emission Tomography in Clinical Islet Transplantation

The fate of islets in clinical transplantation is unclear. To elude on this positron emission tomography combined with computed tomography (PET/CT) was performed for 60 min during islet transplantation in five patients receiving six transplants. A fraction of the islets (23%) were labeled with 18F‐fluorodeoxyglucose ([¹⁸F]FDG) and carefully mixed with unlabeled islets just prior to intraportal transplantation. The peak radioactivity concentration in the liver was found at 19 min after start of islet infusion and corresponded to only 75% of what was expected, indicating that islets are lost during the transplantation procedure. No accumulation of radioactivity was found in the lungs. A nonphysiological peak of C‐peptide was found in plasma during and immediately after transplantation in all subjects. Distribution in the liver was heterogeneous with wide variations in location and concentration. Islets found in areas with concentrations of >400 IEQ/cc liver tissue varied between 1% and 32% of the graft in different subjects. No side effects attributed to the PET/CT procedure were found. Clinical outcome in all patients was comparable to that previously observed indicating that the [¹⁸F]FDG labeling procedure did not harm the islets. The technique has potential to be used to assess approaches to enhance islet survival and engraftment in clinical transplantation.     

18F‐FDG‐PET/CT predicts early tumor recurrence in living donor liver transplantation for hepatocellular carcinoma

The prognosis including ¹⁸F‐fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F‐FDG‐PET/CT) for the early recurrence for hepatocellular carcinoma (HCC) after living donor liver transplantation (LDLT) was not well established. Consecutive patients who underwent ¹⁸F‐FDG‐PET/CT and subsequent LDLT for HCC from March 2005 to June 2011 were enrolled. The 191 patients with a median follow‐up of 26.1 months were evaluated. There were 20 patients (10.5%) with early recurrence (≤6 months), 18 patients (9.4%) with late recurrence (>6 months), and 153 patients (80.1%) with no recurrence. Fifty‐five patients (28.8%) displayed increased PET/CT tumor uptake. Three‐year overall and disease‐free survival for PET/CT‐positive patients were 65.5% and 57.1%, respectively, while PET/CT‐negative patients showed respective values of 89.8% and 86.8% (P = 0.001 vs. P < 0.001). Tumor variables associated with PET/CT‐positive finding were preoperative AFP level, Milan, UCSF criteria, maximum tumor size, total tumor size, differentiation, vascular invasion, and serosal invasion. PET/CT‐positive status was identified as an independent prognostic factor for disease‐free survival influencing early recurrence in multivariable analysis (HR 3.945, 95% CI 1.196–13.016, P = 0.024). ¹⁸F‐FDG‐PET/CT is an independent and significant predictor of early tumor recurrence in LDLT for HCC.     

18F-FDG PET/CT in pancreatic adenocarcinoma: A role at initial imaging staging?

Pancreatic ductal adenocarcinoma represents 90% of all pancreatic tumors. The only hope for prolonged survival in patients with this condition still remains surgery with complete R0 resection. Initial imaging has a pivotal role to identify patients who are eligible to curative surgery and those who may benefit of neoadjuvant chemotherapy. This review provides an analysis of the recent literature on 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in pancreatic adenocarcinoma. Performances of FDG PET in the detection of lymph node involvement and metastatic spread at initial staging and those in the assessment of response to treatment are described.