Different 18 F-FDG PET parameters for the prediction of histological response to neoadjuvant chemotherapy in pediatric Ewing sarcoma family of tumors.

BACKGROUND: The histological response to neoadjuvant chemotherapy (NAC) in pediatric patients with Ewing sarcoma family of tumors (ESFT) can predict the disease-free survival. Therefore, a noninvasive method for response assessment is needed. Using the currently established imaging modalities, mass reduction does not always correlate with the percentage of necrosis. OBJECTIVE: To determine the potential role of 18 fluorine-labeled fluoro-2-deoxyglucose positron emission tomography (18 F-FDG PET) metabolic parameters in the prediction of poor histological response to NAC in pediatric patients with ESFT. METHODS: Thirty-six patients who were treated with NAC and surgery at the Children's Cancer Hospital, Egypt, were prospectively included in this study. All patients underwent two studies; a PET/CT study before NAC and another one after NAC completion. Metabolic PET parameters were measured in each study. The ability of each of these parameters, their pretreatment and pre-local control values, as well as the percentage reduction between their pretreatment and pre-local control values, were evaluated to differentiate between good and poor responders using the histological response as a standard reference. RESULTS: Neither the pretreatment value nor the percentage reduction of any of the measured PET parameters predicted poor histological response. After NACcompletion, metabolic tumor volume (MTV) at the threshold of an SUV of 2.5 isocontour (MTV(2.5)post ), MTV at the threshold of hepatic reference SUVmean (MTV(HR)post ), and total lesion glycolysis at the threshold of hepatic reference SUVmean (TLG(HR)post ) predicted poor histological response (P  = 0.006, 0.018, and 0.003, respectively). The cutoff values of 90% reduction of TLG(HR) and maximum standardized uptake value (SUVmax)post ≤2.5 could differentiate between good and poor responders. CONCLUSION: FDG PET parameters can predict poor histological response to NAC in ESFT patients. MTV and TLG at the thresholds of an SUV of 2.5 isocontour and hepatic reference SUVmean are the two most promising thresholds in predicting the response of patients. The cutoff value of SUVmaxpost ≤2.5 predicts poor histological response.

Diagnostic Accuracy of Dual-Time-Point Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography in Verification Local Recurrence in Pancreatic Cancer Patients.

PURPOSE: The aim of this study was to evaluate the accuracy of dual-time point in differentiating benign from malignant local recurrent lesions in pancreatic cancer. PATIENTS AND METHODS: Thirty-four patients with pancreatic cancer (22 males and 12 females, mean age: 58.3 ± 10.3) who presented with soft-tissue lesions at the operative bed. Early whole-body positron emission tomography/computed tomography (PET/CT) and delayed imaging on the abdomen were performed. The maximum standardized uptake value (SUVmax) of the initial image (SUVmax E) and the delayed image (SUVmax D) were determined. A Retention Index (RI) was also calculated. These indices were correlated with histopathology and follow-up as reference criteria. RESULTS: No significant statistical difference in SUVmaxE was found between benign and malignant lesions, while SUVmaxD and RI of the malignant lesions (mean 8.6 ± 2.7 and 35.8 ± 18.3, respectively) were significantly higher than those of benign ones (mean 3.3 ± 1.4 and-6.2 ± 15.2, respectively) (P < 0.005). With SUVmaxD 4.9, malignancy could be predicted with the highest sensitivity (95.8%) and accuracy (94.1%) between the whole parameters. The estimated negative and positive predictive values (PPVs) were 90.0% and 95.8%, respectively. A cutoff point 16 for RI showed higher specificity and PPV (100% and 100%, respectively). Forty-seven total (11 benign and 36 malignant) lesions were identified. Increased SUVmax is noted on delayed images in most of malignant lesions, except for two that maintained stationary. CONCLUSION: Dual-time-point 18F fluorodeoxyglucose-PET/CT seems to be a reliable additional method to differentiate between malignant and benign postoperative local soft-tissue lesions in patients with pancreatic cancer.

Added predictive value of 18F-FDG PET/CT for pediatric rhabdomyosarcoma.

OBJECTIVE: To determine the prognostic value of quantitative fluorine-18-fluorodeoxyglucose (F-FDG) standardized uptake value (SUV) in patients with pediatric rhabdomyosarcoma (RMS). PATIENTS AND METHODS: Consecutive 98 (50 males and 48 females) (age range: 4 months to 17.5 years, mean age: 5.8 ± 4.5) patients with pathologically proven RMS who underwent PET/computed tomography for initial staging were retrospectively assessed for whether primary SUVmax and the primary/liver SUVmax ratio could predict event-free survival (EFS) and overall survival (OS) for 36 months using receiver operating characteristic curve analysis. Univariate and multivariate analyses were used to determine the reliability of these metabolic parameters and various clinical factors. RESULTS: Higher SUVmax was significantly related to the presence of regional or distant metastasis with worse prognosis. With receiver operating characteristic curve marked cut-off values of 3.6 and 2.1 for primary SUVmax and the primary/liver SUVmax ratio, respectively, both EFS and OS proved to be higher in patients with SUVmax ranked below the determinate values. Patients with a primary/liver SUVmax ratio below the cut-off value of 2.1 had OS (60.8%) and EFS (48.1%) compared with 44.5 and 14.8% for patients with lesions exceeding the cut-off point of uptake; however, this failed to achieve statistical significance. In the evaluation of primary SUVmax, similar results were obtained with P values of 0.76 and 0.62, respectively. High SUVmax was more prevalent among patients with less favorable clinical and pathological features including unfavorable primary site, alveolar pathology, and high-risk group. CONCLUSION: F-FDG PET/computed tomography may be considered an additional prognostic predictor of outcome in RMS patients, where higher F-FDG uptake seems to be linked to lower survival and correlated to different unfavorable parameters.