Multiple myeloma (MM) is a hematologic malignancy associated with uncontrolled clonal proliferation of plasma cells. Extramedullary disease in MM is an aggressive entity with a poor prognosis. Moreover, involvement of the gastrointestinal tract is a rare aggressive biological sign. ¹⁸F-FDG PET/CT is an irreplaceable modality in the assessment of extramedullary disease. We present 2 cases with gastric involvement of MM that were shown by ¹⁸F-FDG PET/CT and confirmed as plasma cell infiltration pathologically. ¹⁸F-FDG PET/CT studies of MM patients should be interpreted carefully for gastrointestinal involvement, and it should be kept in mind that it can mimic other malignancies.

Background/aim: The aim of our study was to evaluate the effect of reduced injected tracer activities on the quantitative image metrics and the visual image quality in whole-body 18F-FDG PET/MRI with TOF capability in pediatric oncology. Materials and methods: Seventy-seven PET/MRI examinations of 54 patients were analyzed (standard injected activity: 1.9 MBq/kg, standard PET scan duration: 5 min per bed position). Lower activity PET images (1.2 MBq/kg and 0.9 MBq/kg) were retrospectively simulated from the originally acquired list-mode data sets. Quantitative parameters were assessed by measuring the SUV metrics, signal-to-noise ratio (SNR), contrast-to-noise ratios (CNR), and textural features in each PET data set. PET images were also evaluated visually for image quality by using a scoring system. Results: SNRs were found as significantly different among PET data sets (p < 0.001) and showed increasing image noise with decreasing activities. CNR values did not show significant differences among PET data sets. The mean relative percentage changes in SUV metrics were found to be lower in 1.2 MBq/kg data set compared to 0.9 MBq/kg data set. Lesion SUVmax, SUVmean, SULpeak, and textural features were significantly different in 0.9 MBq/kg data set compared to the original data set (p < 0.05 for all). However, SUV metrics and textural features did not show a significant difference between the original and 1.2 MBq/kg data sets. While, the mean visual scores in 0.9 MBq/kg data set were significantly different compared to the original data set (p < 0.001), there was no significant difference between the original and 1.2 MBq/kg data sets in terms of general image quality and image sharpness. Conclusion: Our analyses showed that the reduction of injected activity to 1.2 MBq/kg may be feasible in pediatric oncological PET/ MRI, with a smaller relative percentage change in quantitative parameters and with similar image quality to the original data set.

To investigate the association between vascular inflammation, as detected by positron emission tomography (PET) imaging and interleukin-6 (IL-6), pentraxin3, and B-cell-activating factor (BAFF) in subjects with LVV. The study included newly diagnosed giant cell arteritis (GCA, n = 27) or Takayasu arteritis (n = 9) patients and healthy control (HC, n = 31) subjects. PET scan and blood samples were obtained before the introduction of treatments. IL-6, PTX3, and BAFF levels were determined quantitatively by enzyme-linked immunosorbent assay kits. Thirty-six patients with LVV (20 females, 16 males; age 64.5 ± 16.6 years) and 31 HC (14 females, 17 males; age 37.1 ± 9.6 years) were included. Serum levels of IL-6, PTX3, and BAFF were increased in patients with newly diagnosed LVV compared with healthy control subjects. In receiver operating characteristics (ROC) analysis, serum IL-6 and BAFF provided excellent discrimination of newly diagnosed LVV patients from HC (area under the ROC curve of >0.90 and >0.80, respectively). None of the inflammatory markers correlated with vascular inflammatory activity determined by PET scanning. Our results suggest that IL-6 and BAFF may serve as markers of large vessel vasculitis, while PTX3 is not useful. None of the inflammatory markers correlated with PET assessed vasculitis activity.

Objectives: This retrospective study aimed to evaluate the prognostic importance of F-18-fluorodeoxyglucose (F-18-FDG)-positive pelvic lymph nodes (LNs) and extra -pelvic disease on staging F-18-FDG positron emission tomography/computed tomography (PET/CT) in patients with bladder cancer. Methods: Bladder cancer patients who underwent staging F-18-FDG PET/CT were included in the study. Histopathologic features of tumors, therapy histories, presence of distinguishable tumors on CT and PET images, sizes and maximum standardized uptake value (SUVmax) of primary tumors, total numbers, sizes, and SUVmax of F-18-FDG-positive pelvic and extra -pelvic LNs, and total numbers and SUVmax of distant metastases (M1a/1b) were recorded. Patients were followed up until death or the last medical visit. Factors predicting overall survival were determined using Cox regression analysis. Results: Fifty-five patients [median age: 70 (53-84), 48 (87.3%) male, 7 (12.7%) female] with bladder cancer were included in this study. Twentynine (52.7%) patients had 18F-FDG positive pelvic LNs, while 24 (43.7%) patients had 18F-FDG positive extra -pelvic disease. Patients with F-18-FDG- positive pelvic LNs had a higher rate of extra -pelvic disease (p=0.003). The median follow-up duration was 13.5 months. The median overall survival was 16.3 months [95% confidence interval (CI) 8.9-23.7]. The primary tumor distinguishability on PET (p=0.011) and CT (p=0.009) images, the presence of F-18-FDG-positive pelvic LNs (p<0.001) and F-18-FDG-positive extra -pelvic disease/distant metastases (M1a/M1b) (p<0.001), and the number of distant metastases (p=0.034) were associated with mortality. The F-18-FDG-positive extra -pelvic disease/distant metastases [p=0.029, odds ratio: 4.15 (95% CI 1.16-14.86)] was found to be an independent predictor of mortality in patients with bladder cancer. Conclusion: The presence of 18F-FDG-positive extra -pelvic disease in pretreatment 18F-FDG PET/CT is an important prognostic factor in bladder cancer patients.

Purpose: This study aimed to evaluate the role of primary tumor quantitative parameters obtained from ¹⁸F-FDG PET/MRI in breast cancer (BC) patients in the prediction of pathological complete response (pCR). Methods: Patients with BC who underwent PET/MRI for staging and neoadjuvant treatment (NAT) response evaluation, and underwent surgical resection at the end of the treatment (EOT) were retrospectively reviewed. A total of 59 patients were included in the study. Maximum standard uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG) and minimum apparent diffusion coefficient (ADCmin) value of the primary tumors were obtained from the initial and EOT PET/MRI. The patients were divided into two groups according to PERCIST: those with complete metabolic response (CMR) and those without CMR. The role of quantitative parameters in predicting pCR was evaluated by using decision tree model as a result of classifications in the Rweka package of the R software. Results: pCR was detected in 22 of 59 patients (37.3%). The sensitivity, specificity and accuracy of the evaluation according to PERCIST in predicting pCR were found to be 90.9%, 75.7% and 81.4%, respectively. In the decision tree model, patients were classified using a two-layer model with the values of EOT_ADCmin (cutoff value > 1.6 × 10^− 3 mm²/s, complete response) and EOT_SUVmax (cutoff value > 1.45, incomplete response). According to the confusion matrices, the model correctly classified 56 patients (sensitivity: 95.5%, specificity: 94.6%, accuracy: 94.9%). The accuracy of the model was found to be 93.2% with the usage of 10-fold cross-validation method. Conclusion: In BC patients who received NAT, EOT_ADCmin and EOT_SUVmax were found as predictive factors for pCR. The combined assessment of tumor metabolism and cell density may be useful in non-invasive prediction of pCR, with higher accuracy compared to PERCIST.