Is there a need for dedicated bone imaging in addition to 18F-FDG PET/CT imaging in pediatric sarcoma patients?

Many children with sarcomas undergo whole body 2-deoxy-2-((18)F)fluoro-D-glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) and technetium methylene diphosphonate ((99)Tc-MDP) studies. It is unknown whether the combination of both tests results in more accurate detection of bone lesions than (18)F-FDG- PET/CT alone.

The impact of 18F-FDG PET on the management of patients with suspected large vessel vasculitis

We aimed to assess the impact of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) on the management of patients with suspected large vessel vasculitis.

Hypodense regions in unenhanced CT identify nonviable myocardium: validation versus 18F-FDG PET

The aim of the present study was to evaluate the accuracy of hypodense regions in non-contrast-enhanced cardiac computed tomography (unenhanced CT) to identify nonviable myocardial scar tissue.

18F-fluorodeoxyglucose uptake of bone and soft tissue sarcomas in pediatric patients

A high (18)F-fluorodeoxyglucose (FDG) uptake by positron emission tomography/computed tomography (PET/CT) imaging in sarcomas of adults has been reported. The current study aimed at defining the degree of (18)F-FDG uptake of pediatric sarcomas. This retrospective study included 29 patients (23 males, 6 females; mean age 14 ± 5 years) with soft tissue (n = 9) or bone (n = 20) sarcomas. Twenty-two patients (76%) underwent (18)F-FDG PET/CT and 7 (24%) had dedicated (18)F-FDG PET studies. Tumor (18)F-FDG uptake was quantified by standard uptake value (SUV)(max) and tumor-to-liver ratios (SUV ratios; tumor SUV(max)/liver SUV(mean)). Tumor SUV(max) and SUV ratios were correlated with tumor Ki-67 expression. SUV(max) ranged from 1.4 to 24 g/mL (median 2.5 g/mL) in soft tissue sarcomas and 1.6 to 20.4 g/mL (median 6.9 g/mL) in bone sarcomas (P = .03), and from 1.6 to 9.2 g/mL (median 3.9 g/mL) and 3.5 to 20.4 g/mL (median 12 g/mL) in Ewing sarcoma and osteosarcoma, respectively (P = .009). Tumor SUV ratios ranged from 0.8 to 8.7 (median 1.9) in soft tissue sarcomas and 1.4 to 8.9 (median 3.8) in bone sarcomas (P = .08). Ewing sarcoma had a significantly lower tumor SUV ratio than osteosarcoma (P = .01). Ki-67 expression correlated significantly with the (18)F-FDG uptake in bone but not in soft tissue sarcomas. All sarcomas were visualized by (18)F-FDG PET/CT imaging. A higher (18)F-FDG uptake was observed in osteosarcoma than in Ewing and soft tissue sarcomas. The results of this study suggest that the degree of tumor (18)F-FDG uptake is sufficient to allow for monitoring of therapeutic responses in pediatric sarcomas.

18F-RB390: innovative ligand for imaging the T877A androgen receptor mutant in prostate cancer via positron emission tomography (PET).

BACKGROUND Detecting prostate cancer before spreading or predicting a favorable therapy are challenging issues for impacting patient's survival. Presently, 2-[(18) F]-fluoro-2-deoxy-D-glucose ((18) F-FDG) and/or (18) F-fluorocholine ((18) F-FCH) are the generally used PET-tracers in oncology yet do not emphasize the T877A androgen receptor (AR) mutation being exclusively present in cancerous tissue and escaping androgen deprivation treatment. METHODS We designed and synthesized fluorinated 5α-dihydrotestosterone (DHT) derivatives to target T877A-AR. We performed binding assays to select suitable candidates using COS-7 cells transfected with wild-type or T877A AR (WT-AR, T877A-AR) expressing plasmids and investigated cellular uptake of candidate (18) F-RB390. Stability, biodistribution analyses and PET-Imaging were assessed by injecting (18) F-RB390 (10MBq), with and without co-injection of an excess of unlabeled DHT in C4-2 and PC-3 tumor bearing male SCID mice (n = 12). RESULTS RB390 presented a higher relative binding affinity (RBA) (28.1%, IC50  = 32 nM) for T877A-AR than for WT-AR (1.7%, IC50  = 357 nM) related to DHT (RBA = 100%). A small fraction of (18) F-RB390 was metabolized when incubated with murine liver homogenate or human blood for 3 hr. The metabolite of RB390, 3-hydroxysteroid RB448, presented similar binding characteristics as RB390. (18) F-RB390 but not (18) F-FDG or (18) F-FCH accumulated 2.5× more in COS-7 cells transfected with pSG5AR-T877A than with control plasmid. Accumulation was reduced with an excess of DHT. PET/CT imaging and biodistribution studies revealed a significantly higher uptake of (18) F-RB390 in T877A mutation positive xenografts compared to PC-3 control tumors. This effect was blunted with DHT. CONCLUSION Given the differential binding capacity and the favorable radioactivity pattern, (18) F-RB390 represents the portrayal of the first imaging ligand with predictive potential for mutant T877A-AR in prostate cancer for guiding therapy. Prostate 75:348-359, 2015. © 2014 Wiley Periodicals, Inc.

Serial [18F]-fluoromisonidazole PET during radiochemotherapy for locally advanced head and neck cancer and its correlation with outcome.

PURPOSE The aim was to assess changes of tumour hypoxia during primary radiochemotherapy (RCT) for head and neck cancer (HNC) and to evaluate their relationship with treatment outcome. MATERIAL AND METHODS Hypoxia was assessed by FMISO-PET in weeks 0, 2 and 5 of RCT. The tumour volume (TV) was determined using FDG-PET/MRI/CT co-registered images. The level of hypoxia was quantified on FMISO-PET as TBRmax (SUVmaxTV/SUVmean background). The hypoxic subvolume (HSV) was defined as TV that showed FMISO uptake ⩾1.4 times blood pool activity. RESULTS Sixteen consecutive patients (T3-4, N+, M0) were included (mean follow-up 31, median 44months). Mean TBRmax decreased significantly (p<0.05) from 1.94 to 1.57 (week 2) and 1.27 (week 5). Mean HSV in week 2 and week 5 (HSV2=5.8ml, HSV3=0.3ml) were significantly (p<0.05) smaller than at baseline (HSV1=15.8ml). Kaplan-Meier plots of local recurrence free survival stratified at the median TBRmax showed superior local control for less hypoxic tumours, the difference being significant at baseline and after 2weeks (p=0.031, p=0.016). CONCLUSIONS FMISO-PET documented that in most HNC reoxygenation starts early during RCT and is correlated with better outcome.

In vitro and in vivo characterization of novel 18F-labeled bombesin analogues for targeting GRPR-positive tumors

The gastrin-releasing peptide receptor (GRPR) is overexpressed on a number of human tumors and has been targeted with radiolabeled bombesin analogues for the diagnosis and therapy of these cancers. Seven bombesin analogues containing various linkers and peptide sequences were designed, synthesized, radiolabeled with (18)F, and characterized in vitro and in vivo as potential PET imaging agents. Binding studies displayed nanomolar binding affinities toward human GRPR for all synthesized bombesin analogues. Two high-affinity peptide candidates 6b (K(i) = 0.7 nM) and 7b (K(i) = 0.1 nM) were chosen for further in vivo evaluation. Both tracers revealed specific uptake in GRPR-expressing PC-3 tumors and the pancreas. Compared to [(18)F]6b, compound [(18)F]7b was characterized by superior tumor uptake, higher specificity of tracer uptake, and more favorable tumor-to-nontarget ratios. In vivo PET imaging allowed for the visualization of PC-3 tumor in nude mice suggesting that [(18)F]7b is a promising PET tracer candidate for the diagnosis of GRPR-positive tumors in humans.

Correlation of 6-18F-fluoro-L-dopa PET uptake with proliferation and tumor grade in newly diagnosed and recurrent gliomas

6-(18)F-fluoro-l-dopa ((18)F-FDOPA) measured with PET as a biomarker of amino acid uptake has been investigated in brain tumor imaging. The aims of the current study were to determine whether the degree of (18)F-FDOPA uptake in brain tumors predicted tumor grade and was associated with tumor proliferative activity in newly diagnosed and recurrent gliomas.

Comparison of FDG-PET/CT and bone scintigraphy for detection of bone metastases in breast cancer

Bone scintigraphy is the standard procedure for the detection of bone metastases in breast cancer patients. FDG-PET/CT has been reported to be a sensitive tool for tumor staging in different malignant diseases. However, its accuracy for the detection of bone metastases has not been compared to bone scintigraphy.

Impact of 3,4-dihydroxy-6-18F-fluoro-L-phenylalanine PET/CT on managing patients with brain tumors: the referring physician's perspective

We investigated the impact of (18)F-DOPA brain PET/CT on the clinical management of patients with known or suspected brain tumors.