Synthesis, Quality Control, and Bench-to-Bed Translation of a New [68Ga]Ga-Labeled NOTA-Conjugated Bisphosphonate for Imaging Skeletal Metastases by Positron Emission Tomography.

Background: Early detection of skeletal metastasis is of great interest to determine the prognosis of cancer. Positron emission tomography-computed tomography (PET-CT) imaging provides a better temporal and spectral resolution than single photon emission computed tomography-computed tomography (SPECT-CT) imaging, and hence is more suitable to detect small metastatic lesions. Although [18F]NaF has been approved by U.S. FDA for a similar purpose, requirement of a medical cyclotron for its regular formulation restricts its extensive utilization. Efforts have been made to find suitable alternative molecules that can be labeled with 68Ga and used in PET-CT imaging. Objective: The main objective of this study is to synthesize and evaluate a new [68Ga]Ga-labeled NOTA-conjugated geminal bisphosphonate for its potential use in early detection of skeletal metastases using PET-CT. Methods: The authors performed a multistep synthesis of a new NOTA-conjugated bisphosphonic acid using thiourea linker and radiolabeled the molecule with 68Ga. The radiolabeled formulation was evaluated for its in vitro stability, affinity for hydroxyapatite (HA) particles, preclinical biodistribution in animal models, and PET-CT imaging in patients. Results: The bifunctional chelator (NOTA)-conjugated bisphosphonate was synthesized with 97.8% purity and radiolabeled with 68Ga in high yield (>98%). The radiolabeled formulation was found to retain its stability in vitro to the extent of >95% up to 4 h in physiological saline and human serum. The formulation also showed high affinity for HA particles in vitro with Kd = 907 ± 14 mL/g. Preclinical biodistribution studies in normal Wistar rats demonstrated rapid and almost exclusive skeletal accumulation of the complex. PET-CT imaging in a patient confirmed its ability to detect small metastatic skeletal lesions. Conclusions: The newly synthesized [68Ga]Ga-labeled NOTA-conjugated bisphosphonate is a promising radiotracer for PET-CT imaging for skeletal metastases.

A cost effective method for the preparation of sodium fluoride [18F]NaF for PET-CT imaging by using an in-house designed module.

We report the development of a manual module for the preparation of [18F]NaF for metastatic bone cancer imaging. By using this simple module, [18F]NaF production can be carried out inexpensively without using commercially available kits. The module can be used for making [18F]NaF from freshly irradiated H218O water or with left over activity in the target after [18F]FDG production. The product meets all quality control parameters.

Gallium 68-PSMA PET/CT for lesion characterization in suspected cases of prostate carcinoma.

OBJECTIVE: To assess the feasibility of gallium 68 (Ga)-prostate specific membrane antigen (PSMA) PET/computed tomography (CT) to identify patients who truly harbor clinically significant prostate cancer (PCa) in a cohort of patients with clinical and biochemical/radiological suspicion of PCa. PATIENTS AND METHODS: A total of 118 patients with suspected PCa who underwent Ga-PSMA PET/CT between May 2015 and June 2016 were prospectively included. Final decision on performing biopsy was left to the referring urologist after considering the clinical data, scan findings and discussion with the patient. RESULTS: Overall, 51 patients were scan negative, among whom six underwent biopsy but was negative for malignancy. In 45 patients, an immediate biopsy could be avoided and put on follow-up. None of these patients were documented to have PCa in the short average follow-up of 6 months. Among 67 patients who were scan positive, 56 patients underwent transrectal ultrasonography-guided biopsy, and malignancy could be documented in 46 of them. In addition, comprehensive initial staging information could be obtained in them, with organ-confined disease demonstrated in 33 patients and metastatic disease in 13 patients. CONCLUSION: Ga-PSMA PET/CT can act as a gate keeper in selecting patients with suspected PCa who should undergo an immediate transrectal ultrasonography-guided biopsy and who could be kept on active surveillance.

Utility of 68Ga-PSMA-11 PET/CT in Imaging of Glioma-A Pilot Study.

BACKGROUND: Imaging of gliomas remains challenging. The aim of the study was to assess the feasibility of using Ga-PSMA-11 PET/CT for imaging gliomas. METHODS: Fifteen patients with glioma from 2 centers were included in the study. Ten patients were treated cases of glioblastoma with suspected recurrence. Two patients were sent for assessing the nature (primary lesion/metastasis) of space-occupying lesion in the brain; 3 patients were imaged immediately after surgery and before radiotherapy. Target-to-background ratios (TBR) for the brain lesions were calculated using contralateral cerebellar uptake as background. RESULTS: Among the 10 cases with suspected recurrence, scan was positive in 9, subsequent surgery was done, and histopathology proved it to be true recurrence. In the scan-negative case on follow-up, no evidence of disease could be made clinically or radiologically. Among the other cases the presence or absence of disease could be unequivocally identified on the Ga-PSMA-11 brain scan and correlated with the histopathology or other imaging. Apart from the visual assessment quantitative assessment of the lesions with TBR also showed a significantly high TBR value for those with true disease compared with those with no disease. CONCLUSIONS: In the evaluation of gliomas, Ga-PSMA-11 PET/CT brain imaging is a potentially useful imaging tool. The use of Ga-PSMA-11 brain PET/CT in evaluation of recurrent glioma seems promising. Absence of physiological uptake of Ga-PSMA-11 in the normal brain parenchyma results in high TBR values and consequently better visualization of glioma lesions.

Rare Case of Intratracheal Metastasis Detected on 68Ga-Prostate-Specific Membrane Antigen PET/CT Scan in a Case of Thyroglobulin Elevated Negative Iodine Scan Syndrome.

A 64-year-old woman underwent completion thyroidectomy with upper tracheal ring resection and right-sided neck dissection for papillary carcinoma of the thyroid infiltrating the trachea and was given I radioiodine treatment. Three years later, she presented with hemoptysis. On evaluation, she had increased serum thyroglobulin and negative iodine scan (TENIS). F-FDG PET/CT scan did not identify any site of disease. One year later, Ga-PSMA scan done revealed a moderate focal tracer-avid intratracheal soft tissue; biopsy revealed it to be metastatic papillary carcinoma of the thyroid. This case kindles the possibility of using Ga-PSMA PET/CT to reveal occult disease in cases of TENIS.

68Ga-PSMA Uptake in an Incidentally Detected Gastrointestinal Stromal Tumor in a Case of Suspected Carcinoma Prostate.

A 74-year-old man with suspected prostate cancer and a previously negative transrectal ultrasound-guided prostate biopsy underwent Ga-PSMA PET/CT. Scan showed no abnormal tracer concentration in enlarged prostate gland to suggest prostate cancer. Note was made of an incidentally detected well defined soft tissue lesion in the greater curvature of the stomach with moderate tracer concentration in its intraluminal portion. Biopsy of the lesion revealed gastrointestinal stromal tumor.

False Positive Uptake in Bilateral Gynecomastia on 68Ga-PSMA PET/CT Scan.

A 66-year-old man on hormonal therapy with prostate cancer was referred for Ga-PSMA PET/CT scan for biochemical recurrence. Ga-PSMA PET/CT scan detected moderate heterogeneous tracer concentration in bilateral breast parenchyma, in addition to the abnormal tracer concentration in enlarged prostate gland, right external iliac lymph node, and sclerotic lesion in L4 vertebra. On clinical examination, he was found to have bilateral gynecomastia. Abnormal concentration of Ga-PSMA in breast cancer is now well known, and in this context, it is important to know that tracer localization can occur in gynecomastia as well, as evidenced in this case.

18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Scan in an Unusual Case of Lymphoma with Secondary Involvement of Uterine Cervix Presenting as a Pathological Fracture.

A 48-year-old female presented with a pathological fracture of the right femur. 99mTc methylene diphosphonate bone scan revealed multiple areas of increased osteoblastic activity consistent with metastatic disease. Serum electrophoresis revealed monoclonal gammopathy. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan revealed metabolically active lesions in bulky uterine cervix and osteolytic skeletal lesions. Unusual pattern of FDG uptake in uterine cervix and osteolytic skeletal lesions warranted a biopsy of the uterine cervix which revealed diffuse large B-cell lymphoma. 18F-FDG PET/CT scan helped in guiding the site of biopsy to reach a final diagnosis in this unusual case of lymphoma with a secondary involvement of uterine cervix presenting as a pathological fracture.

68Ga-PSMA PET/CT in Osteosarcoma in Fibrous Dysplasia.

Fibrous dysplasia (FD) is a benign bone lesion with a rare but potential for malignant transformation. Neither Tc-MDP nor F-FDG PET/CT can differentiate between FD and areas of malignant transformation in FD. We described a case of osteosarcoma developing in FD with selective uptake of tracer in malignant transformation areas demonstrated on a Ga-PSMA PET/CT scan. Our case highlights the ability of Ga-PSMA PET/CT to map tumor neoangiogenesis in osteosarcoma arising in FD, which can have potential implications in prognostication, possibility of antiangiogenesis-based therapeutic options, and in response assessment following chemotherapy.

68Ga PSMA PET/CT in a Rare Case of Metastatic Adenocarcinoma Prostate Presenting as Numb Chin Syndrome.

A 68-year-old man presented with right-side facial numbness. MRI showed an extra-axial mass infiltrating the right temporal bone. It was debulked surgically, and histopathology revealed metastatic adenocarcinoma. Ga PSMA PET/CT done in view of increased PSA levels and clinically suspicious hard lesion in prostate showed primary lesion in left side of prostate with metastases to the right temporal bone. Primary carcinoma of the prostate and metastases to the right temporal bone were proven histopathologically. Our case highlights the usefulness of Ga PSMA PET/CT in identifying the primary site in suspected prostate cancer and mapping the metastatic sites.

68Ga-PSMA PET/CT Imaging in Multiple Myeloma.

The potential applications of Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT in the imaging of prostate cancer are now well established. A few case reports regarding the potential use of Ga-PSMA PET/CT in nonprostate cancer malignancies are also published. Apparently, the tumor neoangiogenesis is the mechanism attributed to increased Ga-PSMA uptake in the tumor sites in nonprostatic malignancies. We describe the use of Ga-PSMA PET/CT in imaging multiple myeloma. The intense Ga-PSMA avidity of the lesions also opens up the possibility of theranostics with Lu-PSMA.

68Ga-DOTA Ubiquicidin PET/CT in an Infected Implant.

We describe the case of a 55-year-old man who presented with history of fever for 3 months that began 2 months after he had undergone open reduction and internal fixation of left humerus fracture. Implant infection was suspected, but conventional imaging remained unyielding. Ga-DOTA ubiquicidin PET/CT showed increased tracer uptake along the entire length of the implant in the left humerus. Implant removal and temporary external fixation were done. In 24 hours, the patient became afebrile, and blood culture on the fourth day was sterile.

Diagnostic Value of 68Ga PSMA-11 PET/CT Imaging of Brain Tumors-Preliminary Analysis.

OBJECTIVE: To evaluate the feasibility of using Ga PSMA-11 PET/CT for imaging brain lesions and its comparison with F-FDG. METHODS: Ten patients with brain lesions were included in the study. Five patients were treated cases of glioblastoma with suspected recurrence. F-FDG and Ga PSMA-11 brain scans were done for these patients. Five patients were sent for assessing the nature (primary lesion/metastasis) of space occupying lesion in brain. They underwent whole body F-FDG PET/CT scan and a primary site elsewhere in the body was ruled out. Subsequently they underwent Ga PSMA-11 brain PET/CT imaging. Target to background ratios (TBR) for the brain lesions were calculated using contralateral cerebellar uptake as background. RESULTS: In five treated cases of glioblastoma with suspected recurrence the findings of Ga PSMA-11 PET/CT showed good correlation with that of F-FDG PET/CT scan. Compared to the F-FDG, Ga PSMA-11 PET/CT showed better visualization of the recurrent lesion (presence/absence) owing to its significantly high TBR. Among the five cases evaluated for lesion characterization glioma and atypical meningioma patients showed higher SUVmax in the lesion with Ga PSMA-11 than with F-FDG and converse in cases of lymphoma. TBR was better with Ga PSMA PET/CT in all cases. CONCLUSION: Ga PSMA-11 PET/CT brain imaging is a potentially useful imaging tool in the evaluation of brain lesions. Absence of physiological uptake of Ga PSMA-11 in the normal brain parenchyma results in high TBR values and consequently better visualization of metabolically active disease in brain.

Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in a rare case of carcinoma stomach with concomitant silicosis.

The role of fluorine-18 fluorodeoxyglucose. (18F-FDG) positron emission tomography. (PET)/computed tomography. (CT) in the initial staging of various malignancies is now well established. However, nonspecificity of FDG occasionally results in tracer uptake in benign lung lesions. The authors describe a complicated case of carcinoma stomach with multiple nodules and a cavitary lesion in lungs where 18F-FDG PET CT done for initial staging revealed FDG avid mass in stomach, FDG avid multiple mediastinal lymph nodes and multiple intensely FDG avid bilateral lung lesions. The FDG avid lung lesions turned out to be due to silicosis as confirmed by histopathology.

Complimentary Pattern of Uptake in 18F-FDG PET/CT and 68Ga-Prostate-Specific Membrane Antigen PET/CT in a Case of Metastatic Clear Cell Renal Carcinoma.

We describe a case of metastatic clear cell renal cell carcinoma with intensely tracer concentrating lesions in left suprarenal region, mediastinal lymph nodes, lytic bone lesions, thyroid nodules, and mild abnormal tracer-avid lung nodules in Ga-prostate-specific membrane antigen (PSMA) PET/CT. On the other hand F-FDG PET/CT showed mild to no significant abnormal uptake in these lesions. Complimentary uptake pattern was observed in Ga-PSMA and F-FDG PET images in thyroid lesions and D5 vertebral lesion. This case highlights the possibilities of imaging clear cell renal cell carcinoma with Ga-PSMA and opens the possibility of treatment with Lu-PSMA.

Radiolabeled enzyme inhibitors and binding agents targeting PSMA: Effective theranostic tools for imaging and therapy of prostate cancer.

Because of the broad incidence, morbidity and mortality associated with prostate-derived cancer, the development of more effective new technologies continues to be an important goal for the accurate detection and treatment of localized prostate cancer, lymphatic involvement and metastases. Prostate-specific membrane antigen (PSMA; Glycoprotein II) is expressed in high levels on prostate-derived cells and is an important target for visualization and treatment of prostate cancer. Radiolabeled peptide targeting technologies have rapidly evolved over the last decade and have focused on the successful development of radiolabeled small molecules that act as inhibitors to the binding of the N-acetyl-l-aspartyl-l-glutamate (NAAG) substrate to the PSMA molecule. A number of radiolabeled PSMA inhibitors have been described in the literature and labeled with SPECT, PET and therapeutic radionuclides. Clinical studies with these agents have demonstrated the improved potential of PSMA-targeted PET imaging agents to detect metastatic prostate cancer in comparison with conventional imaging technologies. Although many of these agents have been evaluated in humans, by far the most extensive clinical literature has described use of the 68Ga and 177Lu agents. This review describes the design and development of these agents, with a focus on the broad clinical introduction of PSMA targeting motifs labeled with 68Ga for PET-CT imaging and 177Lu for therapy. In particular, because of availability from the long-lived 68Ge (T1/2=270days)/68Ga (T1/2=68min) generator system and increasing availability of PET-CT, the 68Ga-labeled PSMA targeted agent is receiving widespread interest and is one of the fastest growing radiopharmaceuticals for PET-CT imaging.

68Ga-PSMA PET/CT False-Positive Tracer Uptake in Paget Disease.

65-year-old man with left-sided pelvic pain on evaluation was found to have features suggestive of either Paget disease or prostatic bone metastasis of the left hemipelvis based on Tc-MDP bone scan and MRI. Ga-PSMA PET/CT to assess the possibility of primary prostate cancer and if present to stage it helped to rule out prostate cancer because of absence of focal abnormal increased tracer uptake in the prostate gland. However, false-positive tracer uptake was noted in the left hemipelvis, which was subject to biopsy and histopathologically proven to be Paget disease involvement.

Preparation of [(68)Ga]PSMA-11 for PET-CT imaging using a manual synthesis module and organic matrix based (68)Ge/(68)Ga generator.

INTRODUCTION: [(68)Ga]PSMA-11 is a relatively recently introduced radiopharmaceutical for PET-CT imaging of prostate cancer patients. The availability of (68)Ge/(68)Ga generator and PSMA-11 ligand from commercial sources is facilitating the production of the radiopharmaceutical in-house. This paper describes our experience on the preparation of ~200 batches of [(68)Ga]PSMA-11 for conducting PET-CT imaging in patients suspected/suffering from prostate cancer. METHODS: The radiosynthesis of [(68)Ga]PSMA-11 was done in a hospital based nuclear medicine department using (68)Ge/(68)Ga generator and a manual synthesis module, both supplied by Isotope Technologies Garching (ITG), Germany. The production involved the reaction of 5µg (5.3nmol) of PSMA-11 ligand in 1 ml of 0.25M sodium acetate buffer with 4ml of (68)GaCl3 in 0.05M HCl for 5min at 105°C; followed by purification in a C18 cartridge and collection through a 0.22µm pore size filter. RESULTS: The radiochemical yields obtained were consistently high, 93.19%±3.76%, and there was hardly any batch failure. The radiochemical purity of the product was >99% and the product was stable for over 2h; however it was used in patients immediately after preparation. About 200 batches of [(68)Ga]PSMA-11 were prepared during the period and more than 300 patients received the tracer during the 14months of study. No adverse reaction was observed in any of the patients and the image qualities were consistent with literature reports. CONCLUSION: [(68)Ga]PSMA-11 with high radiochemical and radionuclidic purity is conveniently prepared by using a (68)Ge/(68)Ga generator and manual synthesis module. The radiochemical yields are very high; and activity sufficient for 3-4 patients can be prepared in a single batch; multiple batches can be done on the same day and when needed after a gap of 1.5-2h.