Omar Alonso

Evaluation of 99mTc-glucarate as a breast cancer imaging agent in a xenograft animal model.

INTRODUCTION The use of [(99m)Tc]glucarate has been reported as an infarct-avid agent with the potential for very early detection of myocardial infarction. [(99m)Tc]Glucarate has also been postulated as an agent for non-invasive detection of tumors. The aim of our study was to develop a Glucarate kit and evaluate [(99m)Tc]glucarate as a potential cancer imaging agent in female SCID mice bearing human MDA-MB-435 breast tumors. METHODS Glucarate in a kit formulation was labeled with (99m)Tc and evaluated for radiolabelling efficiency and radiochemical purity. The Glucarate kit stability was assessed by monthly quality controls. The pharmacokinetics of [(99m)Tc]glucarate were determined in female SCID mice bearing MDA-MB-435 human breast carcinoma tumors at 0.5, 1, 2, 4 and 24 h. Nuclear imaging studies were performed with a micro-single photon emission tomography (SPECT)/computed tomography (CT) system at 2 h post injection, while magnetic resonance imaging (MRI) was employed for tumor morphology analysis and metastatic deposit localization. RESULTS The Glucarate kits exhibited a stable shelf life of 6 months. [(99m)Tc]Glucarate was obtained with radiochemical purity greater than 95%. Biodistribution studies demonstrated moderate tumor uptake coupled with high renal clearance. Tumor-to-muscle ratios were 4.85 and 5.14 at 1 and 4 h post injection. MRI analysis showed tumors with dense cellular growth and moderate central necrosis. [(99m)Tc]Glucarate uptake in the primary MDA-MB-435 shoulder tumors and metastatic lesions were clearly visualized with micro-SPECT/CT imaging. CONCLUSIONS Selective tumor uptake and rapid clearance from nontarget organs makes [(99m)Tc]glucarate a potential agent for breast cancer imaging that awaits validation in a clinical trial.

[99mTc(CO)3]-Radiolabeled Bevacizumab: In vitro and in vivo Evaluation in a Melanoma Model

Introduction: Vascular endothelial growth factor (VEGF) is one of the classic factors to tumor-induced angiogenesis in several tumor types, including melanoma. Bevacizumab, a monoclonal antibody against VEGF, could be used as an imaging tool in preclinical studies. Objective: To radiolabel bevacizumab with [^99mTc(CO)₃(OH₂)₃]⁺ and evaluate it in vivo and in vitro for melanoma imaging properties. Methods: Bevacizumab was radiolabeled with [^99mTc(CO)₃(OH₂)₃]⁺ ion in saline. The radiochemical stability of the labeled antibody was assessed. The biodistribution and scintigraphy imaging of the radiolabeled antibody were evaluated in normal C57BL/6J mice and in C57BL/6J mice bearing murine B16F1 melanoma tumors. Immunoreactivity of bevacizumab to murine tumors was determined from direct immunofluorescence and immunoblotting assays. Results: We demonstrate that ^99mTc(CO)₃-bevacizumab was stable. In vivo biodistribution studies revealed that tumor uptake of ^99mTc(CO)₃-bevacizumab was 2.64 and 2.51 %ID/g at 4 and 24 h postinjection. Scintigraphy image studies showed tumor selective uptake of ^99mTc(CO)₃-bevacizumab in the tumor-bearing mice. This affinity was confirmed by immunoassays performed on B16F10 tumor samples. Conclusions:^99mTc(CO)₃-bevacizumab could be used as an approach for tumor nuclear imaging in preclinical studies. This should be useful to provide insights into the angiogenic stimulus before and after chemotherapy, which might help improve current antitumor therapy.

Development of 99mTc(CO)3-dendrimer-FITC for cancer imaging

Study of fluorophore and technetium labeling of poly(amido)-amine (PAMAM) generation 4 (G4) dendrimer and its evaluation as potential molecular imaging agent in both normal and melanoma-bearing mice, are described. Dendrimers were first conjugated with FITC (fluorescein isothiocyanate). Dendrimer-FITC was then incubated with the intermediate [(99m)Tc(CO)(3)(H(2)O)(3)](+) and purified by gel filtration. Biodistribution and scintigraphy images were performed administrating (99m)Tc(CO)(3)-dendrimer-FITC to normal mice (NM) or melanoma-bearing mice (MBM). Cryostat tissue sections from MBM mice were analyzed by confocal microscopy. Radiolabeling yield of dendrimer was approx. 90%. The (99m)Tc(CO)(3)-dendrimer-FITC complex was stable for at least 24h. Biodistribution studies in NM showed blood clearance with hepatic and renal depuration. MBM showed a similar pattern of biodistribution with high tumor uptake that allowed tumor imaging. Confocal microscopy analysis showed cytoplasmic distribution of (99m)Tc(CO)(3)-dendrimer-FITC.

99mTc-HYNIC octreotide in neuroblastoma

Disease status assessment of neuroblastoma patients requires computed tomography (or magnetic resonance imaging), bone scan, metaiodobenzylguanidine (MIBG) scan, bone marrow tests, and urine catecholamine measurements. There is no clinical experience concerning the evaluation of these patients by means of technetium-99m (99mTc)-somatostatin analog scintigraphy. Furthermore, these radiopharmaceuticals are promising imaging agents owing to their lower cost, availability, dosimetry, and ease of preparation. An 8-year-old boy already diagnosed with stage-IV neuroblastoma received chemotherapy. In the follow-up, after obtaining the parents’ informed consent, iodin 131 (131I)-MIBG and 99mTc-6-hydrazinopyridine-3-carboxylic acid (HYNIC)-octreotide scans were done on separate days to evaluate tumor extension. Even as the 131I-IBG scan showed mild diffuse uptake in the projection of both lung hili, the 99mTc-HYNIC-octreotide scan showed multiple axial and appendicular bone uptakes and paravertebral, abdominal, mediastinal, and supraclavicular ganglionar uptakes. The 99mTc-HYNIC-octreotide showed much more lesion extension than the 131I-MIBG. Therefore, 99mTc-HYNIC-octreotide may be a promising radiopharmaceutical for the evaluation of neuroblastoma patients. This finding justifies the pre liminary evaluation of this tracer in the context of a clinical trial.

Labeling and Biological Evaluation of 99m Tc-HYNIC-Trastuzumab as a Potential Radiopharmaceutical for In Vivo Evaluation of HER2 Expression in Breast Cancer

The amplification of HER2 gene has been described in several tumor types, mainly breast cancer with a subsequent increase in HER2 protein expression. Trastuzumab is a humanized monoclonal antibody that recognizes selectively the HER2 extracellular domain. The objective of the present work was to standardize the conjugation of Trastuzumab with Succinimidyl-hydrazinonicotinamide (HYNIC) and labeling with 99mTc to obtain 99mTc-HYNIC-Trastuzumab for use as in vivo tracer of the HER2 expression in breast cancer. The labeling procedure involved derivatization of 0.067 μmol of Trastuzumab with 0.33 μmols of HYNIC in dimethyl sulfoxide (DMSO). The mixture was incubated for 30 min. A mixture of Tricine and SnCl2.2H2O was prepared by add a solution of 44.6 μmols Tricine in 0.05 mL HCl 2.0 M and a similar volume of another solution containing 44.3 μmols SnCl2.2H2O in 0.5 mL HCl 2.0 M. Then, 0.05 mL of this mixed was added to the conjugated with 296 MBq of 99mTcO-4. The final mixture was incubated at room temperature (18-25°C) for 30 min. Radiochemical purity of the labeled solution was studied by chromatography, to evaluate 99mTc-Tricine, 99mTcO2.H2O, and free 99mTcO4−. Radiochemical purity was also evaluated by HPLC. Stability studies were tested in solution at 4°C and lyophilized at 4°C. Biodistribution studies were performed in healthy CD-1 female mice at 2, 5, and 24 h (n = 3) and CD-1 female mice spontaneous breast adenocarcinoma (n = 3). Scintigraphic images of spontaneous breast adenocarcinoma in female CD-1 mice were acquired in a gamma camera at 2, 5, and 24 h post-injection. Labeling was easily performed with high yields (>90%) and radiopharmaceutical stability for 24 h post-labeling. Stability studies revealed that antibody derivative must be lyophilized for undamaged storage. Biodistribution studies and imaging revealed excellent uptake in the tumor. Based on the results it was concluded that 99mTc-HYNIC-Trastuzumab could be a promising radiopharmaceutical for in vivo diagnosis of the HER2 status in breast with impact on treatment planning.

In vivo visualization of somatostatin receptor expression with Ga-68-DOTA-TATE PET/CT in advanced metastatic prostate cancer.

Abstract:Recently, combination therapies with somatostatin analogs have emerged as a therapeutic option for patients with androgen-independent advanced prostate cancer. Therefore, the confirmation of a sufficient number of somatostatin receptors to plan a receptor-targeted chemo- or radiation therap

Preparation and Primary Bioevaluation of 99mTc-labeled-1-thio-β-D-Glucose as Melanoma Targeting Agent

The development of specific radiolabeled probes towards molecular markers in vivo has gained interest as targeted imaging agents for a more accurate detection of diseases. The aim of this study was to evaluate early detection of melanoma tumor based on 1-thio-β-D-glucose (1-TG) radiolabeled with technetium-99m. 99mTc-1-TG has been synthesized and evaluated in vitro and in vivo for melanoma uptake. Tumor-cell uptake of the 99mTc complex was performed with cultured B16F1 murine melanoma cells which were also used for the in vivo studies. The methodology consisted in radiopharmaceutical synthesis followed by intravenous administration of 99mTc-1-TG in melanoma bearing mice and scintigraphic imaging. 1-thio-β-D-glucose was labeled with 99mTc under reductive conditions using SnCl2. Radiolabeling efficiency was > 96%. 99mTc-1-TG showed high melanoma uptake in vitro. This was confirmed in vivo since a significant difference of 99mTc-1- TG uptake between melanoma model and the control joint was observed. General biodistribution showed renal uptake. The scintigraphic images showed tumor selective uptake of the 1-TG labeled, in tumor-bearing mice This study indicates effective labeling of 1-thio-β-D-glucose with 99mTc that shows potential as a new type of specific probe for melanoma detection.

Evaluation of Patients with Head and Neck Cancer by Means of 99mTc-Glucarate

Preliminary findings have suggested that 99mTc-glucarate has tumor-seeking properties. The purpose of this study was to explore the potential of this tracer to evaluate malignant head and neck tumors by means of SPECT/CT software fusion imaging. Methods: Eleven male patients with advanced head and neck carcinoma were included in the study: 9 with locally advanced disease and 2 with clinical suspicion of local relapse. Scanning started 3–6 h after the injection of 1,110 MBq of 99mTc-glucarate. Planar and SPECT images of the head, neck, and thorax were acquired. Three-dimensional images were also coregistered with CT. Results: We found 99mTc-glucarate uptake in all suspected lesions. SPECT/CT fusion imaging was helpful in all cases for topographically localizing the tracer foci. Conclusion: 99mTc-glucarate can be considered a potential tracer for the evaluation of patients with head and neck tumors.

Early Detection of Bone Metastasis in Small Cell Neuroendocrine Carcinoma of the Cervix by 68Ga-DOTATATE PET/CT Imaging

The neuroendocrine small cell carcinoma of the cervix is a rare malignancy that has a poor prognosis due to early lymphatic and hematogenous spread. We herein report a case of a 27- year-old woman who was referred for initial staging of a neuroendocrine small cell carcinoma with previous unremarkable structural imaging. Ga-DOTATATE PET/CT revealed focal uptake at the primary tumor and in a solitary pelvic bone lesion suggestive of metastases that was further confirmed by CT-guided biopsy. Somatostatin receptor PET/CT may be a useful image modality for early detection of metastases to guide treatment in these patients.

18 F-FDG PET-CT for Staging of Conjunctival Melanoma

The value of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET-CT) for the evaluation of cutaneous melanoma has been demonstrated previously. However, there are few reports regarding the use PET-CT for the staging of conjunctival melanoma (CM). We report here a case, a 34-year-old male with a six-month history of a pigmented nodule at the palpebral conjunctiva of the left eye, and a firm left preauricular lymph node detected on physical examination. Biopsy of the ocular lesion confirmed CM, and fine needle aspiration cytology of the preauricular node was positive for malignancy. CT showed three pulmonary nodules. An 18F-FDG PET-CT was performed to restage the patient. The study showed hypermetabolic lesions in the left eye, and in the left preauricular node. The scan was negative for metastasis. These findings were important in guiding management of the disease in this patient. Future prospective studies should further evaluate the role of 18F-FDG PET-CT for the staging of CM.