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PURPOSE: Ac-225 labeled with prostate-specific membrane antigen (PSMA-617), a transmembrane glycoprotein which is highly expressed in prostate carcinoma cells, is presently being considered a promising agent of targeted alpha therapy for the treatment of patients suffering from metastatic castration-resistant prostate cancer. In the present study, we report an optimized protocol for the preparation of therapeutic dose of Ac-225 PSMA-617 with high yield and radiochemical purity (RCP). METHODS: Ac-225 PSMA-617 was prepared by adding the peptidic precursor-PSMA-617 (molar ratios, Ac-225: PSMA-617 = 30:1) in 1 ml ascorbate buffer to Ac-225 and heating the reaction mixture at 90°C for 25 min to obtain the radiopeptide with high RCP and yield. The radiolabeled peptide was administered in patients who met the eligibility criteria and posttherapy assessment was done. RESULTS: Ten batches of Ac-225 PSMA-617 were prepared following this protocol. The radiopeptide was obtained with an adequate yield of 85%-87% and RCP of 97%-99%. CONCLUSION: The current protocol allows single-step, successful, routine inhouse radiolabeling of Ac-225 with PSMA-617 with high yield and RCP.
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18F-2-fluoro-2-deoxy-D-glucose ([18F]-FDG) positron emission tomography (PET) CT has proven useful in the evaluation of high-grade glioma and is also useful as a predictor of the degree of malignancy in newly diagnosed brain tumors. It is commonly accepted that high-grade gliomas are characterized by increased FDG uptake, whereas the low-grade glioma demonstrates reduced or absent FDG uptake. [18F]-FDOPA is an amino acid PET tracer which is a marker of the proliferative activity of brain tumors and demonstrates positive uptake in all grades of brain tumors; however, the degree of tracer uptake is significantly higher in high-grade tumors as compared to low-grade tumors. Here, we discuss a case where both FDG and DOPA PET/CT scans raised suspicion of low-grade glioma; however, the final histopathology report confirmed WHO grade IV Glioblastoma.
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Tumor-induced osteomalacia (TIO) is a curable condition when the tumor is correctly located and completely removed. These tumors are, however, small and located in regions that make surgical removal difficult and sometimes risky in some patients. Experience of radiofrequency ablation (RFA) in the management of TIO is limited. We describe 3 patients with TIO who were treated in our hospital with RFA. They had suspected lesions in surgically difficult locations and were subjected to single sessions of RFA. The response was documented in terms of improvement in symptoms, normalization of hypophosphatemia and hyperphosphaturia, and disappearance of uptake on follow-up Ga68 DOTANOC PET/CT imaging. All 3 patients had a clinical and biochemical profile consistent with TIO. The first patient (patient 1) had an intensely Ga68 DOTANOC avid lesion involving the roof of right acetabulum. The second patient (patient 2) had a Ga68 DOTANOC avid intramuscular lesion in left pectineus muscle and the third patient (patient 3) had a Ga68 DOTANOC avid expansile osteolytic lesion involving the angle and ramus of right mandible. All 3 patients achieved complete biochemical as well as clinical remission with single sessions of RFA. Six months after the procedure, Ga68 DOTANOC imaging revealed the absence of uptake at the previous sites, corroborating with the clinical improvement and normalization of hypophosphatemia and hyperphosphaturia. In conclusion, although surgical resection is the standard of care, RFA can be used successfully for treating patients with TIO. It can be an effective, less invasive, and safe modality of treatment in those patients where resection of the lesion is not possible because of inaccessible anatomical location or comorbidity that prohibits surgery. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
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PURPOSE: This is a prospective non-randomized observation study done on 33 patients with uncomplicated spinal tuberculosis to observe the imaging characteristics on sequential F-18 FDG PET CT scans. METHODS: 33 consecutive patients with pathologically proven spinal tuberculosis underwent a baseline contrast-enhanced whole body FDG PET scan before initiation of antitubercular therapy, 6 and 12 months and at 18 months or the end of antitubercular therapy. RESULT: The baseline peak SUVmax of lesions in our 33 cases had values ranging from 5.9 to 30.3 (mean 14.8). 63.6 % patients had clinically occult non-contiguous multifocal skeletal involvement at the time of the baseline whole body PET CT scanning. The mean change in SUVmax at various time points was highly significant (p value < 0.001). CONCLUSION: SUVmax can be taken as a reliable marker for serial quantification of metabolic activity in spinal tuberculosis. This may translate into a potential role for FDG as an imaging biomarker for noninvasive response evaluation in skeletal tuberculosis.
