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Purpose: Classical brachytherapy of solid malignant tumors is an invasive procedure which often results in an uneven dose distribution, while requiring surgical removal of sealed radioactive seed sources after a certain period of time. To circumvent these issues, we report the synthesis of intrinsically radiolabeled and gum Arabic glycoprotein functionalized [169Yb]Yb2O3 nanoseeds as a novel nanoscale brachytherapy agent, which could directly be administered via intratumoral injection for tumor therapy. Methods: 169Yb (T½ = 32 days) was produced by neutron irradiation of enriched (15.2% in 168Yb) Yb2O3 target in a nuclear reactor, radiochemically converted to [169Yb]YbCl3 and used for nanoparticle (NP) synthesis. Intrinsically radiolabeled NP were synthesized by controlled hydrolysis of Yb3+ ions in gum Arabic glycoprotein medium. In vivo SPECT/CT imaging, autoradiography, and biodistribution studies were performed after intratumoral injection of radiolabeled NP in B16F10 tumor bearing C57BL/6 mice. Systematic tumor regression studies and histopathological analyses were performed to demonstrate therapeutic efficacy in the same mice model. Results: The nanoformulation was a clear solution having high colloidal and radiochemical stability. Uniform distribution and retention of the radiolabeled nanoformulation in the tumor mass were observed via SPECT/CT imaging and autoradiography studies. In a tumor regression study, tumor growth was significantly arrested with different doses of radiolabeled NP compared to the control and the best treatment effect was observed with ~ 27.8 MBq dose. In histopathological analysis, loss of mitotic cells was apparent in tumor tissue of treated groups, whereas no significant damage in kidney, lungs, and liver tissue morphology was observed. Conclusions: These results hold promise for nanoscale brachytherapy to become a clinically practical treatment modality for unresectable solid cancers. [ABSTRACT FROM AUTHOR]

Fibroblast activation protein (FAP) is a type II membrane-bound glycoprotein which is overexpressed in cancer-associated fibroblasts and activated fibroblasts at wound healing/inflammatory sites. Since the first clinical application of quinoline-based FAP ligands in 2018, FAP inhibitor (FAPI)-based PET imaging and radiotherapy have been investigated for a wide variety of diseases, both cancerous and non-cancerous. As a consequence, promising strides have been made in particular to improve the understanding of FAPI-based PET imaging and the potential value of FAPI-based tumor radiotherapy. Herein, we present a comprehensive review of radiolabeled FAPI, including their clinical translation, in order to clarify the current and potential future role of this class of molecules in nuclear medicine. In particular, this review underlines the value of FAPI radiopharmaceuticals in the diagnosis or therapy of tumors or benign conditions. However, limitations in present studies have hampered a precise evaluation of FAPI radiopharmaceuticals. Despite this, it will likely be worthwhile to further explore the clinical value of FAPI in diagnosis and therapy through better-designed and larger-population clinical trials in the future. [ABSTRACT FROM AUTHOR]

Purpose: Without a standard test for pancreatic carcinomas, this highly lethal disease is normally diagnosed at its advanced stage, leading to a low survival rate of patients. Trophoblast cell-surface antigen 2 (Trop-2), a transmembrane glycoprotein, is associated with cell proliferation and highly expressed in most of solid epithelial tumors, including pancreatic cancer. A non-invasive method of imaging Trop-2 would greatly benefit clinical diagnosis and monitoring of pancreatic cancer. In the current study, 89Zr-labeled anti-Trop-2 antibody (AF650) was recruited for the systemic evaluation of Trop-2 as an immunoPET target for pancreatic cancer imaging. Methods: AF650 was conjugated with desferrioxamine (DFO) and then radiolabeled with 89Zr. Trop-2 expression levels were determined in three pancreatic cancer cell lines (BxPC-3, MIA PaCa-2, and AsPC-1) via western blot, flow cytometry, saturation binding assay, and immunofluorescence staining. The targeting capacity of 89Zr-DFO-AF650 was evaluated in mouse models with subcutaneous xenograft of pancreatic cancers via PET imaging and bio-distribution studies. In addition, a Trop-2-positive orthotopic cancer model was recruited for further validating the targeting specificity of 89Zr-DFO-AF650. Results: BxPC-3 cells expressed high levels of Trop-2, while AsPC-1 and MIA PaCa-2 cells expressed low levels of Trop-2. Additionally, 89Zr-DFO-AF650 exhibited high specificity to Trop-2 in BxPC-3 cells (Kd = 22.34 ± 2.509 nM). In subcutaneous xenograft models, about 28.8 ± 7.63%ID/g tracer accumulated in the BxPC-3 tumors at 120 h post injection, which was much higher than those reaching MIA PaCa-2 (6.76 ± 2.08%ID/g) and AsPC-1 (3.51 ± 0.69%ID/g) tumors (n = 4). More importantly, 89Zr-DFO-AF650 could efficiently distinguish primary tumors in the orthotopic BxPC-3 cancer model, showing high correlation between PET imaging and bio-distribution and sensitivity. Conclusions: 89Zr-DFO-AF650 can be effectively used to detect pancreatic cancer via Trop-2-mediated immunoPET in vivo, clearly revealing the great potential of Trop-2-based non-invasive imaging in pancreatic cancer detection and treatment monitoring. [ABSTRACT FROM AUTHOR]

With continued development and optimization of the PET/CT scanner, as well as cost reduction, we believe LAFOV PET/CT scanners will become widely available in the future, just like PET/CT scanners have replaced PET scanners more than a decade ago [[41]]. Although the CT dose was not specifically stated, the effective radiation dose associated with this type of low-dose CT scan is approximately 2-3 mSv, which is significantly lower than a typical diagnostic body CT exam and the CT component of a typical modern PET/CT exam (~ 5-10 mSv) [[21]-[23]]. With the constant advancements of CT tube and detector technologies [[24]], as well as artificial intelligence (AI)-based CT dose reduction technologies (e.g., TrueFidelity Deep Learning Image Reconstruction from GE Healthcare [[25]] and Advanced Intelligent Clear-IQ Engine from Canon Medical Systems USA Inc. [[27]-[29]]), it is very likely that the CT component of LAFOV PET/CT exam will be further reduced to the sub-mSv level in the near future, which means the entire whole-body PET/CT exam with a low dose of injected PET tracer can be achieved below 2 mSv. 10.1007/s00259-021-05357-5. 33866409 20 Tan H, Sui X, Yin H, Yu H, Gu Y, Chen S. Total-body PET/CT using half-dose FDG and compared with conventional PET/CT using full-dose FDG in lung cancer. [Extracted from the article]

A correction is presented to the article "Clinical summary of fibroblast activation protein inhibitor‑based radiopharmaceuticals: cancer and beyond.