Abstract
The theranostic concept represents a paradigmatic example of personalized treatment. It is based on the use of radiolabeled compounds which can be applied for both diagnostic molecular imaging and subsequent treatment, using different radionuclides for labelling. Clinically relevant examples include somatostatin receptor (SSTR)-targeted imaging and therapy for the treatment of neuroendocrine tumors (NET), as well as prostate-specific membrane antigen (PSMA)-targeted imaging and therapy for the treatment of prostate cancer (PC). As such, both classes of radiotracers can be used to triage patients for theranostic endoradiotherapy using positron emission tomography (PET). While interpreting PSMA- or SSTR-targeted PET/computed tomography scans, the reader has to navigate certain pitfalls, including (I.) varying normal biodistribution between different PSMA- and SSTR-targeting PET radiotracers, (II.) varying radiotracer uptake in numerous kinds of both benign and malignant lesions, and (III.) resulting false-positive and false-negative findings. Thus, two novel reporting and data system (RADS) classifications for PSMA- and SSTR-targeted PET imaging (PSMA- and SSTR-RADS) have been recently introduced under the umbrella term molecular imaging reporting and data systems (MI-RADS). Notably, PSMA- and SSTR-RADS are structured in a reciprocal fashion, i.e., if the reader is familiar with one system, the other system can readily be applied. Learning objectives of the present case-based review are as follows: (I.) the theranostic concept for the treatment of NET and PC will be briefly introduced, (II.) the most common pitfalls on PSMA- and SSTR-targeted PET/CT will be identified, (III.) the novel framework system for theranostic radiotracers (MI-RADS) will be explained, applied to complex clinical cases and recent studies in the field will be highlighted. Finally, current treatment strategies based on MI-RADS will be proposed, which will demonstrate how such a generalizable framework system truly paves the way for clinically meaningful molecular imaging-guided treatment of either PC or NET. Thus, beyond an introduction of MI-RADS, the present review aims to provide an update of recently published studies which have further validated the concept of structured reporting systems in the field of theranostics.
Highlights
Theranostics is a paradigm-setting example of personalized medicine
Med. 2019, 8, 1060 generalizable framework systems for standardized reporting in the field [17]. Such framework systems would I) help convey to the nuclear medicine scan reader the level of certainty that an equivocal finding is a site of disease; II) help to navigate common pitfalls of either prostate-specific membrane antigen (PSMA)- or somatostatin receptor (SSTR)-positron emission tomography (PET)/CT; III) facilitate communication with referring clinicians; IV) allow for comparison of results derived from multicenter studies; and V) identify appropriate candidates for treatment with 177Lu-labeled compounds in a tJh. eCrliann
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Summary
Theranostics is a paradigm-setting example of personalized medicine. It is based on the use of radiolabeled compounds which can be applied for both diagnostic molecular imaging and subsequent treatment, using different radionuclides for labelling. The rising frequency of SSTR-PET to assess putative sites of disease in gastroenteropancreatic (GEP) NET patients has generated evidence of various benign and malignant conditions which may have discernible radiotracer uptake Such conditions include: I) localized inflammation (e.g., prostatitis, post-radiation induced inflammation, large artery inflammation, atherosclerosis, culprit carotid lesions, (cardiac) sarcoidosis, myocardial infarction) [22,28,29,30,31,32,33,34]; II) lesions of osteoblastic nature (e.g., degenerative structures, fracture, vertebral hemangioma) [20,22]; III) other rare non-GEP NET tumors (medullary thyroid carcinoma) [35]; or IV) incidental non-NET tumors Such discrepant findings with different radiopharmaceuticals highlight the importance of structured reporting systems for patients with different tumor load, as lesions with moderate to faint uptake may be missed, especially close to a normal organ with exaggerated uptake
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