ABSTRACT
The field of nuclear theranostic clinical trials is continuously expanding as an increasing number of novel agents and treatment combinations are explored for treating advanced and metastatic cancers. Moving from 'bench-to-bedside' is oftentimes a complex and lengthy process. The objective of this overview is to explore the basic elements involved in designing clinical trials with a special focus on theranostics in nuclear medicine. The 'bench-to-bedside' journey involves translating basic scientific research into patient-effective treatments. Preclinical studies, a crucial initial step, are a complex process encompassing in vitro experiments, in vivo studies, and animal models to explore hypotheses in humans. Clinical trials follow, with predefined phases assessing safety, effectiveness, and comparisons to existing treatments. This process demands investments in data management, statistics, good clinical practice (GCP) accreditations, and collaborative efforts for funding and sustainable pricing. Theranostics, merging diagnostics and personalized treatment, is at the forefront. Continuous efforts to enhance existing agents involve reducing adverse effects, exploring new indications, and incorporating advanced imaging modalities. Radionuclide therapy, unique with non-uniform distribution and complex radiobiology, plays a distinct role. This article explores trends and challenges in each clinical trial phase in light of the emerging field of theranostics in nuclear medicine, emphasizing meticulous trial design, dosimetry optimization, and the necessity of collaborative stakeholder efforts for successful implementation.
ABSTRACT
BACKGROUND: New digital detectors and block-sequential regularized expectation maximization (BSREM) reconstruction algorithm improve positron emission tomography (PET)/magnetic resonance (MR) image quality. The impact on image quality may differ from analogue PET/computed tomography (CT) protocol. The aim of this study is to determine the potential reduction of injected [68Ga]Ga-DOTA-TATE activity for digital PET/MR with BSREM reconstruction while maintaining at least equal image quality compared to the current analogue PET/CT protocol. METHODS: NEMA IQ phantom data and 25 patients scheduled for a diagnostic PET/MR were included. According to our current protocol, 1.5 MBq [68Ga]Ga-DOTA-TATE per kilogram (kg) was injected. After 60 min, scans were acquired with 3 (≤ 70 kg) or 4 (> 70 kg) minutes per bedposition. PET/MR scans were reconstructed using BSREM and factors ß 150, 300, 450 and 600. List mode data with reduced counts were reconstructed to simulate scans with 17%, 33%, 50% and 67% activity reduction. Image quality was measured quantitatively for PET/CT and PET/MR phantom and patient data. Experienced nuclear medicine physicians performed visual image quality scoring and lesion counting in the PET/MR patient data. RESULTS: Phantom analysis resulted in a possible injected activity reduction of 50% with factor ß = 600. Quantitative analysis of patient images revealed a possible injected activity reduction of 67% with factor ß = 600. Both with equal or improved image quality as compared to PET/CT. However, based on visual scoring a maximum activity reduction of 33% with factor ß = 450 was acceptable, which was further limited by lesion detectability analysis to an injected activity reduction of 17% with factor ß = 450. CONCLUSION: A digital [68Ga]Ga-DOTA-TATE PET/MR together with BSREM using factor ß = 450 result in 17% injected activity reduction with quantitative values at least similar to analogue PET/CT, without compromising on PET/MR visual image quality and lesion detectability.
ABSTRACT
PURPOSE: The purpose of this study was to investigate whether 18F-fluorodeoxyglucose ( 18 F-FDG) PET/MRI may potentially improve tumor detection after neoadjuvant chemoradiotherapy (nCRT) for esophageal cancer. METHODS: This was a prospective, single-center feasibility study. At 6-12 weeks after nCRT, patients underwent standard 18 F-FDG PET/computed tomography (CT) followed by PET/MRI, and completed a questionnaire to evaluate burden. Two teams of readers either assessed the 18 F-FDG PET/CT or the 18 F-FDG PET/MRI first; the other scan was assessed 1 month later. Maximum standardized uptake value corrected for lean body mass (SUL max ) and mean apparent diffusion coefficient (ADC mean ) were measured at the primary tumor location. Histopathology of the surgical resection specimen served as the reference standard for diagnostic accuracy calculations. When patients had a clinically complete response and continued active surveillance, response evaluations until 9 months after nCRT served as a proxy for ypT and ypN (i.e. 'ycT' and 'ycN'). RESULTS: In the 21 included patients [median age 70 (IQR 62-75), 16 males], disease recurrence was found in the primary tumor in 14 (67%) patients (of whom one ypM+, detected on both scans) and in locoregional lymph nodes in six patients (29%). Accuracy (team 1/team 2) to detect yp/ycT+ with 18 F-FDG PET/MRI vs. 18 F-FDG PET/CT was 38/57% vs. 76/61%. For ypN+, accuracy was 63/53% vs. 63/42%, resp. Neither SUL max (both scans) nor ADC mean were discriminatory for yp/ycT+â . Fourteen of 21 (67%) patients were willing to undergo a similar 18 F-FDG PET/MRI examination in the future. CONCLUSION: 18 F-FDG PET/MRI currently performs comparably to 18 F-FDG PET/CT. Improvements in the scanning protocol, increasing reader experience and performing serial scans might contribute to enhancing the accuracy of tumor detection after nCRT using 18 F-FDG PET/MRI. TRIAL REGISTRATION: Netherlands Trial Register NL9352.
