Myocardial flow reserve (MFR) measured by 13N-ammonia PET is a well-established indicator of adverse outcomes in patients with ischemic heart disease (IHD), with a low MFR (<2.0) indicating a poor prognosis. Furthermore, MFR can be used to non-invasively diagnose ischemia with non-obstructive coronary arteries. However, most of the evidence originates from Western populations, and studies in Japan are limited to small sample sizes. Therefore, we aimed to investigate the utility of MFR for risk stratification of cardiovascular events in a Japanese cohort.Between January 2016 to December 2023, consecutive 413 Japanese patients who underwent NH3-PET because of known or suspected IHD at multiple facilities in Japan were analyzed. We evaluated myocardial blood flow (MBF) at rest and during adenosine-induced hyperemic stress, and calculated MFR from the ratio of stress to rest MBF. The patients were divided into two groups according to MFR as defined by receiver-operating characteristic (ROC) analysis. The frequency of major adverse cardiovascular events (MACE), including acute coronary syndrome, revascularization after three months, heart failure hospitalization, and all-cause mortality, was compared by Kaplan-Meier and log-rank test. For imaging and clinical parameters, hazard ratios (HR) and 95% confidence intervals (CI) were calculated using the Cox proportional hazards regression model.The ROC curve analysis of MFR for MACE showed the optimal cutoff value of 2.1. The incidence of MACE in the group with reduced MFR was significantly higher than that with preserved MFR (p < 0.0001). MFR and summed stress score were significant factors in univariate analysis. Multivariate analysis indicated that MFR was an independent prognostic factor of MACE (HR: 0.50, 95% CI: 0.36-0.70, p < 0.0001).In Japan, MFR derived from NH3-PET was also a useful prognostic factor. The cutoff value for MFR was comparable to that reported in previous studies involving patients in the West.

This survey was performed in order to investigate the incidence of adverse reactions to radiopharmaceuticals in FY2024 in Japan. It was based on responses to questionnaires sent to nuclear medicine institutions. Replies were obtained from 989 institutions out of 1,176 to which the questionnaire had been sent. A total of 925,315 radiopharmaceutical administrations were reported. Nine cases of adverse reactions were reported. The incidence of adverse reactions per 100,000 cases was 1.0. No case of defective products was reported.

Radionuclide therapy often involve long waiting periods due to limited numbers of radioisotope therapy rooms and special measures rooms, and strict regulations. The purpose of this study was to estimate the waiting period for radionuclide therapy, considering the increased utilization of nuclear medicine and greater demand due to new drugs. The study also examined possible factors that may limit the treatment provision system and investigate appropriate treatment environments that could shorten the waiting period. We developed a discrete event simulation, using three prefectures as a model, to predict the number of patients with a long waiting period and determine the effectiveness of environmental measures designed to shorten the waiting period. The model took considered the demand for radionuclide therapy and medical resources, such as the number of treatment beds, as input values. The simulation predicted that, within 4 years after the introduction of [177Lu]Lu-PSMA-617, the number of patients waiting >180 days for treatment would increase significantly in all three prefectures. The limited number of beds was the leading cause of the long waiting period. However, just increasing the number of beds was ineffective for reducing the waiting period in some facilities due to regulatory factors, and measures to improve the drainage capacity were also necessary. The number of patients with a long waiting period is expected to increase significantly due to the rapid increase in demand for radionuclide therapy. A combination of measures, including increasing the number of beds, improving drainage capacity, and better utilization of available medical resources through interfacility cooperation, are factors that need urgent attention to reduce the waiting time for radionuclide therapy.

The Japanese government has shown increasing expectations for the medical application of radioactive isotopes (RIs), as reflected in the 2024 Basic Policy on Economic and Fiscal Management and Reform. Additionally, the Fukushima Instutute for Research, Education and Innovation (F-REI) has launched RI-based diagnostic and therapeutic drug development projects, and the Ministry of Health, Labour and Welfare has proposed a draft guideline for clinical and non-clinical studies of radiopharmaceuticals for therapeutic use. Meanwhile, in Europe, three large-scale theranostics projects began in October 2024. These projects represent the first public-private research initiatives in RI drug discovery, with significant financial support of 60 million euros from the Horizon Europe project of the European Commission and the related industries. In terms of drug development, the Innovative Health Initiative (IHI) plays a key role in funding medical research projects as part of Horizon Europe. It designated the Thera4Care, Accelerate.EU, and ILLUMINATE projects, focusing on theranostics. Thera4Care aims to establish ecosystem for theranostics and expand its use across Europe. Accelerate.EU aims to develop targeted alpha therapy using astatine-211 (211At) for pancreatic, breast, and brain cancers, establishing a sustainable production network. The project plans to conduct phase1 clinical trials by 2028. ILLUMINATE focuses on optimizing lutetium-177 (177Lu)-based therapies for prostate cancer while improving isotope production and supply chains. Japan has RI research initiatives sponsored by F-REI, but lacks strong industry participation and financial contribution mechanisms seen in Europe. It is desirable for researchers to inform companies and related organizations about commissioned projects, and for researchers themselves to improve the environment for joint research. The advancement of theranostics using RIs in Japan requires industry engagement, knowledge dissemination, and workforce training to facilitate clinical applications and foster international collaboration.