To update the rurality index for Japan (RIJ) using the most recent national data and to test and evaluate the updated RIJ variants that incorporate alternative distance metrics and a modified classification of remote islands, thereby providing methodological guidance for their use in research and health policy.

Nationwide methodological study.

Japan.

All postal code areas in Japan; analyses were aggregated into municipalities and secondary medical care areas for evaluation.

Six RIJ variants (‘RIJ family’) constructed by combining three distance metrics (direct distance, road-based distance and travel time by car) and two island classifications (original RIJ and modified RIJ), standardised to a continuous 0–100 scale using percentile ranks.

Concordance among RIJ variants was assessed using Spearman’s rank correlation coefficients, quintile reclassification matrices and rank-difference analyses; convergent validity was evaluated using the national physician distribution index. Criterion-related validity was assessed using municipal-level life expectancy for men and women.

All RIJ variants had extremely high concordance (Spearman’s ≥0.99 across all pairwise comparisons). Compared with the previous RIJ classification, >98% of the geographic units remained in the same rurality quintile and

Despite differences in distance metrics and island classification, all RIJ variants captured highly similar underlying dimensions of rurality and demonstrated comparable validity. These findings indicate that rurality measurement in Japan is stable regardless of methodological refinements, allowing RIJ variants to be flexibly selected according to specific research or policy purposes without materially affecting conclusions.

Addition of bevacizumab and paclitaxel as induction therapy prior to standard atezolizumab and nab-paclitaxel in patients with programmed death-ligand 1 (PD-L1)-positive metastatic triple-negative breast cancer (mTNBC) may help to overcome vascular endothelial growth factor-associated resistance mechanisms that limit the immune-mediated antitumour efficacy of atezolizumab and nab-paclitaxel.

The Induction Therapy of PTX+BV Followed by Atezolizumab+Nab-PTX for PD-L1+TNBC (INDUCE) study is a multicentre, randomised, open-label, phase II trial designed to evaluate the efficacy and safety of two cycles of induction therapy with bevacizumab and paclitaxel followed by atezolizumab and nab-paclitaxel compared with standard atezolizumab and nab-paclitaxel in patients with PD-L1-positive mTNBC. The primary outcome of the study is progression-free survival (PFS) per Response Evaluation Criteria In Solid Tumours, V.1.1. We have estimated that 89 PFS events are needed to allow a power of 80% to detect a difference between treatment groups at a one-sided significance level of 10% in this study. The target sample size is set to 106 patients to account for dropouts.

The study protocol and informed consent form have been approved by the Certified Research Review Board at the Nagoya University Graduate School of Medicine, Nagoya, Japan. Study results will be presented at international conferences and published in a peer-reviewed journal.

jRCTs041240039 NCT06793553.

Chronic central serous chorioretinopathy (CSC) can cause progressive and permanent vision loss. Although photodynamic therapy (PDT) is a primary treatment option globally, it is not approved for CSC worldwide, limiting therapeutic access. The REPLAY trial is a phase III, investigator-initiated trial to evaluate the efficacy and safety of reduced-fluence PDT (rf-PDT) for chronic CSC to seek the first regulatory approval globally.

This study comprises two cohorts. The ‘untreated cohort’ is a multicentre, randomised, placebo-controlled, double-masked trial involving 60 patients with untreated, fovea-involving chronic CSC, randomised 2:1 to receive a single rf-PDT or placebo treatment. The ‘previously treated cohort’ is a single-arm, open-label trial for up to 10 patients with recurrent CSC after PDT. The primary endpoint for both cohorts is the proportion of eyes with a complete resolution of subfoveal fluid at 12 weeks post-treatment, assessed by optical coherence tomography. Secondary endpoints include changes in best-corrected visual acuity, central choroidal thickness, recurrence rates and incidence of adverse events over a 48 week follow-up.

The study protocol was approved by the Kyoto University Hospital Institutional Review Board, IRB of Chiba University Hospital, Tokyo Women’s Medical University Institutional Review Board and Institutional Review Board of Kansai Medical University Hospital. Written informed consent is obtained from all participants. The results will be disseminated through publication in a peer-reviewed journal and presentations at scientific conferences.

jRCT2051230156 (URL: https://jrct.mhlw.go.jp/latest-detail/jRCT2051230156).

Guided parent-delivered cognitive behavioural therapy (GPD-CBT) is an evidence-based, low-burden treatment programme for childhood anxiety disorders with demonstrated efficacy, cost-effectiveness and accessibility. However, it has been tested primarily in Western countries, and the efficacy and cost-effectiveness have not been evaluated in Japanese families. The current study aims to examine GPD-CBT’s efficacy and cost-effectiveness in Japanese samples and explore potential cultural adaptations of the programme.

This study is designed as a Bayesian single-blind randomised controlled trial with two parallel groups: GPD-CBT (intervention group) and a waitlist control group. The primary outcome is remission of primary anxiety disorders evaluated through diagnostic interviews by independent evaluators. Secondary outcomes include child and parent-reported child anxiety symptoms, depressive symptoms and life interference. Additionally, measures of parental psychological characteristics, programme acceptability and quality of life are collected. We will conduct qualitative interviews with parents who participated in the programme and therapists who delivered the intervention to explore potential cultural adaptations. We aim to recruit 54–170 families, depending on the results of sequential Bayesian analyses. GPD-CBT consists of seven weekly 20 min sessions and a 1-month follow-up session. Assessments will be conducted at baseline, 13 weeks post randomisation (primary endpoint for between-group comparison), with an additional 25 weeks post randomisation. The waitlist control group will receive GPD-CBT after the 13-week assessment.

This study has been approved by the Ethics Review Committees of Chiba University and the University of Tokyo. We will disseminate results through academic conference presentations and peer-reviewed journal publications. If the GPD-CBT intervention proves efficacious, we will promote wider implementation in Japan through the development of training programmes for mental health professionals and key stakeholders.

jRCT1032250421 (https://jrct.mhlw.go.jp/latest-detail/jRCT1032250421) and jRCT1030250422 (https://jrct.mhlw.go.jp/latest-detail/jRCT1030250422) registered on 9 October 2025.

Oxaliplatin, a key drug in the treatment of colorectal cancer (CRC), can cause oxaliplatin-induced peripheral neuropathy (OIPN) in a dose-dependent manner. These symptoms can severely affect daily life, and chronic OIPN often limits treatment continuation because of its correlation with the cumulative dose of oxaliplatin. Currently, effective preventive measures are unavailable. However, surgical glove compression therapy may reduce paclitaxel-induced neuropathy, suggesting its potential in preventing OIPN.

This multicentre, randomised, open-label, phase II/III trial evaluates surgical glove compression therapy to investigate the possible preventive effects of OIPN in patients with CRC receiving adjuvant capecitabine plus oxaliplatin chemotherapy. Patients with stage III CRC undergoing curative surgery will be enrolled and randomised into two groups. The intervention group will wear two layers of tight-fitting surgical gloves from 30 min before to 30 min after oxaliplatin infusion, whereas the control group will receive standard care. The primary endpoint is the incidence of grade ≥2 chemotherapy-induced peripheral neuropathy (CIPN) based on the Common Terminology Criteria for Adverse Events criteria. Secondary endpoints include quality of life assessments (Functional Assessment of Cancer Therapy/Gynecological Oncology Group-Neurotoxicity-12 and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Chemotherapy-Induced Peripheral Neuropathy 20-item), duration and extent of OIPN as assessed using the Debiopharm Neurologic and Sensory Toxicity Criteria, chemotherapy completion rates, and adverse events. To detect a significant reduction in the incidence of CIPN, 170 patients will be enrolled (36% in the control group vs 15% in the intervention group). The planned case enrolment period is from 1 November 2024 to 31 October 2026.

This trial was approved by the Institutional Review Board of Hiroshima University, Japan (approval no. CRB2024-0008), and has been registered with the Japan Registry of Clinical Trials (jRCTs062240066). The results of this study will be submitted for publication in a peer-reviewed journal and shared with the scientific community at international conferences.

jRCTs062240066

Chronic subdural haematoma (CSDH) is a common neurosurgical condition in older adults, with a recurrence rate of approximately 7.1–13% after burr-hole drainage. Although surgical adjuncts such as subdural drains and middle meningeal artery embolisation may reduce recurrence, these are not suitable for all patients. Pharmacological strategies, including tranexamic acid, Goreisan and carbazochrome sodium sulfonate hydrate, have shown potential, but high-level evidence remains lacking. A prior retrospective study suggested that a triple oral regimen combining these agents may reduce recurrence. This randomised controlled trial aims to evaluate its efficacy and safety.

This is a prospective, multicentre, open-label, randomised controlled trial conducted across six hospitals in Ibaraki, Japan. A total of 180 patients undergoing first-time burr-hole surgery for CSDH will be randomised 1:1 to receive either triple therapy (Goreisan 7.5 g/day, carbazochrome sodium sulfonate hydrate 90 mg/day and tranexamic acid 750 mg/day for up to 90 days) or standard postoperative care. The primary outcome is recurrence requiring reoperation within 90 days. Secondary outcomes include time to recurrence and haematoma volume reduction on serial CT imaging. All analyses will follow the intention-to-treat principle, using logistic regression, Cox proportional hazards models and mixed-effects models.

Written, informed consent will be obtained from all participants at each participating hospital by trained staff from that hospital. The trial protocol has been approved by the ethics committee of the University of Tsukuba Hospital (approval no. TCRB23-025) and the Institutional Review Boards of all participating centres. Study findings will be disseminated through presentations at scientific conferences and publications in peer-reviewed journals. A summary of the results will also be provided to participating institutions and made publicly available in accordance with the BMJ Open data sharing policy.

jRCTs031240007.

The intestinal microbiota of people with Parkinson’s disease (PwP) differs significantly from that of healthy individuals. Given that altered microbiota may play a role in the pathogenesis of Parkinson’s disease, faecal microbiota transplantation (FMT) has been proposed as a potential therapeutic approach. However, the efficacy of FMT in improving motor symptoms in PwP has been inconclusive in some pilot randomised controlled trials (RCT). Previous RCTs on PwP employed simple FMT, but our modified approach—pretreatment with antibiotics before FMT (A-FMT)—has been shown to improve the engraftment rate of given species and the beneficial effects of FMT. This study aims to evaluate the efficacy and safety of A-FMT for PwP, particularly in those with motor fluctuations.

This study is a randomised, double-blind, placebo-controlled, parallel-group study with an 8-week observation period following a single A-FMT. Thirty clinically established PwP with prominent motor fluctuation episodes will be randomised 1:1 to FMT or placebo. Participants in both groups will receive antibiotic treatment prior to colonoscopy for FMT or placebo treatment. Primary and secondary endpoints will include subjective and objective evaluations of motor and non-motor symptoms and will be evaluated before and after antibiotic treatment and at 4 and 8 weeks after the procedure. Exploratory endpoints will include blood and faecal sample analyses, advanced brain MRI and pharmacokinetic assessment of levodopa concentrations during a levodopa challenge test.

This study has been approved by the ethical committee of Juntendo University in August 2024 (J24-005) and will be conducted in accordance with the Declaration of Helsinki, the Japan Ministry of Health, Labour and Welfare Clinical Trials Act and related laws and regulations. All patient data will be anonymised to protect privacy and used solely for study purposes. Results will be published in academic journals and presented at conferences.

jRCTs031240344.

The standard treatment for unresectable head and neck cancer typically involves radiotherapy (RT) alone or chemoradiotherapy (chemo-RT). Non-squamous cell carcinomas exhibit relatively low radiosensitivity, limiting the efficacy of conventional photon RT. Carbon-ion (C-ion) RT, characterised by high linear energy transfer (LET) and high relative biological effectiveness (RBE), has shown promising outcomes in treating radioresistant head and neck cancers. However, local recurrences still occur, and further improvements in treatment outcomes are needed. To enhance the local control rate, an increase in dose-averaged LET (LETd) to the tumour was considered.

Following a simulation study, a clinical trial was conducted to optimise LETd using only C-ion therapy, and its safety was confirmed. However, in this clinical trial, LETd could only be increased to approximately 70 keV/μm. To further escalate LETd, multi-ion therapy using ions heavier than carbon was developed. Simulation studies demonstrated that multi-ion therapy incorporating carbon, oxygen and neon ions could increase LETd up to 90 keV/μm, regardless of tumour size, while maintaining high-dose uniformity within the tumour. Based on these results, a clinical study was planned to evaluate the safety of escalating LETd from 70 keV/μm to 90 keV/μm using multi-ion therapy. The primary objective of this study is to evaluate the safety of escalating LETd to the tumour using multi-ion therapy for head and neck cancer, with the secondary goal of identifying the maximum tolerated LETd.

This is a non-randomised, open-label, phase 1 study focused on LETd escalation. A maximum of 18 patients with histologically confirmed inoperable head and neck malignancies will be enrolled. All patients will receive multi-ion therapy using helium, carbon, oxygen or neon ions, either alone or in combination, at an RBE-weighted dose ranging from 57.6 to 70.4 Gy, delivered in 16 fractions (4 fractions per week) over 4 weeks. The specific dose will be determined according to histology. LETd escalation will begin at 70 keV/μm and will increase by 10 keV/μm increments, reaching a maximum of 90 keV/μm. The safety of multi-ion therapy will be assessed based on the frequency and severity of dose-limiting toxicities, monitored up to 90 days after the initial irradiation. Patients will be followed up according to the protocol for 180 days after the initial multi-ion therapy irradiation.

The study protocol has been approved by the National Institutes for Quantum Science and Technology Certified Review Board (#L24-002). The results will be published in a peer-reviewed journal and presented at a scientific conference.

jRCTs032240451.

The effect of prophylactic clipping for colorectal cold snare polypectomy (CSP) on delayed bleeding (DB) in patients with antithrombotic drugs remains unverified. The aim of the PERCOLD study is to demonstrate the non-inferiority of DB rates in cases without prophylactic clips compared with cases with prophylactic clips in patients taking antithrombotic drugs for colorectal CSP through randomised controlled trial (RCT).

This study is a multicentre prospective parallel-group RCT phase 3 trial that is being conducted at 14 institutions in Japan at the time of writing this manuscript. After providing consent, patients will undergo screening and assessment for study enrolment eligibility. Patients taking antithrombotic drugs (aged 20 years or older at the time of consent and who have agreed to participate in this study) will be selected if they have a preoperative suspected adenoma (including sessile serrated lesion) with an endoscopic diameter of

The trial protocol has been approved by the Chiba University Certified Clinical Research Reviewer Board (CRB3180015), which serves as the central ethics committee, and registered with Japan Registry of Clinical Trials. The current protocol V.1.7, dated 4 October 2024. Written informed consent for participation in the study will be obtained from all participating patients. All participating institutions have formally agreed to conduct the study in accordance with this central approval, and local site permissions were obtained as required by each institution. The results of this study will be submitted for publication in international peer-reviewed journals and the key findings will be presented at international scientific conferences.

Japan Registry of Clinical Trials (jRCT1032230086).

Accidental hypothermia (AH) can occur in mild-to-severe cases; however, its management is crucial in severe cases as it can cause ventricular fibrillation and lead to death. Among various rewarming therapies for AH, endovascular catheter rewarming has been the focus of recent studies as a minimally invasive alternative to invasive internal rewarming, such as extracorporeal membrane oxygenation (ECMO). However, no study has demonstrated the efficacy and safety of endovascular catheter rewarming therapy. This study aimed to validate the efficacy and safety of endovascular catheter rewarming for patients with AH.

The intensive care with endovascular catheter rewarming in accidental severe hypothermia (ICE-CRASH II) study is a multicentre, randomised study of patients with AH. This study will include patients with AH (age ≥65 years, core temperature

This study was approved by the Hokkaido University Certified Review Board (approval number: 024-00013). Written informed consent will be obtained from all the participants or their legally acceptable representatives. The results will be disseminated through publications and presentations.

Japan Registry of Clinical Trials (jRCT1012240051).

Traumatic brain injury (TBI) often causes permanent neurological dysfunction. Although no medication has been validated yet to prevent secondary injury of brain tissue, recent animal studies have reported that perampanel, a glutamine receptor antagonist, could improve the neurological functions of animals with TBI by mitigating the abnormal calcium influx and cell death around the site of primary injury. The present study aims to elucidate the efficacy of perampanel administration in improving the neurological function of patients with TBI.

The perampanel for alleviation of secondary injury in TBI trial is a multicentre, phase-II, open-label randomised controlled trial targeting patients with mild-to-moderate TBI. This trial will include adult TBI patients with a Glasgow Coma Scale score of 9–14 from five tertiary centres. Patients with epilepsy as a comorbidity, delayed presentation of symptoms (>24 hours after injury) or Injury Severity Score of ≥25 will be excluded. The study participants will be randomly assigned to either the perampanel group (2 mg/day) or the control group (fosphenytoin administered at a dose of 15–18 mg/kg/day, followed by 5–7.5 mg/kg/day of fosphenytoin). In both groups, the medication will be initiated within 12 hours of the TBI diagnosis and continued for 7 days. The antiepileptic drugs can be increased, changed or added as necessary if early post-traumatic seizures are observed. The primary outcome is favourable neurological outcome, defined as a Glasgow Outcome Scale Extended score of ≥5 at 90 days after the TBI diagnosis, which will then be compared between the groups through an intention-to-treat analysis.

The present study has been approved by the Certified Review Board of Keio at the principal institution (approval number: N20240004). Written informed consent will be obtained from all participants or their legal representatives. The results will be disseminated via publications and presentations.

Japan Registry of Clinical Trials (jRCTs031250067).