Over the past decades, interest in second breast-conserving therapy (BCT) has increased due to, among others, advances in radiotherapy techniques. Preoperative partial breast irradiation (PBI) is an experimental treatment for patients with low-risk primary breast cancer. This approach can downstage the tumour and may possibly reduce toxicity and improve cosmetic outcomes compared with postoperative radiotherapy. This study aims to evaluate the feasibility of single-dose preoperative PBI and second breast-conserving surgery (BCS) for patients with an ipsilateral recurrent breast event (IRBE) after previous BCT.

The REPEAT trial is a multicentre, prospective, single-arm trial investigating ablative single-dose preoperative PBI in patients with an IRBE. Eligible patients are ≥50 years, have a unifocal non-lobular invasive breast cancer ≤2 cm, Bloom-Richardson grade 1 or 2, oestrogen receptor-positive, human epidermal growth factor receptor 2-negative and clinically negative axillary lymph nodes. The study plans to enrol 25 patients. Radiotherapy planning will involve the use of CT and MRI in the treatment position. Single-dose PBI of 20 Gy to the tumour and 15 Gy to the surrounding 2 cm of breast tissue will be delivered using a conventional or MR-guided linear accelerator. Tumour response will be monitored preoperatively using MRI and liquid biopsies to identify biomarkers for evaluating radiosensitivity. BCS will be performed 3 (±one) weeks post PBI. The primary endpoint is the incidence of grade 2 or higher treatment-associated acute toxicity within 90 days. Secondary endpoints include the evaluation of acute (grade 1) and late toxicity, radiologic and pathologic response, mastectomy rate, patient-reported outcomes, cosmetic outcome, local, regional and distant recurrence rates, survival outcome and biomarkers in liquid biopsies and tumour tissue. Patients will be followed up to 5 years after PBI.

Ethical approval from the Medical Research Ethics Committee of the Amsterdam UMC has been obtained (NL85983.018.24). The results will be disseminated via peer-reviewed academic journal and presentation at conferences. In addition, summaries will be shared with the participating patients.

The trial was registered prospectively on October 11^th 2024 at clinicaltrials.gov (NCT06640881).

Post-traumatic stress disorder (PTSD) is a serious disorder that burdens individuals and society. The current standard of first-line treatment for PTSD is spaced trauma-focused treatment (S-TFT), involving weekly sessions. While effective, S-TFT may take relatively long to complete, especially in patients exposed to multiple potentially traumatic events (PTEs). Massed trauma-focused treatment (M-TFT), involving increased session frequency, potentially results in faster symptom reduction and restoration of quality of life, as well as in a reduction of societal costs. However, M-TFT is not recommended as first-line treatment. This paper describes the research protocol of a single-blind, multicentre randomised controlled trial (RCT) aimed at investigating: (1) the clinical and cost-effectiveness of M-TFT versus S-TFT in employed, multiply traumatised patients who seek first-line treatment for PTSD and (2) predictive and moderating factors related to treatment response.

186 participants are recruited from five centres and will be included if they are ≥18 years old, meet criteria for a Diagnostic and Statistical Manual of Mental Disorders Fifth Edition PTSD diagnosis based on ≥two PTEs, seek treatment for the first time and are employed. Patients with specified comorbid disorders and insufficient Dutch language proficiency are excluded. Participants are randomised to 800 min of either M-TFT or S-TFT. M-TFT consists of two once-weekly preparatory sessions, 10 twice-daily sessions of prolonged exposure, eye movement desensitisation and reprocessing therapy for 2 weeks and two once-weekly closing sessions. S-TFT consists of weekly sessions of one of five evidence-based treatment interventions. Outcomes are assessed at baseline and at 7 weeks, 17 weeks, 6 months and 9 months after baseline. Primary outcomes are clinical effectiveness in terms of PTSD symptom severity and cost-effectiveness based on quality of life measures and societal costs. Data will be analysed with linear mixed models.

This study protocol was approved by the Medical Ethics Review Board of the Amsterdam University Medical Center (NL86057.018.24). Participants will provide informed consent before enrolment in the trial. Results will be published in peer-reviewed journals and will be released to clinicians, patient groups and the general community.

This protocol is registered at Overview of Medical Research in the Netherlands (OMON; trial register number 56960) and ClinicalTrials.gov (NCT06700590).