Assessment of endometriosis angiogenesis using 99mTc-maraciclatide imaging (DETECT): a single-centre, exploratory, open-label, non-randomised, phase 2 study

Background Novel non-invasive or minimally invasive diagnostic tests for endometriosis are a research priority. Superficial peritoneal endometriosis, the most prevalent subtype of endometriosis (80% of all laparoscopically diagnosed disease), currently eludes reliable detection by standard imaging techniques (eg, transvaginal ultrasound and MRI). We aimed to evaluate the diagnostic potential and accuracy of 99mTc-maraciclatide, a gamma-emitting radiotracer that binds to αvβ3 integrins for imaging inflammatory diseases, in people with endometriosis. Methods The DETECT study was a prospective, single-centre, exploratory, open-label, non-randomised, phase 2 study in a tertiary hospital setting that generated single-photon-emission CT-CT (SPECT-CT) imaging data before surgery (the reference standard). The Women's Centre and Oxford Endometriosis CaRe Centre (University of Oxford, Oxford, UK) served as the recruiting site, with scans performed at the Royal United Hospital (Bath, UK). Female participants aged 18 years and older with confirmed or suspected endometriosis based on previous clinical investigation and who were due to have a diagnostic or therapeutic laparoscopy or thoracoscopic surgery were recruited to the study. Participants underwent preoperative imaging with 10-min or 20-min SPECT-CT, with intravenous 99mTc-maraciclatide administered as a bolus followed by saline flush. The primary outcome was agreement of radiological and surgical findings in participants completing both imaging and surgery and was assessed per protocol. The surgical report and World Endometriosis Research Foundation surgical form on lesion type and location were compared with images for alignment. Safety was assessed in all participants who underwent the SPECT-CT scan from the time of administering 99mTc-maraciclatide and for the duration of the imaging day. The study is registered with ClinicalTrials.Gov, NCT05623332, and is active. Findings Between March 6, 2023, and Sept 16, 2024, 20 participants were recruited and imaged. Of the 20 participants recruited, 17 (85%) underwent laparoscopy and two (10%) had thoracoscopy after SPECT-CT imaging. Imaging results were concordant with the surgical presence or absence of endometriosis in 16 (84%, 95% CI 60–97) of the 19 participants who completed the study, with endometriosis imaged in 14 (82%) of 17 surgically positive participants, including two participants with thoracic endometriosis. Although the study was not powered for definitive diagnostic accuracy, participant-level sensitivity was calculated to be 82% (95% CI 57–96) and specificity to be 100% (16–100). There were no serious adverse events during the study or adverse events that resulted in participant withdrawal from the study. Interpretation The DETECT study highlights the potential of imaging with 99mTc-maraciclatide to identify endometriosis, especially superficial peritoneal endometriosis. If the effectiveness of this technique is supported in a larger study, there might be a role for 99mTc-maraciclatide as a novel diagnostic tool for endometriosis. Funding National Institute for Health and Care Research Oxford Biomedical Research Centre and Serac Healthcare