The nine-year wait for an answer
Women in the UK face an average of nine years and four months before receiving an official endometriosis diagnosis — a figure that has risen from eight years in 2020 and eight years and ten months in 2023, according to data from the Nuffield Department of Women’s & Reproductive Health at the University of Oxford. Symptoms such as extremely painful and heavy periods, fatigue, and discomfort during sex or when using the toilet are routinely mistaken for other conditions, most commonly Irritable Bowel Syndrome. The problem is compounded by under-resourced gynaecology services, a tendency among some health professionals to minimise menstrual pain, and the absence of reliable, non-invasive diagnostic tools. For women from ethnic minority communities, the average wait can stretch to 11 years. Now, a new imaging technique promises to change that.
How the new scan works
The technology centres on a molecular tracer called maraciclatide (also known as 99mTc-maraciclatide), developed by the UK-based clinical radiopharmaceutical company Serac Healthcare. The tracer is injected into the patient and designed to bind specifically to a protein called αvβ3 integrin. This protein is selectively upregulated — meaning it is produced in higher quantities — on the surface of blood vessels during angiogenesis, the process by which new blood vessels form. Angiogenesis is a hallmark of inflammatory diseases, and it is essential for the growth and survival of endometriotic lesions. Once the maraciclatide has circulated and attached to these active vessels, a SPECT-CT scan is used to visualise exactly where the tracer has accumulated. The result is a detailed, three-dimensional image of inflamed areas or lesions anywhere in the body, including in the chest cavity — a region conventional scans often miss.
The method is non-invasive, requiring only an injection and a scan, and avoids the need for vaginal examinations, ultrasounds, MRI scans, and the current gold-standard diagnostic procedure: laparoscopy, a surgical operation that involves inserting a camera through a small incision in the abdomen.
What the DETECT trial found
The phase two study, named the “Detecting Endometriosis expressed integrins using technetium-99m” (DETECT) trial, was led by Serac Healthcare and the Nuffield Department of Women’s & Reproductive Health at the University of Oxford. It recruited 20 women with suspected or confirmed pelvic or thoracic endometriosis. Nineteen completed the study, and 17 of those underwent a laparoscopy after their SPECT-CT scan, allowing the team to compare the imaging results directly with surgical findings.
The results, published in The Lancet Obstetrics, Gynaecology & Women’s Health, showed that the new imaging technique was able to detect the presence or absence of endometriosis in 16 out of 19 women — an accuracy rate of 84 per cent. The scans also successfully visualised the condition in 14 of the 17 patients who had endometriosis confirmed through surgery. Notably, no false positives were reported: every woman whose scan indicated endometriosis had it confirmed by the surgeon. The technique proved particularly effective at identifying superficial peritoneal endometriosis, the earliest and most common form of the disease, which accounts for approximately 80 per cent of all endometriosis diagnoses made via laparoscopy. This form is notoriously difficult to spot with ultrasound or MRI. The scans also detected two cases of thoracic endometriosis, a rare and often overlooked variant where endometrial-like tissue grows in the chest cavity.
Professor Christian Becker, co-director of the Endometriosis CaRe Centre in Oxford and co-lead of the study, said: “Novel, non-invasive diagnostic tests for endometriosis are a global research priority. The diagnostic challenge of endometriosis, which presents with varied and non-specific symptoms, is exacerbated by an absence of clinically validated biomarkers and the limitations of currently available imaging techniques.”
Dr Tatjana Gibbons, also of the Nuffield Department of Women’s and Reproductive Health and co-lead of the study, described the findings as “exciting” and said maraciclatide “offers a highly promising diagnostic and monitoring tool, particularly for superficial peritoneal endometriosis, which is the most common and yet the hardest type of endometriosis to identify”. She added: “We are hugely grateful to the patients who have participated in the Detect study without whom investigating this diagnostic approach would not have been possible.”
Towards a transformed future
If these results are confirmed in larger phase three studies — for which Serac Healthcare has already received positive feedback from the US Food and Drug Administration on its trial design, along with FDA Fast Track Designation — maraciclatide imaging could transform clinical practice. Professor Krina Zondervan, co-director of the Endometriosis CaRe Centre and head of the Nuffield Department of Women’s and Reproductive Health, said: “If these results are confirmed in larger phase three studies, imaging with maraciclatide could transform clinical research and practice and potentially empower the development of treatments for women across the globe.”
Beyond diagnosis, the researchers believe the tracer could also be used to monitor disease progression and measure how well patients respond to new therapies, including non-hormonal and immunotherapy options currently under investigation. The DETECT trial remains ongoing, with primary data collection planned for completion in September 2024.
