New Delhi: For millions of women worldwide, the journey to an endometriosis diagnosis is not a medical process—it is an ordeal. Years of debilitating pain, dozens of hospital visits, and test after test that appears normal, until a surgeon finally peers inside with a camera and confirms what the patient always suspected.
A new study published in The Lancet Obstetrics, Gynaecology & Women’s Health suggests that this long, invasive path to diagnosis may one day be shortened by a radioactive tracer injected into the bloodstream.
The Phase 2 trial, conducted by researchers at the University of Oxford and published Thursday, tested a molecular imaging agent called 99mTc-maraciclatide on 20 patients with suspected or confirmed endometriosis.
The agent correctly identified disease in 14 of 17 surgically confirmed cases—including lesions that had been invisible on prior ultrasounds and MRIs. It produced no false positives. If the results hold in larger trials planned for later this year, the procedure could offer the first reliable, non-invasive way to detect the earliest and most common form of the disease.
“These exciting findings indicate that 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,” said Dr Tatjana Gibbons, lead author of the paper and investigator at the Nuffield Department of Women’s and Reproductive Health, University of Oxford.
Why an Endometriosis diagnosis takes time
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus—most commonly in the pelvis, but sometimes in the lungs, the bowel, or other organs. Responding to the same hormonal cycles as the uterus, this tissue swells and bleeds every month—except the blood has nowhere to go. The result is chronic inflammation, scarring, and adhesions that can fuse organs together.
The symptoms are wide-ranging and frequently mistaken for other conditions. For instance, severe menstrual cramps that don’t respond to painkillers, chronic pelvic pain, pain during intercourse, painful urination or bowel movements, and, in advanced cases, infertility. Some women also experience fatigue, bloating, and, in rare cases of thoracic endometriosis, even chest pain or coughing up blood during periods.
“Sadly enough, we have nothing in allopathy to reverse endometriosis,” said Dr Uma Vaidyanathan, Director of Obstetrics and Gynaecology at Fortis Hospital, New Delhi. “The only tools available are hormonal therapy to slow its progression, and surgery to physically remove lesions—each with its own limitations and risks,” she added.
Globally, it affects roughly 190 million women worldwide, or about one in 10 women of childbearing age. India is known to represent 25 per cent of the global burden, with an estimated 43 million women suffering from it. Despite the prevalence, women typically wait 8 to 12 years before receiving a confirmed diagnosis.
The delay is not without reason. Dr Anshumala Shukla Kulkarni, Head, Minimally Invasive Gynaecology, Gynaecology, Laparoscopic and Robotic Surgery at Kokilaben Dhirubhai Ambani Hospital in Mumbai, explained that endometriosis presents in three forms, and two of them are relatively detectable.
The first one is ovarian endometriomas—cysts filled with old blood—that show up clearly on standard ultrasounds. Second, deep infiltrative endometriosis, which invades other organs beyond 5 millimetres, and can be spotted on transvaginal ultrasound or Magnetic Resonance Imaging (MRI).
The problem, she explained, lies with the third type, the Superficial Peritoneal Endometriosis (SPE). These are tiny lesions, sometimes just 3 to 4 millimetres, scattered across the lining of the pelvis. They are found in 80 per cent of all laparoscopically diagnosed diseases, making them the most prevalent subtype—and yet they are essentially invisible to conventional imaging.
“Ultrasound doesn’t show anything, MRI doesn’t show anything, but the patient has all the symptoms,” said Dr Kulkarni. “These patients get told it’s PCOD (Polycystic Ovarian Disease), it’s stress—until the disease has progressed significantly,” she added.
It is precisely this diagnostic blind spot that the new study targets.
How the radioactive tracer works
The new imaging agent works by taking advantage of a unique feature of endometriotic lesions.
As these tissue patches grow, they release signals that cause new blood vessels to form. This process is called angiogenesis. These vessels are marked by elevated levels of specific proteins called integrins, particularly the alpha-v beta-3 variety.
Maraciclatide, a dye-like tracer, binds with these integrins. Tagged with a radioactive element and injected intravenously, the dye travels through the bloodstream, concentrates in areas of active angiogenesis, and makes them visible on a SPECT-CT scan. A SPECT-CT (Single-Photon Emission Computed Tomography–Computed Tomography) scan is an imaging test that combines two techniques—one that shows how the body is functioning (such as blood flow or metabolism) and another that provides detailed anatomical images. Together, they help doctors diagnose and monitor conditions in the heart, brain, and bones.
“Endometriosis lesions tend to have increased blood vessel formation. This means they have a greater blood supply, so some proteins are more visible in them. When the dye is injected, it concentrates in those areas and becomes visible on imaging,” explained Dr Vaidyanathan.
However, the concept isn’t entirely new. Similar tracers are already used in cancer detection and in inflammatory conditions like rheumatoid arthritis. What this study established, as Dr Kulkarni put it, is the correlation: “The integrin exists, there is nothing new. The tracer also existed. They have basically found the association”—and then matched scan findings with laparoscopy results, with nearly 98 per cent accuracy.
Promising, but early days
Maraciclatide has not been approved by the US Food and Drug Administration or any other regulatory body, though it has received an FDA Fast Track designation. Phase 3 multi-centre international trials are planned for later this year.
According to the authors, side effects appear minimal. The radiation dose is comparable to other nuclear medicine scans used in cardiology and oncology, making it safe for occasional use—though not for routine annual monitoring.
“Maybe once or twice in a lifetime to make certain key decisions, it’s safe to do,” said Dr Kulkarni.
Doctors that ThePrint spoke to explained what this could mean for endometriosis management.
Dr Vaidyanathan described it as “very, very early days”, noting that endometriosis management remains entirely clinical for now, with no approved drug to reverse the disease and surgery reserved for select cases only.
Dr Kulkarni said that even if the tracer performs well in Phase 3 trials, its value will depend on its use. She pointed to a specific scenario where the tool would matter most.
“A young patient, 15 or 17 years old, with clear symptoms but nothing on any scan. Without visible proof, families are often reluctant to start hormonal therapy, and the disease is quietly allowed to advance. If the tracer is used, the patient and the mother both will know convincingly that they should start medical management properly, so that we don’t allow the endometriosis to grow,” she said.
Early detection and timely excision, she added, could prevent the disease from progressing to its more destructive, fertility-destroying forms and spare patients the cycle of repeat surgeries that advanced endometriosis so often demands.
(Edited by Viny Mishra)
Also read: Endometriosis, dismissed as ‘period pain’, must be prioritised as women’s health issue, says study