Magnetic Tracer Shows Promise for Mapping Sentinel Lymph Nodes in Early Ovarian Cancer

A small pilot study from the Netherlands suggests that a magnetic tracer already used in breast cancer surgery may offer a radioactive-free way to find the sentinel lymph nodes of women undergoing surgery for suspected early-stage epithelial ovarian cancer. The research, led by Pim Laven and colleagues at Maastricht University Medical Centre and published in the Journal of Ovarian Research, tested the iron-oxide-based agent Magtrace in a cohort of sixteen eligible patients, of whom ten ultimately received tracer injections during open abdominal surgery. Although the numbers are modest and the results preliminary, the study adds an intriguing data point to a long-running effort to make lymph node assessment in ovarian cancer less invasive, less radioactive, and better suited to the realities of the operating theatre.

The sentinel lymph node concept rests on a simple anatomical insight: when a tumour begins to spread, cancer cells do not scatter randomly through the lymphatic system. Instead, they travel first to one or a few nearby lymph nodes, the so-called sentinel nodes, which act as the initial filters on the drainage pathway. If surgeons can identify and remove precisely those nodes, pathologists can examine them closely for metastatic cells, and the wider lymphatic basin can be left intact when they are clean. This spares patients the morbidity of extensive lymph node dissection, which in the pelvis and para-aortic region can include lymphedema, lymphoceles, vascular injury, and prolonged recovery. Sentinel node biopsy has transformed the management of breast cancer and melanoma, and it is increasingly applied in endometrial and cervical cancer as well.

Ovarian cancer, however, has proven a harder target. The lymphatic drainage of the ovary is unusually complex, following the ovarian vessels upward along the infundibulopelvic ligament toward para-aortic nodes high in the retroperitoneum, while parallel pathways drain through the broad ligament to pelvic nodes along the iliac vessels. This dual drainage means that sentinel nodes in ovarian cancer can appear on both sides of the body and at considerable distance from the tumour, making reliable identification technically demanding. Moreover, most patients with ovarian cancer are diagnosed at advanced stages, when the disease has already spread beyond the ovary and full surgical staging with systematic lymphadenectomy is standard. It is in the smaller group of patients with apparently early-stage disease, where the distinction between stage I and stage III hinges on whether lymph nodes contain microscopic deposits, that a minimally invasive sentinel node approach would be most valuable.

The standard technique for sentinel node detection in ovarian cancer combines a radioactive tracer, technetium-99m radiocolloid, with a visual agent such as blue dye or indocyanine green, a fluorescent compound that glows under near-infrared light. The radiocolloid is injected near the tumour, drains to the sentinel nodes, and is located intraoperatively with a handheld gamma probe that clicks as it approaches the radioactive signal. Studies have shown this combination to be feasible, but each component carries practical drawbacks. Technetium-99m requires coordination with a nuclear medicine department, involves radiation exposure for patients and staff, and is subject to regulatory and logistical constraints that limit its availability in many hospitals, particularly in low-resource settings. Blue dye carries a small risk of anaphylaxis and can permanently tattoo the skin, while indocyanine green requires specialized near-infrared imaging equipment that works well through tissue only to a limited depth.

These limitations are especially acute in ovarian cancer surgery, which is typically performed by laparotomy, a large open abdominal incision, rather than by minimally invasive laparoscopy. Fluorescent tracers such as indocyanine green excel in laparoscopic procedures, where the camera system integrates the infrared imaging, but in an open surgical field the fluorescence can be difficult to visualize under standard operating room lighting, and the signal may be washed out by ambient light or obscured by tissue and blood. A tracer that could be detected with a simple handheld probe, without radiation and without dependence on optical conditions, would fit the open-surgery environment far more naturally. This is the gap that Magtrace is designed to fill.

Magtrace is a suspension of superparamagnetic iron oxide particles, micrometre-scale carriers loaded with even smaller iron oxide cores. Once injected into the tissue near the tumour, the particles are taken up by lymphatic vessels and carried to the regional lymph nodes, where they accumulate and impart a characteristic brown discoloration that surgeons can see directly. More importantly, the particles distort a local magnetic field in a way that a handheld device called the Sentimag probe can detect. The probe, which resembles a modified magnetometer, is passed over the surgical field and produces an audible and visual signal whose strength increases as it nears the magnetized tissue, allowing the surgeon to home in on the sentinel node much as a gamma probe tracks radioactivity. Because the magnetic signal is not attenuated by tissue in the way light is, and because it involves no ionizing radiation, the technique can in principle be used in any operating room without nuclear medicine support.

In the Maastricht study, the researchers injected both Magtrace and technetium-99m into the same anatomical structures, the ligamentum ovarii proprium, which connects the ovary to the uterus, and the infundibulopelvic ligament or its stumps, through which the ovarian vessels run toward the para-aortic region. Injecting both tracers at the same sites allowed a direct head-to-head comparison: after an interval of at least fifteen minutes, the surgical team located sentinel nodes using the Sentimag probe for the magnetic tracer and a gamma probe for the radiocolloid. The dual-tracer design is a common strategy in pilot studies of new tracers, because it lets investigators measure how often the new agent finds the same nodes as the established one, and whether it finds any nodes the standard technique misses.

The patient cohort illustrates the practical complexities of studying early ovarian cancer. Of the sixteen patients enrolled, ten actually received the tracer injections, nine during primary surgery for suspected ovarian cancer and one during secondary staging after a previous tumour resection had already confirmed the disease. Among the nine primary surgery patients, frozen-section analysis, the rapid microscopic examination of tissue performed while the patient is still on the operating table, revealed that six actually had benign or borderline tumours rather than invasive carcinoma, so the sentinel node procedure was not clinically relevant for them. That left three patients with confirmed epithelial ovarian cancer undergoing primary staging, and in all three the procedure succeeded, with at least one sentinel node identified using Magtrace. In the single patient who underwent mapping during secondary staging, the procedure was unsuccessful, a failure the authors note may relate to the altered anatomy and scar tissue left by the prior surgery, which can disrupt lymphatic drainage pathways.

The investigators conclude that Magtrace injection shows promise for sentinel node detection in epithelial ovarian cancer, while emphasizing that larger studies are needed to confirm its value. That caution is warranted. With only three successful primary staging cases, the study cannot establish detection rates, sensitivity, or false-negative rates, the metrics that ultimately determine whether a sentinel node technique is safe to rely on in clinical practice. The high proportion of benign frozen-section results also highlights a recurring challenge in this field: preoperative imaging often cannot reliably distinguish early ovarian cancer from benign masses, so trials of staging techniques must enroll generously and expect a substantial fraction of participants to fall outside the target diagnosis. The single failure in secondary staging likewise suggests that the technique’s role may be limited to primary surgery, at least initially.

Nevertheless, the study points toward a plausible future in which ovarian cancer staging becomes less burdensome. A magnetic tracer that works in open surgery, requires no radioactive material, and leaves a visible brown mark on the sentinel nodes could make sentinel node biopsy accessible to surgical teams worldwide who lack nuclear medicine infrastructure, and could simplify logistics for centres that do. Before that future arrives, the technique will need validation in larger prospective cohorts, ideally comparing Magtrace directly against the established radiocolloid and fluorescence combinations and following patients long enough to confirm that a negative sentinel node truly predicts the absence of regional metastases. For now, the Maastricht pilot offers an early but encouraging signal that the magnetic approach, so successful in breast cancer, may find a place in one of gynaecologic oncology’s most technically stubborn frontiers.

Subject of Research: Sentinel lymph node detection using the magnetic tracer Magtrace in early-stage epithelial ovarian cancer

Article Title: Magtrace as tracer for sentinel lymph node detection in early stage epithelial ovarian cancer: a pilot study

Article References: Laven, P., van der Pol, J. A. J., Slangen, B. F. M., Kruitwagen, R. F. P. M., & Lambrechts, S. (2026). Magtrace as tracer for sentinel lymph node detection in early stage epithelial ovarian cancer: a pilot study. Journal of Ovarian Research. https://doi.org/10.1186/s13048-026-02297-2

Image Credits: AI Generated

DOI: 10.1186/s13048-026-02297-2

Keywords: ovarian cancer, sentinel lymph node, Magtrace, magnetic tracer, superparamagnetic iron oxide, Sentimag, technetium-99m, indocyanine green, laparotomy, surgical staging, gynaecologic oncology, pilot study