This pilot study evaluates the feasibility of 68Ga-tilmanocept PET/CT for SLN mapping in patients with endometrial cancer.

Rationale: Currently, the use of indocyanine green (ICG) is the most widely accepted sentinel lymph node (SLN) mapping technique in endometrial cancer but the acquired SLN detection rates greatly vary. We propose that adding preoperative imaging with the radiotracer Gallium-68-tilmanocept (68Ga-tilmanocept) PET/CT can further improve SLN mapping in patients with endometrial cancer and reliably guide the surgeon towards the true SLN intraoperatively.

Objective: To evaluate the feasibility of sentinel lymph node imaging with 68Ga-tilmanocept PET/CT.

Study design: Non-randomised, single-centre, single-arm pilot study in the UMC Utrecht.

Study population: Patients with clinically stage I-II high/high-intermediate risk endometrial cancer scheduled for robot-assisted pelvic and para-aortic lymphatic staging (including SLN procedure). A total of 10 patients will be included.

Intervention (if applicable): Preoperative cervical injection of 68Ga-tilmanocept followed by preoperative PET/CT imaging (in adjunct to the standard-of-care: intraoperative injection with indocyanine green (ICG) with real-time near-infrared (NIR) fluorescence imaging). Injection of 68Ga-tilmanocept is performed by the gynaecologist in an outpatient setting. The PET/CT (PET + contrast enhanced CT abdomen) will be performed 30-90 minutes after tracer injection.

Main study parameters/endpoints: Feasibility of 68Ga-tilmanocept PET/CT for SLN mapping, which is evaluated by its SLN detection rate.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Extra burden for subjects concerns an additional site visit for cervical injection followed by PET/CT imaging with a total duration of two hours (including waiting time of ~60 minutes). The preoperative injection with 68Ga-tilmanocept while patient is awake adds minimal discomfort to the patient. The extra administration of 10 MBq 68Ga-tilmanocept followed by PET/CT, resulting in a radiation of 6.3 mSv, is considered an acceptable radiation burden to the subjects. Adverse reactions after injection of radiolabelled tilmanocept rarely occur. No additional blood samples, follow-up visits or physical examinations are needed during this study. The additional site visit does not delay the scheduled standard care.

Subjects may benefit from this study since the SLN detection rate could be increased and/or faster by adding 68Ga-tilmanocept PET/CT to the diagnostic procedure.

Inclusion Criteria:

• Clinical FIGO 2012 stage I-II high/high-intermediate risk endometrial cancer;
• Scheduled for robot-assisted full pelvic and para-aortic staging;
• Age ≥18 years and able to provide informed consent.

Exclusion Criteria:

• Pregnancy or current breastfeeding;
• Prior severe allergic reaction to iodine;
• Severe renal insufficiency (stage 3 or 4);
• Clinical or radiological evidence of metastatic disease.