Reliable evaluation of lymphatic metastases is essential in many pediatric solid tumors, allowing for accurate diagnostic staging and determination of appropriate therapeutic regimens. Few studies examining the safety and utility of sentinel lymph node biopsy (SLNB) in pediatric patients have been performed, particularly with newer targeted lymphatic agents. The purpose of this study was to prospectively evaluate the safety and tolerability of the SLN radiotracer 99mTc‑tilmanocept (LYMPHOSEEK®, Cardinal Health), a technetium-based agent uniquely targeted to CD206 receptors in lymph nodes, for pediatric patients with solid tumors.
A prospective, open-label, within-subject trial was approved by the Food and Drug Administration (FDA) and the Institutional Review Boards at all participating institutions. Enrolled patients received 50-mcg tilmanocept radiolabeled with 0.5-mCi 99mTc, 15 minutes to 8 hours before SLNB procedure. Safety measurements included collection of adverse events, vital signs, clinical labs, and ECGs. Preoperative lymphoscintigraphy was obtained and/or vital blue dye administered at the discretion of the surgeon. Patients underwent SLNB identification and removal of identified nodes utilizing a handheld gamma probe. Excised nodes underwent histopathology evaluation per institutional SLN protocols and cooperative group central review.
Twenty-four eligible patients (5-melanomas, 5-rhabdomyosarcomas, 12-nonrhabdomyosarcoma soft tissue sarcomas, 2-others; 15-females; mean age 11.6±4.9 years) were enrolled over 3.5 years, with early closure requested by FDA due to meeting primary objective. No patient experienced adverse events attributed to 99mTc‑tilmanocept. 99mTc‑tilmanocept identified SLNs in 96% of patients, with a mean of 3.3±3.1 SLNs/patient. Two patients (1-melanoma, 1-rhabdomyosarcoma) had pathology-positive SLNs, both successfully identified by 99mTc‑tilmanocept.
In this feasibility and safety study, 99mTc‑tilmanocept demonstrated high SLN localization with excellent safety profile in pediatric patients. Although the sample size was small, these results suggest that 99mTc‑tilmanocept appears to be safe and effective in identifying SLNs, with fast transit and minimal pain, in pediatric solid tumors.