Multimodality nanotracer to improve detection of sentinel nodes in oesophageal cancer

Objectives Early oesophageal cancer can now be treated with endoscopic resection, however accurate methods of staging lymph nodes preoperatively remain elusive. To improve detection of sentinel lymph nodes, 99m-technetium (99mTc) labelled super paramagnetic iron oxide nanoparticles (SPIONs) were evaluated in a swine model.

Methods An initial study was undertaken on nine swine, with injection of either 30nm SPION or 99mTc-SPION into the hind limbs, followed by assessment with magnetic resonance imaging (MRI). In the second study, 4 swine were injected with 99mTc-SPION into the oesophagus, and pre- and post-injection MRI images were acquired. Sentinel nodes were identified using a gamma probe. Finally, bio distribution of the tracer was evaluated with injection of 99mTc-antimony trisulphide colloid (ATC) and 99mTc-SPIONs, respectively.

Results In the hind limb study, clear uptake of SPIONs and 99mTc-SPIONs were seen in sentinel nodes on MRI imaging. In the SPION alone group, uptake was confirmed in all blue lymph nodes. In the 99mTc-SPION group, uptake of the tracer was confirmed on surgical exploration, with the gamma probe detecting all nodes seen on MRI imaging. Radiolabelling efficiency was >98%. In the oesophageal study, MRI images confirmed uptake of SPIONs to the celiac lymph nodes. Bio distribution of 99mTc-ATC and 99mTc-SPIONs were similar, with the exception of the kidneys.

Conclusions A multimodality tracer comprised of 99mTc-SPIONs was prepared and validated using both MRI imaging and gamma probe. This new tracer could allow preoperative evaluation of sentinel lymph nodes in patients with early oesophageal cancer, and guide treatment decisions.