Intraoperative sentinel node imaging versus SPECT/CT in oral cancer - A blinded comparison

Sentinel node biopsy (SNB) is gaining popularity as a staging tool in oral cancer. Protocol mandates radiotracer injection and pre-operative imaging (LSG ± SPECT/CT) in the nuclear medicine department. This approach limits application to accessible tumours and to centres with nuclear medicine. New technology, freehand single photon emission computed tomography (fhSPECT), has proved a useful adjunct in intraoperative imaging and localisation of sentinel nodes. This study investigates fhSPECT as an alternative to traditional imaging, an approach that would widen the remit of SNB.

Fifty consecutive cT1-T2 N0 oral cancer patients received radiotracer followed by lymphoscintigraphy and SPECT/CT. Surgery was undertaken using fhSPECT by a surgeon blinded to pre-operative imaging. Prior to biopsy completion, results of pre-operative imaging were reviewed and any additional nodes removed. The accuracy of LSG, SPECT/CT and fhSPECT were compared.

Nineteen patients had positive sentinel nodes. Disease free survival for sentinel node positive versus negative was significant (p < 0.005). All modalities missed positive nodes in at least one patient. The false negative rate for lymphoscintigraphy, SPECT/CT and fhSPECT was 26.3%, 15.8% and 5.3% respectively.

These data show a surgeon naïve to the results of traditional pre-operative sentinel node imaging can use fhSPECT in the operating theatre to accurately locate sentinel nodes in oral cancer. Freehand SPECT showed excellent sensitivity and a low false negative rate offering the possibility of a streamlined intraoperative sentinel node protocol.