Background and objectives: One potential barrier to the wide adoption of SNB is a false negative rate of up to 13% which is likely to be due to the incorrect identification of the sentinel node at surgery. A new navigational tool allows for intraoperative ‘free-hand SPECT’ to produce a 3D image of the sentinel nodes during surgery, and may therefore improve the accuracy of the lymph node sampling.
Methods: From December 2012 prospective data was collected on a case series of 20 patients undergoing navigational SNB. Pre-operative lymphoscintigraphy using 99mTc-Nanocolloid at an average dose of 60 MBq was performed up to 24 h prior to surgery. At operation a hand held gamma probe tracked by infrared detection was used to build up a pattern of isotope hot spots which was then projected onto a video image of the patient, directing the surgeon to the correct location for node retrieval.
Results: SNB was successfully performed in all patients (1 melanoma, 2 parotid tumours and 17 tumours of the oral cavity). The SNB was positive for metastasis in 4 cases (20%). In 10 cases sentinel nodes were identified at surgery which has not been detected by pre-operative screening, including intraparotid lymph nodes draining a parotid malignancy. Of the four cases with positive sentinel nodes one was in a node which had not been identified by pre-operative lymphoscintigraphy. There have been no recurrences at the early stages of follow up.
Conclusions: We have demonstrated that navigational surgery aids the retrieval of sentinel lymph nodes. In the future it will be possible to perform a one stage procedure with intra-operative injection of 99mTc-Nanocolloid. This will cut the cost of the procedure and allow its use in different tumour sites such as tongue base, tonsil and larynx.
Key words: sentinel node biopsy; 3D navigation surgery; lymphoscintigraphy