A new approach to pre-treatment assessment of the N0 neck in oral squamous cell carcinoma: the role of sentinel node biopsy and positron emission tomography

Objectives: Pre-operative staging of the clinically N(0) neck in patients with oral squamous cell carcinoma is hindered by the relatively high false negative/positive rates of conventional imaging techniques. The aim of this study is to evaluate the utility of (18)F-fluoro-deoxy-glucose (FDG) positron emission tomography (PET) and sentinel lymph node (SLN) imaging and biopsy to determine the true disease status of the loco-regional lymphatics.

Methods: Nineteen patients with biopsy proven disease without palpable or radiological evidence of neck metastases underwent pre-operative (18)F-FDG PET and SLN imaging. All patients underwent whole-body FDG PET and a single view of the head and neck. SLN technique was performed using four peri-tumoural injections of (99m)Tc labeled albumin colloid each of 10 MBq. Dynamic and static imaging followed in the antero-posterior and lateral projections. At operation 1 ml of 2.5% Patent Blue Dye and a hand held gamma probe (Neoprobe 1500) were used in combination to identify and remove the SLN. Surgery then continued along conventional lines including a neck dissection. Histology of the resultant specimen was correlated with that of the SLN and pre-operative imaging.

Results: In all patients SLN harvesting was feasible. In 15/19 patients the SLN(s) and the residual neck dissection were -ve for tumour. In 3/19 patients the SLN(s) were +ve for tumour as were other neck nodes. In 1/19 patients the SLN was -ve but another single tumour +ve node was identified in the neck. This patient occurred early in our series with a SLN close to the primary tumour. (18)F-FDG PET failed to identify nodal disease in all four patients with histologically proven lymph node metastases. The size of these nodes ranged from 12 mm x 10 mm x 3 mm to 25 mm x 15 mm x 10 mm.

Conclusion: SLN imaging and biopsy with probe and Patent Blue Dye guided harvest is feasible in patients with oral squamous cell carcinoma and can predict cervical nodal status. (18)F-FDG PET may be less useful.