SPECT/CT-guided lymph drainage mapping for the planning of unilateral elective nodal irradiation in head and neck squamous cell carcinoma.

Purpose: To investigate the feasibility of lymph drainage mapping (LDM) using SPECT/CT to help select head and neck cancer (HNSCC) patients for unilateral elective neck irradiation (ENI). Patients with lateralized HNSCC treated with radiotherapy routinely undergo bilateral ENI, despite the incidence of contralateral regional failure being relatively low even after unilateral ENI. We hypothesized that patients with a lateralized tumor without visible lymph drainage to the contralateral neck have an extremely low risk of contralateral involved nodes. Excluding the contralateral neck from elective irradiation will reduce radiation-induced toxicity and improve quality-of-life.

Methods: Fifty-five patients with lateralized cT1-3N0-2bM0 HNSCC not crossing the midline underwent LDM. Radiolabeled Tc-nanocolloid was injected in 4-5 depots around and in the primary tumor. Lymph drainage patterns were visualized using planar scintigraphy and SPECT/CT after 4 h. We report on the incidence of contralateral drainage, the location of draining areas, and the size of underlying nodes.

Results: Lymphatic drainage was successfully visualized in 54 patients (98%). In 11 patients (20%) with visible contralateral drainage, 14 draining areas (16 nodes; median volume 0.50 cc, diameter 8.0 mm) were identified. Neck levels with contralateral drainage were level II (88%), III (25%), and IV (13%). Contralateral drainage was significantly higher in T3 compared to T1-2 tumors (45 and 14%, respectively, P = 0.035).

Conclusion: SPECT/CT-guided LDM is feasible and can be used to guide unilateral ENI in HNSCC patients in prospective studies. In addition, the anatomical confidence in visualization of contralateral drainage indicates a potential for ENI limited to draining levels alone.