Practice variation in defining sentinel lymph nodes on lymphoscintigrams in oral cancer patients.

PURPOSE: Lymphoscintigraphic imaging and adequate interpretation of the lymphatic drainage pattern is an essential step in the sentinel lymph node biopsy (SLNB) procedure. In oral cancer, identification of the sentinel lymph node (SLN) can be challenging. In this study, interobserver variability in defining SLNs on lymphoscintigrams was evaluated in patients with T1-T2 stage N0 oral cancer. METHODS: Sixteen observers (head and neck surgeons, nuclear medicine physicians or teams of both) from various institutes were asked which criteria they use to consider a hot focus on the lymphoscintigram as SLN. Lymphoscintigrams of 9 patients with 47 hot foci (3-9 per patient) were assessed, using a scale of 'yes/equivocal/no'. Bilateral drainage was seen in four of nine cases. In three cases additional late single photon emission computed tomography (SPECT)/CT scanning was performed. Interobserver variability was evaluated by kappa (к) analysis, using linear weighted pairwise comparison of the observers. Conservative (equivocal analysed as no) and sensitive (equivocal analysed as yes) assessment strategies were investigated using pairwise kappa analysis. RESULTS: Various definitions of SLN on lymphoscintigrams were given. Interobserver variability of all cases using a 3-point scale showed fair agreement (71%, к(w) = 0.29). The conservative and sensitive analyses both showed moderate agreement: conservative approach к = 0.44 (in 80% of the hot foci the observers agreed) and sensitive approach к = 0.42 (81%) respectively. Multidisciplinary involvement in image interpretation and higher levels of observer experience appeared to increase agreement. CONCLUSION: Among 16 observers, there is practice variation in defining SLNs on lymphoscintigrams in oral cancer patients. Interobserver variability of lymphoscintigraphic interpretation shows moderate agreement. In order to achieve better agreement in defining SLNs on lymphoscintigrams specific guidelines are warranted.