Page 100 - Sentinel lymph node biopsy in oral cavity cancer - Inne J. den Toom

Chapter 5 measuring from the mucosal line, which is mostly described as method for measuring the DOI. However, this is more for theoretical than practical purposes assuming the small thickness of healthy epithelium, so still reliable comparisons between both measurements could be made. Although both meta-analyses conclude that DOI correlates with regional lymph node involvement, they did mention different study groups, measurement techniques and cut-off values, which hamper good comparison between these studies.8,9 Both studies found a wide range for cut-off values of 1.5-10 mm, with a most optimal cut-off value of 4 mm in the meta-analysis of Huang et al.8 A recent large study of 469 patients, which was published after both meta-analyses, used also a cut-off value of 4 mm to show an association between DOI and nodal involvement, though with poor sensitivity and specificity.12 The optimal cut-off value found in our study (3.4 mm) is close to this value. However, still 15% of our patients below this 3.4 mm cut-off value showed regional metastases. Therefore, in our opinion SLNB should be offered to all patients, also those with limited DOI tumours (Figure 3). Other studies using a ROC analysis to determine this optimal cut-off value found comparable values, i.e. 4 mm and 4.59 mm.5,19 The study of Goerkem et al. using this analysis did not found an optimal cut- off value.20 That study and our present one are the only studies that use SLNB-alone as reference standard. In 78 patients Goerkem et al. found an average DOI of 6.45 mm, with an area under the curve of 0.54 in the ROC analysis, concluding that DOI (and separately also tumour thickness) should not be used for assessment of elective treatment of the neck. Moreover, they suggested that SLNB should be used in all early stage oral cavity carcinomas with a cN0 neck.20 In another study, by Alkureishi et al., with SLNB (and SLNB-assisted neck dissection) as reference standard a considerable heterogeneity in study groups has to be taken into account when comparing the results with the present study. In this study patients with cT3-T4 tumours and oropharyngeal tumours were included as well.37 They analyzed a cohort of 172 patients of whom 134 patients had oral tumours with a mean DOI of 7.3 mm. Patients underwent SLNB alone or SLNB-assisted neck dissection, however the number of cases in both groups is unfortunately not reported. This may be important because histopathological examination of a neck dissection specimen is a suboptimal reference standard as compared to watchful waiting. They found nodal metastases in 41% of patients and demonstrated that in both oral and oropharyngeal cancer tumour depth reached a stronger correlation with nodal metastases than T-classification. The most optimal cut-off value for oral cavity cancer alone in their cohort was 4 mm 98