Koos Boeve

80 Chapter 4 is perhaps even more important to select the actual lymph nodes at risk for metastasis, considering the fact that treatment options are limited due to their prior therapy. In this study an overall unexpected drainage pattern was found in 30% of the patients, which was most frequently found after prior radiotherapy (40%) and especially when this was preceded by a neck dissection (88%). In early stage OSCC patients with an untreated neck unexpected drainage patterns were reported in up to 16% in a large multicenter trial [22]. Even though it is well possible to determine individual drainage patterns with the SLNB, one of the disadvantages is to perform an additional neck dissection during a second surgical procedure in case of a positive SLNB procedure. Although improvements a recent review concluded that still no other modality (e.g., ultrasound, CT, MRI and PET-CT) is accurate enough to detect occult metastasis preoperatively in a clinically negative neck reliably [23]. Moreover, posttreatment effects and the high rate of unexpected drainage in pretreated patients might affect the sensitivity of these modalities in detecting occult metastasis. A limitation of the accuracy analysis is the lownumber of metastasis and regional recurrences in our cohort. A possible explanation for these low numbers compared to untreated patients (with an often reported risk of nodal metastases of approximately 25-30%) could be our close follow-up scheme after treatment of their first tumour. Patients in follow-up are potentially earlier diagnosed with recurrent or second primary OSCC, which might cause a relatively high number of early T1 tumours in this cohort. Despite these limitations, this study showed that metastasis appear in early stage local recurrences and second primary tumours. Currently, no guidelines about neck treatment are available for cT1-2N0 OSCC patients with a previously treated neck. In untreated OSCC prognosis was better after an elective neck dissection (of the standard lymph node levels at risk for metastasis) compared to a ‘wait and see’ policy [24]. Because of the aberrant drainage patterns, we advocate to use the SLNB also in patients with early stage second primaries or local recurrences to select patients who might benefit from treatment of the neck . However, more extensive research is needed to confirm that this strategy actually improves the prognosis of these patients. CONCLUSION SLNB seems to be a reliable procedure for neck staging of cT1-2N0 OSCC patients with a previously treated neck. Moreover, SLNB determines the individual lymphatic drainage patterns, enabling visualization of drainage pattern variability in 30% of these patients.