Page 35 - Sentinel lymph node biopsy in oral cavity cancer - Inne J. den Toom

INTRODUCTION One of the most important prognostic factors in T1-T2 oral squamous cell carcinoma is the presence of nodal metastases in the neck.1,6 Clinical staging by palpation followed by imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound-guided fine-needle aspiration cytology (USgFNAC) does 2 not seem reliable enough to detect early nodal metastases, because occult (micro) metastases are still present in about 30% of the node negative (cN0) patients.2,5-15 According to Weiss et al. a risk more than 20% of occult metastases warrants elective neck dissection (END), although leading to overtreatment in up to 80% of patients.16 A wait and scan policy may also be proposed in selected cases, since delayed lymph node metastases may still be cured by salvage surgery. However, this strategy means more extended neck dissection (ND) and more often adjuvant radiotherapy for patients with delayed metastases as compared patients with occult metastases undergoing END.17 With both strategies some patients are unnecessarily overtreated.18,19 Therefore, more reliable staging procedures are desirable. Sentinel lymph node biopsy (SLNB) is a reliable diagnostic procedure for staging of the cN0 neck and identifying patients with nodal metastatic disease.14,20,24 First, studies analysed the value of SLNB assisted neck dissection, considering a ND as the reference (gold) standard.25,26 However, follow-up (no ND if SLNB is negative) is a more representative reference standard than (routine) histopathological examination of (elective) neck dissections.27 The standard SLNB procedure starts with peritumoural injection of a [99mTc]Tc-labelled colloidal tracer, drainage mapping by lymphoscintigraphy (LSG) and the injection of blue dye intraoperatively. Radioactive, as detected by a gamma probe, and/or blue lymph nodes are harvested during a surgical procedure. Using step-serial sectioning and immunohistochemistry as histopathological evaluation it is possible to detect micrometastases and isolated tumour cells (ITC) with higher sensitivity compared to traditional histopathological evaluation after END.12 When used routinely in clinical practice SLNB positive diagnosed patients undergo an subsequent ND, while patients with a negative SLNB are carefully observed, without the disadvantage of undergoing unnecessary surgery. 33