Abstract
Approximately 70–80% of patients with cT1-2N0 oral squamous cell carcinoma (OSCC) ultimately prove to have no cancer in the cervical lymphatics on final pathology after selective neck dissection. As a result, sentinel lymph node biopsy (SLNB) has been adopted during the last decade as a diagnostic staging method to intelligently identify patients who would benefit from formal selective lymphadenectomy or neck irradiation. While not yet universally accepted, SLNB is now incorporated in many national guidelines. SLNB offers a less invasive alternative to elective neck dissection (END), and has some advantages and disadvantages. SLNB can assess the individual drainage pattern and, with step serial sectioning and immunohistochemistry (IHC), can enable the accurate detection of micrometastases and isolated tumor cells (ITCs). Staging of the neck is improved relative to END with routine histopathological examination. The improvements in staging are particularly notable for the contralateral neck and the pretreated neck. However, for floor of mouth (FOM) tumors, occult metastases are frequently missed by SLNB due to the proximity of activity from the primary site to the lymphatics (the shine through phenomenon). For FOM cancers, it is advised to perform either elective neck dissection or superselective neck dissection of the preglandular triangle of level I. New tracers and techniques under development may improve the diagnostic accuracy of SLNB for early-stage OSCC, particularly for FOM tumors. Treatment of the neck (either neck dissection or radiotherapy), although limited to levels I–IV, remains mandatory for any positive category of metastasis (macrometastasis, micrometastasis, or ITCs). Recently, the updated EANM practical guidelines for SLN localization in OSCC and the surgical consensus guidelines on SLNB in patients with OSCC were published. In this review, the current evidence and results of SLNB in early OSCC are presented.
Highlights
Cervical lymph node metastasis is the single most important prognostic factor in oral squamous cell carcinoma (OSCC), and accurate detection of cervical lymph node metastases is critical for surgical and adjuvant therapy planning
Palpation has a low sensitivity in detecting lymph node metastases and proved to be inferior compared to conventional imaging techniques, such as ultrasonography (US), computerized tomography (CT) and magnetic resonance imaging (MRI) and Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG PET)
In a series of 488 cT1-2N0 OSCC patients, sentinel lymph node biopsy (SLNB) had a lower sensitivity in floor of mouth (FOM) tumors than in non-FOM locations: 63% and 86% (p = 0.008), respectively [19]
Summary
Cervical lymph node metastasis is the single most important prognostic factor in oral squamous cell carcinoma (OSCC), and accurate detection of cervical lymph node metastases is critical for surgical and adjuvant therapy planning. In the largest multicenter study of 415 cT12N0 OSCC patients, a sensitivity of 86% and NPV of 95% were found for SNLB to detect occult lymph node metastasis (incidence 26%) after 3-year follow-up [14]. In the latter European SENT trial, all participating centers had to complete at least ten successful training SNLB procedures (validated against neck dissection) prior to recruiting to SENT. In a study on the topographical distribution of SLNs and non-SLN metastases in 220 patients with early-stage OSCC and lymph node metastases, 53 patients had positive SLNB and underwent subsequent neck dissection. Large registries may be helpful to further improve these guidelines in the near future
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