**6. Accuracy in predicting neck status**

The Sentinel European Node Trial (SENT) was a large multicentre European study investigating SLNB in 415 patients with early OCSCC, of which subclinical nodal metastases were identified in 26% of the study population. The findings demonstrated the procedure to be safe, reliable and accurate with a SLN identified in 99% of cases, with 86% sensitivity, 95% negative predictive value and 14% false negative rate [30]. These results have been replicated in other similar studies, albeit with lower false negative rates of 2.56% [22] and 9.1% [31], and with higher rates of contralateral drainage (23–40%) [31, 32].

SLNB allows for identification of unexpected lymphatic drainage patterns, and the SENT trial found that bilateral drainage was identified in 10% of lateralised tumours, and 2.4% had exclusive contralateral drainage. The patients with contralateral drainage, 7 of 49 had positive SLNs, with 5 of the patients draining exclusively contralaterally [30]. The rate of contralateral drainage for lateralised tumours has been documented in other studies to be as high as 23–40% [31, 32].

The detection of contralateral drainage is a major benefit of performing a SLNB as it allows accurate mapping of the lymphatic drainage for each individual patient, and for patients with lateralised tumours with contralateral drainage, these nodes will not be addressed if they undergo a unilateral END. If there were undetected subclinical nodal metastases in these nodes, these patients would then be at risk of a contralateral nodal failure.

The accuracy of SLNB has been further investigated by a systematic review/ meta-analysis assessing the performance of SLNB as a staging procedure for OCSCC and documented it to be reliable with a sensitivity of 88% and specificity of 99%. However, when assessing covariates, performing IHC on the SLN significantly improved the sensitivity to 93% [29]. In addition to the differences in processing of specimens, there was a degree of heterogeneity in the articles in relation to measurement of failure with a combination of END and clinical follow up to detect potential false negatives. Despite this the review demonstrated that SLNB is highly accurate across several different institutions, with an improvement in quality of life including pain, shoulder mobility and scarring when compared to END [29].

## **7. Outcomes following sentinel lymph node biopsy**

A systematic review assessing outcomes in patients with early OCSCC managed with either a SLNB or END found no significant difference in overall survival or disease free survival between the two approaches [33]. This study analysed 5 separate studies with a total of 560 patients and reported 10 more neck recurrences per 1000 patients undergoing the SLNB strategy compared with END, although this was not statistically significant. Conversely SLNB avoided the need for a neck dissection in 64% of patients. While this did demonstrate robust outcomes for patients treated with SLNB, none of the included studies were randomised and as such the overall quality of the evidence was considered low.

Two RCTs have been subsequently published comparing SLNB and END for early OCSCC with both demonstrating equivalent oncological outcomes, and their findings are summarised in **Table 2** and **Figure 7**. The Senti-MERORL trial was a multi-centre RCT with 307 patients that documented a 25% rate of SLN positivity, with these patients proceeding to a neck dissection [15]. There was a mean follow up of 4.95 years, and rates of nodal recurrence were 10.1% in the neck dissection group and 9.3% in the SLNB group, which was not a statistically significant difference. Equivalent locoregional disease control, disease specific survival and overall survival were demonstrated at 2 and 5 years [15]. When looking at the nodal recurrences in patients initially classified as pathologically node negative (pN0), there were 11 patients (10% of the 109 pN0 patients) in the END group and 8 patients (8% of the 99 pN0 patients) in the SLNB group, demonstrating similar rates of nodal staging failure between the two strategies.

A Japanese RCT compared 137 patients in the neck dissection arm and 134 patients in the SLN arm. They found a 34% rate of SLN positivity, and regional recurrence rates were 9.5% and 11.2% in the END and SLNB groups respectively.


#### **Table 2.** *Comparison of two RCTs.*

*Sentinel Lymph Node Biopsy for Early Oral Cavity Squamous Cell Carcinoma DOI: http://dx.doi.org/10.5772/intechopen.99410*

**Figure 7.** *Combined RCT outcomes of nodal recurrence. (Adapted from Garrel et al. [15], Hasegawa et al. [34]).*

This study demonstrated equivalent 3 year overall survival and disease free survival between the END group (87.9% and 81.3%) and the SLN group (86.6% and 78.7%) [34]. Both studies demonstrate high-level evidence to support the use of SLNB as a staging procedure for patients with early T1 or T2 OCSCC.

END has an associated morbidity including shoulder dysfunction, pain and contour changes [16]. Comparison of morbidity associated with SLNB or a neck dissection demonstrates low rates of morbidity overall, however, in one study all the morbidity occurred following neck dissection, with no cases of shoulder dysfunction in the SLNB group [6]. Quality of life assessments demonstrate improved tactile sensitivity and reduced pain sensitivity in the SLNB group, with no significant difference in the presence of lymphoedema although there was trend towards improved symptoms in the sentinel lymph node biopsy group [35]. Functional outcomes were also assessed in the two RCTs, with the Senti-MERORL study finding an initial functional difference between the two groups favouring SLNB at 6 months, however this resolved by 12 months [15]. Hasegawa reported that the END group had persisting inferior scores at 12 months post operatively, when assessing neck stiffness and shoulder dysfunction compared to the SLN group [34].
