Sentinel lymph node biopsy in recurrent and secondary oral cancer after neck dissection: a comparative study with primary tumours

Sentinel lymph node biopsy (SLNB) is a well-established method for managing primary oral squamous cell carcinoma (OSCC), but its role in recurrent or secondary carcinomas, particularly following previous neck dissection, remains insufficiently studied. This study explores the utility of SLNB in these challenging cases, focusing on reliability, sentinel lymph node (SLN) localisation trends, and clinicopathological factors, comparing results between primary and secondary/recurrent carcinomas. A retrospective analysis was conducted on patients with primary and recurrent or secondary OSCCs treated at a German tertiary medical centre. Chi squared tests were used to analyse correlations between clinicopathological characteristics and SLN localisation. The negative predictive value (NPV) was calculated, and the timing of recurrence was also evaluated. We found an NPV of 93.75% for SLNB in primary carcinomas, whereas it was 88.89% for secondary and recurrent carcinomas. While most SLNs were localised ipsilaterally across both groups, recurrent/secondary cancers showed a higher prevalence of contralateral SLNs (22.2%) and bilateral localisation patterns (11.1%) compared to primary carcinomas (8.3% contralateral; 8.3% bilateral). Despite observed trends, no statistically significant associations were found between SLN localisation and clinicopathological factors. The mean (SD) time to recurrence was significantly shorter for primary carcinomas with 9.20 (3.49) months compared to recurrent or secondary cases 32.00 (8.54) months). SLNB in recurrent or secondary OSCC shows distinct SLN localisation patterns, including more contralateral and mixed foci. In terms of NPV, SLNB is reliable in both primary and secondary/recurrent OSCC. Furthermore, a longer recurrence time reinforces the potential of SLNB as a viable alternative to neck dissection in managing these complex cases.