Time for Consensus on "High-Risk" - Sentinel Lymph Node Biopsy for Cutaneous Squamous Cell Carcinoma: an International Survey of Skin Cancer Specialists and a Literature Update.

There is an urgent need for evidence-based management of cutaneous squamous cell carcinoma (cSCC), particularly "high-risk" tumours. We performed an online survey of skin cancer specialists to assess cSCC research priorities. Respondents were targeted via the international Skin Cancer OUTcomes consortium (SCOUT) and the UK regional Skin Cancer Outcomes North-East (SCONE) research interest group. Thirty-three respondents completed the survey ([46%; 16/33] were non-UK based). 'Defining a role for sentinel lymph node biopsy (SLNB) in high-risk cSCC' was most commonly ranked either 1st or 2nd research priority by respondents (55%; 18/33), with near-total consensus that SLNB could be useful for the early identification of nodal metastasis in high-risk cSCC (97%; 30/31). On this specific research priority, 24 studies with longitudinal follow-up data were identified. Cumulatively, SLNB for cSCC had positivity and false omission rates of 7.0% and 3.1%, respectively, with false negative rates of 29.0%. Given the lack of consensus on a definition of "high-risk" cSCC, it was unsurprising that only two studies of SLNB for head & neck cSCC utilised comparable selection criteria; reporting the highest positivity rates (8.0%) and lowest false-omission rates (2.4%) and false-negative rates (21.4%) overall. There is multi-disciplinary interest in the role of SLNB for "high-risk" cSCC. It appears to perform best in head and neck cases. A consensus definition of "high-risk" cSCC is urgently required to refine the utility of SLNB and guide risk-directed management.