Presentation Authors: Delia Toomey*, Sylvia Yan, Jade Harrison, Michael Ager, James Pilcher, Sue Heenan, Benjamin Ayres, London, United Kingdom, Simon Horenblas, Amsterdam, Netherlands, Nicholas Watkin, London, United Kingdom
Introduction: The role of dynamic sentinel inguinal node biopsy (DSNB) in the staging of intermediate and high risk cN0 squamous carcinoma of the penis (SCCp) is established. However, variability in sensitivity and concern over false negative studies has limited the adoption of the technique worldwide. There is also a need to establish an acceptable non-visualisation rate (N-VR) for tracer uptake for quality assurance of a unit. For these reasons, we evaluated our prospective cohort to determine whether there is a learning curve and establish a bench mark for N-VR.
Methods: A prospective study of DSNB in our unit has been undertaken from 2003-2018. Regular review, of NV-R of inguinal basins and close monitoring of false negative study outcomes has been performed. At the onset of the study, the unit had not performed any mentored procedures but had adopted the technique, collaborating with a high volume unit. The nuclear medicine department had considerable experience with other tumour DSNB procedures. The methodology has remained unchanged with the same dosage and site of injection of nannocolloid, gamma probe, image reporting, surgical approach, surgical team and histological reporting throughout. We have analysed the incidence of our false negative procedures and any variation in N-VR in consecutive cohorts.
Results: 1500 inguinal studies were performed by May 2018. Each cohort of 250 cases confirmed a mean N-VR of 0.4%, 99% CI [0.16-0.5%] and there was no statistically significant difference between any cohort. The false negative studies occurred at random throughout the 15 years observation with a mean specificity rate of 99.1% ranging from 98.5-99.5% across each cohort. In the first cohort the false negative procedures were no. 15, 98 and 201.
Conclusions: This is the largest study reporting long term outcome of the performance of DSNB for SCCp. We have not demonstrated any learning curve and consistent performance of the test over the long term. We have confirmed a benchmark for quality assurance and see no reason to prevent penile cancer units adopting this technique.