Sentinel Node Identification with Hybrid Tracer-guided and Conventional Dynamic Sentinel Node Biopsy in Penile Cancer: A Prospective Study in 130 Patients from the Two National Referral Centres in Sweden

BACKGROUND: Studies suggest that a hybrid indocyanine green (ICG)-99mTc-nanocolloid tracer improves sentinel node (SN) identification compared to conventional dynamic sentinel node biopsy (DSNB). OBJECTIVE: To investigate hybrid tracer-guided SN identification in a multicentre setting and determine false-negative (FN) and complication rates. DESIGN, SETTING, AND PARTICIPANTS: A total of 130 patients with penile cancer scheduled for DSNB were prospectively included between February 2016 and December 2017 at two national Swedish referral centres. ICG-99mTc-nanocolloid hybrid tracer was used in the standard DSNB protocol. INTERVENTION: SNs were identified intraoperatively using radioguidance, fluorescence imaging, and blue dye. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The number of SNs identified by each tracer and the rates of complications and nodal recurrence during median follow-up of 34 mo were recorded. Differences in proportions between groups were compared using χ2 and McNemar's tests. RESULTS AND LIMITATIONS: Overall, 453 SNs were identified preoperatively via single-photon emission computed tomography/computed tomography. Among the 425 SNs excised, radioguidance, fluorescence, and blue dye identified 414 (97%), 363 (85%), and 349 (82%), respectively. Fluorescence imaging helped to detect six SNs that were negative using the other tracers, two of which were from the same patient and contained metastases. Histopathological examination detected 33 metastatic SNs in 20/130 patients (15%). The FN rate was 12% per groin (95% confidence interval 8-16%). CONCLUSIONS: Identification of SNs in patients with penile cancer relies mainly on radioguidance, while fluorescence (ICG) and blue dye methods for optical SN identification are comparable. However, the value of fluorescence imaging should be further evaluated in studies with long-term follow-up. PATIENT SUMMARY: In this study, we investigated addition of a dye called indocyanine green (ICG) for assessment of lymph nodes in patients with cancer of the penis. ICG did not improve the rate of detection of nodes most likely to harbour cancer because of their location in the drainage pathway for lymphatic fluid, but did help in identifying additional metastases.