Sentinel node biopsy in penile cancer: a national retrospective study from Denmark

INTRODUCTION & OBJECTIVES: Nodal involvement is a strong prognosticator in penile cancer and lymph node staging is crucial. Sentinel node biopsy (SNB) has proven a useful staging tool with few complications, but evidence rely mostly on single institution publications with a short follow-up. In this study we estimated the diagnostic accuracy of SNB in patients with squamous cell carcinoma of the penis and assessed procedure-related complications in a multicentre setting with long-term follow-up. MATERIAL & METHODS: Data was retrospectively collected from medical records by one medical doctor at the four university centres where the procedure was performed. Thus, the study covers all SNB procedures performed in Denmark in the 11-year period 2000-2010. Included patients were newly diagnosed and had either non-palpable lymph nodes (cN0) in one or both groins or had a palpable mass in the groin, from which aspiration cytology was unable to detect malignancy. Routine ultrasound of cN0 groins was not used. Patients were injected with nanocolloid technetium and a scintigram was recorded before the surgical SNB. A gamma probe and intraoperative palpation of the exposed inguinal wound was used for the detection of lymph nodes. In addition 1 ml of Patent blue was used intradermally in the circumference of the proximal penile shaft just prior to surgery in 3 centres. Diagnostic accuracy was calculated on the basis of histopathology and complete follow-up until October 2014. RESULTS: 409 groins in 222 patients were examined by SNB. Median follow-up of patients who survived was 6.6 years (interquartile range: 5-10). No patient was lost to follow-up. A total of 1004 lymph nodes were removed of which 93 nodes (9.3 %) harboured metastatic tissue at histopathological examination. All groins with positive SNB underwent complementary ipsilateral ILND. Sixteen groins (24 %) contained further positive lymph nodes, while 50 groins (76 %) had no further metastases on histopathological examination of ILND specimen. In total 66 groins (52 patients) had positive SNB and 343 groins had negative SNB. During a median follow-up of 73 (IQR 53- 102) months 8 false negative groins were encountered. Sensitivity was 89.2% (95% CI, 79.8-95.2%) per groin and false negative rate was 10.8% (95% CI, 4.8-20.2%). Remarkably, four of 67 T1G1 patients had a positive SNB. This is interesting considering the current EAU recommendation with no surgical staging of T1G1 tumours. Twenty-eight of 222 (13%) patients experienced 39 postoperative complications of Clavien-Dindo grade I-IIIa to SNB during follow-up. Complications were encountered after 30 of 409 (7%) procedures and were primarily grade I. One patient was readmitted because of severe wound infection, the remaining complications were handled as a part of primary hospitalization, or in the outpatient clinic. 8 patients experienced more than one SNB-related complication. No patient needed to return to the operating room because of SNB related complications. No patient died from complications. CONCLUSIONS: To our knowledge, this is the first complete national study on sentinel node biopsy. Penile cancer sentinel node biopsy with a close follow-up is a reliable lymph node staging and has few complications in a national multicentre setting. Inguinal lymph node dissection which has complication rates of 30 - 70 % was avoided in 76 % of patients. The EAU guideline recommendation with no surgical staging of T1G1 tumours should be reconsidered.