Sentinel lymph node biopsy for squamous cell carcinoma of the anal canal

Abstract

Background: The current Trans-Tasman Radiation Oncology Group (TROG) protocol for T1 and T2 anal cancers is combination chemotherapy and radiotherapy excluding the inguinal region from the field. Several centres worldwide irradiate both inguinal regions as there is a small incidence of involvement with early stage tumours. The presence of inguinal lymph node metastases is not accurately detected using clinical and most radiological assessment modalities. We have developed a method of sampling the sentinel node in the groin using established node mapping techniques. Methods: A combination of radio-labelled Antimony Sulphide and Patent Blue dye injected around the anal cancer enable identification of the sentinel node in the groin, using a gamma probe and direct visualization of the blue node. Results: This technique has been used in four patients. A groin sentinel node was identified and removed in three of these, with pathological assessment excluding metastatic disease in the inguinal region. The fourth patient had a sentinel node mapped to a meso-rectal node. This was not sampled. Conclusions: The application of this effective technique will allow accurate staging of anal cancers to better plan future treatment regimes.