Systematic review of sentinel lymph node biopsy in anal squamous cell carcinoma

Background: Anal squamous cell carcinoma with lymph node metastases carries a poor outcome. There remains a need for a better method to diagnose inguinal lymph node metastases which is minimally invasive, accurate and avoids unnecessary irradiation to the groin with its associated significant co-morbidity. The aim of this study was to evaluate the role of sentinel lymph node (SLN) biopsy in anal squamous cell carcinoma. Methods: The systematic review was conducted in accordance with PRISMA guidelines. The Medline, Central and Embase databases were searched using the terms 'sentinel lymph node' and 'anus neoplasms'. Results: The systematic review identified 17 studies, containing 270 patients. SLN detection rate varied from 47% to 100%. The presence of nodal metastases varied from 0 to 44%. The complication rate varied from 0 to 59%. The rate of development of subsequent inguinal lymph node metastases in those previously SLN biopsy-negative (a surrogate marker for false negative rate) ranged from 0 to 18.75%. Conclusion: SLN biopsy is a feasible method of assessing lymph node status in patients with anal squamous cell carcinoma. Longer follow up is required to evaluate the proportion of patients who are SLN biopsy-negative and subsequently develop nodal metastases. More studies are required to ascertain whether SLN biopsy should be the main method of assessing inguinal lymph node involvement in patients with anal squamous cell carcinoma.