Sentinel lymph node biopsy in bladder cancer: Systematic review and technology update

A sentinel lymph node (SLN) is the first lymph node to drain a solid tumor and likely the first place metastasis will travel. SLN biopsy has been well established as a staging tool for melanoma and breast cancer to guide lymph node dissection (LND); its utility in bladder cancer is debated. We performed a systematic search of PubMed for both human and animal studies that looked at SLN detection in cases of urothelial carcinoma of the bladder. We identified a total of nine studies that assessed a variety of imaging techniques to identify SLNs in patients with urothelial carcinoma of the bladder. Eight studies investigated human patients while one looked at animal (dog) models. Seven studies representing 156 patients noted the negative predictive value of the SLN to predict a metastasis free state was 92% (92/100). The SLN biopsy was less accurate in metastatic patients with a positive predictive value of only 77% (43/56) with a false negative range of in individual studies of 0-19%. Clinically, positive nodes routinely do not take up the pharmaceutical agent for SLN. Therefore, SLN biopsy is a promising concept with a 92% negative predictive value; however, the false negative rates are high which may be improved by standardizing populations and indications. Novel technologies are improving the detection of SLN and may provide the surgeon with an improved ability to detect micrometastasis, guide surgery, and reduce patient morbidity.