Methods of Sentinel Lymph Node Detection and Management in Urinary Bladder Cancer—A Narrative Review

Abstract

Introduction: Detection of lymph node status in bladder cancer significantly impacts clinical decisions regarding its management. There is a wide range of detection modalities for this task, including lymphoscintigraphy, computed tomography, magnetic resonance imaging, single-photon emission computed tomography, positron emission tomography, and fluoroscopy. We aimed to study the pre- and intraoperative detection modalities of sentinel lymph nodes in urinary bladder cancer. Method: This narrative review was performed by searching the PubMed and EMBASE libraries using the following search terms: (“Transitional cell carcinoma of the bladder” OR “urothelial cancer” OR “urinary bladder cancer” OR “bladder cancer”) AND ((“sentinel lymph node”) OR (“lymphatic mapping”) OR (“lymphoscintigraphy”) OR (“lymphangiography”) OR (“lymph node metastases”)). Studies analysing the effectiveness and outcomes of sentinel lymph node detection in bladder cancer were included, while non-English language, duplicates, and non-article studies were excluded. After analysing the libraries and a further manual search of bibliographies, 31 studies were included in this paper. We followed the RAMESES publication standard for narrative reviews to produce this paper. Results: Of the 31 studies included, 7 studies included multiple detection methods; 5 studies included lymphoscintigraphy; 5 studies included computed tomography and/or single-photon emission computed tomography; 5 studies included fluoroscopy; 4 studies included magnetic resonance imaging; and 5 studies included positron emission tomography. Discussion: Anatomical, radioactive, and functional detection modalities have been studied independently and in combination. The consensus is that preoperative detection with imaging helps guide surgical management and intraoperative detection methods help capture any lymph nodes that may have been missed. Each of these types of detection represent their own set of benefits and drawbacks, but there is currently limited evidence to support any change in overall practice to replace conventional staging.

The Role of Lymph Node Dissection in the Management of Upper Urothelial Cancer: A Nodal Status-Based Meta-Analytical Study

“…There are various methods to detect and manage sentinel LNs. 43 These include molecular lymphatic mapping, which has shown promise in accurately identifying sentinel LNs with the disease through a focused histopathological evaluation of the suspected nodes and, therefore, has resulted in improvements in the diagnosis of even micrometastases. 44 Another method is PET scanning which provides functional rather than structural visualization of suspected LNs.…”

“…Unlike conventional computed tomography and magnetic resonance imaging, PET is able to successfully identify the occurrence of metastasis even in normal-sized LN with high diagnostic accuracy (sensitivity = 92%, specificity = 91%). 43 Additionally, molecular LN analysis could alter the diagnostic process for sentinel LNs. Its efficacy lies in its ability to detect cancer-enhanced transcripts with very high sensitivity for detecting LN metastasis in solid tumors.…”

Sentinel Lymph Node Techniques in Urologic Oncology: Current Knowledge and Application

“…SLNB for bladder cancer (BCa) is a promising technique, but its application is limited due to the anatomical complexities of the bladder's bilateral lymphatic drainage system and intricate mechanism of lymphatic metastasis [112]. The primary lymphatic drainage from the bladder flows toward multiple groups of LNs in the pelvis, serving as intermediate stations, and it may extend beyond the perivesical region, resulting in challenges for the SLNB technique.…”

Diagnostic Value of the Sentinel Lymph Node Technique in Patients with Muscle-Invasive Bladder Cancer

“…Overall, patients may be diagnosed with one of the two main histopathological stages: non-muscle invasive bladder cancer (NMIBC, stage pTa or pT1), which represents approximately 70% of cases, and tumour-invading detrusor muscle (muscle-invasive bladder cancer MIBC; stage T2-T4), constituting the remaining 30% of cases. Despite an optimal treatment and no histopathological findings of lymph node (LN) metastases, MIBC is associated with a 50% mortality rate over 5 years [4]. This indicates that half of patients diagnosed with MIBC have cancer metastases that are not detected by currently used staging techniques.…”