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Lymphatic mapping and sentinel lymph node biopsy in urinary bladder cancer: A SPECT/CT-based experience
Amin Saber Tanha1, Ramin Sadeghi1, Hamidreza Ghorbani2
1Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
Objective:
Sentinel lymph node (SLN) mapping in bladder cancer has the potential to improve nodal staging while minimizing the morbidity associated with pelvic lymph node dissection (PLND). However, its feasibility, diagnostic accuracy, and influencing factors-including tumor stage, neoadjuvant chemotherapy (NAC), and imaging modality-remain under investigation.
Materials And Methods:
In this prospective study, 35 patients with T1-T4 urothelial carcinoma undergoing radical cystectomy and bilateral PLND were enrolled. Preoperative cystoscopic peritumoral injection of 99mTc-phytate was followed by planar lymphoscintigraphy and SPECT/CT. Intraoperative SLN detection utilized a handheld gamma probe. SLN identification was compared with standard PLND findings using patient- and hemipelvis-based analyses to determine detection rates, sensitivity, and false-negative rates.
Results:
A total of 54 SLNs were identified in 24 patients (37 hemipelves). Patient-based detection rates were 68.6% for intraoperative gamma probe, 51.4% for SPECT/CT, and 45.7% for planar imaging. Hemipelvis-based detection rates were 52.9%, 40.0%, and 34.3%, respectively. Detection rates were highest in T1-T2, NAC-positive patients, with 100% intraoperative localization. Histopathological analysis identified nodal metastases in seven patients; SLNs were identified in four patients, three of whom showed concordant SLN involvement, while one showed no SLN involvement. The patient-based false-negative rate was 25%, while hemipelvis-based analysis showed no false negatives. Aberrant SLNs outside the standard PLND template were identified in 6% of patients, highlighting variable lymphatic drainage.
Conclusion:
SLN mapping in bladder cancer is technically feasible and identifies atypical drainage patterns, with performance influenced by tumor stage, NAC, and imaging modality. SLN mapping may complement PLND by improving anatomical staging and may ultimately allow more tailored or minimally invasive lymphadenectomy in selected patients.
