Near infrared imaging to identify sentinel lymph nodes in invasive urinary bladder cancer

Abstract

Approximately 12,000 people are diagnosed with invasive transitional cell carcinoma of the urinary bladder (InvTCC) each year in the United States. Surgical removal of the bladder (cystectomy) and regional lymph node dissection are considered frontline therapy. Cystectomy causes extensive acute morbidity, and 50% of patients with InvTCC have occult metastases at the time of diagnosis. Better staging procedures for InvTCC are greatly needed. This study was performed to evaluate an intra-operative near infrared fluorescence imaging (NIRF) system (Frangioni laboratory) for identifying sentinel lymph nodes draining InvTCC. NIRF imaging was used to map lymph node drainage from specific quadrants of the urinary bladder in normal dogs and pigs, and to map lymph node drainage from naturally-occurring InvTCC in pet dogs where the disease closely mimics the human condition. Briefly, during surgery NIR fluorophores (human serum albumen-fluorophore complex, or quantum dots) were injected directly into the bladder wall, and fluorescence observed in lymphatics and regional nodes. Conditions studied to optimize the procedure including: type of fluorophore, depth of injection, volume of fluorophore injected, and degree of bladder distention at the time of injection. Optimal imaging occurred with very superficial injection of the fluorophore in the serosal surface of the moderately distended bladder. Considerable variability was noted from dog to dog in the pattern of lymph node drainage. NIR fluorescence was noted in lymph nodes with metastases in dogs with InvTCC. In conclusion, intra-operative NIRF imaging is a promising approach to improve sentinel lymph node mapping in invasive urinary bladder cancer.