1403 DOES THE LYMPHATIC DRAINAGE PATTERN OF THE LATERAL BLADDER WALL MAKE A BILATERAL PELVIC LYMPHADENECTOMY (PLND) UNNECESSARY IN STRICTLY LATERALLY LOCALIZED INVASIVE BLADDER CANCER? RESULTS OF A MULTIMODALITY MAPPING STUDY

INTRODUCTION AND OBJECTIVES: To use single photon emission computed tomography (SPECT) combined with computed tomography (CT) plus intraoperative gamma probe verification to map the primary lymphatic landing sites of the of the lateral bladder wall. METHODS: Clinical trial of 40 consecutive cystectomy patients with unilateral bladder cancer ( cT3, cN0, cM0) at a single center. One day prior to surgery flexible cystoscopy-guided injection of Tc-99m nanocolloid into the non-tumor-bearing lateral bladder wall (left: n 21; right: n 19) was performed. All patients underwent SPECT-CT 3 and 6 h after injection of the radiopharmaceutical with a bladder flushing catheter in place. The SPECT-CT detected radioactive lymph nodes (LNs) were confirmed intraoperatively with a gamma probe at the time of PLND. Radioactive LNs were removed separately. A backup extended PLND was performed to preclude missed primary lymphatic landing sites. The SPECT-CT and intraoperative findings were used to generate a three-dimensional projection of each LN site. RESULTS: A total of 1655 LNs (median 39 LNs per patient; range 21–83) were resected. 228 of these were radioactive (median 6 radioactive LNs per patient; range: 1–17). 193 radioactive LNs (85%) were located on the ipsilateral side of the injection and 35 (15%) on the contralateral side (external iliac 6%, obturator fossa 5%, common iliac 4%), but none in the internal iliac region. Only 11% of radioactive LNs were located cephalad to the uretero-iliac crossing. All patients had at least 1 radioactive LN on the ipsilateral side. 40% of patients had at least 1 additional radioactive LN on the contralateral side. CONCLUSIONS: A unilateral PLND would have missed radioactive LNs on the contralateral side in 40% of patients. Therefore, a bilateral extended PLND including the common iliac region up to the uretero-iliac crossing is mandatory even in strictly laterally localized bladder tumors. Still, we could not detect any radioactive LNs in the contralateral internal iliac region. Therefore, contralateral PLND may be limited to the obturator fossa, external iliac and common iliac region which has influence on nerve sparing in patients who are candidates for an ileal bladder substitute.