DETECTION OF EARLY LYMPH NODE METASTASES IN PROSTATE CANCER BY LAPAROSCOPIC RADIOISOTOPE GUIDED SENTINEL LYMPH NODE DISSECTION

Abstract

Purpose: Radioisotope guided sentinel lymph node (SLN) dissection (SLND) for prostate cancer has been shown to increase the sensitivity of detecting early metastases in open pelvic lymph node dissection. We developed a technique that allows SLND to be performed by laparoscopy in conjunction with laparoscopic radical prostatectomy. Materials and Methods: In 71 consecutive patients SLND was performed by 1 surgeon preceding laparoscopic radical prostatectomy. Mean preoperative prostate specific antigen was 8.88 ng/ml (range 2.1 to 25.4). At 24 hours prior to surgery 3 ml (200 MBq) 99mTc labeled human albumin colloid were injected into the prostate gland under transrectal ultrasound guidance. An especially designed laparoscopic γ probe was used to measure radioactivity during surgery. SLNs were identified and removed. If frozen section analysis showed metastases, extended pelvic lymph node dissection was performed. Results: Radioactivity was detected on 2, 1 and no sides in 50 (70.4%), 19 (26.7%) and 2 patients (2.8%), respectively. In 81 of the 142 pelvic side walls (54.7%) SLNs were exclusively outside of the obturator fossa. Histopathological examination showed metastases to SLNs in 9 patients (12.9%). Eight of the 11 detected metastases (72.7%) were outside of the obturator fossa. Lymph node metastases were exclusively found in 99mTc marked lymph nodes. Mean tumor size was 1.7 mm (range 0.2 to 3.9). Conclusions: SLND is feasible by laparoscopy. It detects micrometastases outside of the obturator fossa in a significant number of patients. We noted that the transperitoneal approach allowing wide exposure and a γ probe with a 90-degree lateral energy window is the most important factor to enable successful laparoscopic SLND.