Introduction

The exact anatomical location of the sentinel lymph nodes (SLNs) for prostate cancer has not ascertained clinically, but could be useful both for diagnosing lymph node metastasis and simplifying the procedure of extended pelvic lymph node dissection (ePLND). The aim of this study was to evaluate the suitability of SLNs detection by intraoperative fluorescence imaging with indocyanine green (ICG) during laparoscopic radical prostatectomy (LRP) and to determine the position of the SLNs.

Methods

A consecutive series of 50 patients with intermediate and high risk localized prostate cancer who underwent LRP between January 2014 and September 2016 was analyzed. ICG was injected into the prostate via transrectal ultrasound guidance 30 minutes before surgery. Intraoperative fluorescence imaging was performed using the Olympus near-infrared camera system. LRP was performed, starting with SLNs dissection and ePLND followed by prostatectomy.

Results

Median patient age was 70 years (range 61-76) and median PSA was 8.9 ng/ml (range 5.0-62.1). In addition, 24 cases (48%) were intermediate risk, 26 (52%) were high risk .SLNs were identified in 47 patients (94%). Two hundred ninety-four SLNs were removed (median 5 SLNs per patient, range 0-16), and overall 1013 nodes (median 16 nodes per patient, range 6-33) were removed during ePLND. The incidences of lymph node metastasis were 12% (6/50). Although the false negative rate was 0% and the sensitivity was 100% on a per-patient basis, pathological examination revealed a total of 22 metastatic nodes, of which 63% (14/22) were ICG stained. Importantly, 11 positive nodes which were all ICG stained were located below the bifurcation of the common iliac arteries in 5 of the 6 patients. Approximately 90 % of these positive SLNs (10/11) were located at two predominant sites along the characteristic lymphatic pathways. One was the junctional lymph nodes (45.5%, 5/11) which were located at the junction between internal and external iliac vessels, and the other was the distal internal iliac lymph nodes (45.5%, 5/11) which were located along the inferior vesical artery.

Conclusions

Intraoperative fluorescence imaging with ICG is feasible for detecting SLNs for prostate cancer. Our anatomical evaluation indicated that most of the positive SLNs are located at the junctional or the distal internal iliac lymph nodes. Although further investigation is needed, the possibility of ePLND overlook lymph node metastasis may be overcome by identifying these SLNs.

Funding

none