Diagnostic Value of Radio-Guided Sentinel Node Detection in Patients with Prostate Cancer Undergoing Radical Prostatectomy with Modified-Extended Lymphadenectomy

SIMPLE SUMMARY: Radio-guided sentinel lymph node (SLN) detection techniques are utilized in many malignancies, including breast and penile cancer. In the setting of prostate cancer (PCa), SLNs identification had low specificity and sensitivity in available studies, and extended pelvic lymph node dissection (ePLND) remains the gold standard in the assessment of nodal invasion. Our study is the first to detect SLNs pre- and intraoperatively while performing ‘whole-pelvis’ modified-extended lymphadenectomy (mePLND), including lymph nodes (LNs) from the ePLND template, as well as the presacral and Marcille’s fossa areas. The aim of this study was to assess the efficacy of single-photon emission computed tomography (SPECT-CT) and the gamma-probe in the SLN detection, as well as to map lymphatic drainage patterns in the prostate. Results showed that the SLN detection technique has very low specificity and relatively high sensitivity and remains a poor nodal staging tool in intermediate- and high-risk PCa patients. ABSTRACT: Background. In many malignancies, sentinel lymph node dissection (SLND) is being used as a nodal staging tool. We prospectively evaluated the diagnostic value of radio-guided sentinel lymph node (SLN) detection in patients with prostate cancer (PCa). This study aimed to investigate the reliability of the radio-guided SLN detection technique for perioperative localization of LNs metastases as well as to map lymphatic drainage patterns of the prostate. Methods. Forty-three patients with intermediate- or high-risk cN0cM0 PCa at conventional imaging underwent radical prostatectomy with modified-extended pelvic lymph node dissection (mePLND). A day before the planned surgery, a Tc-99m nanocolloid was injected into the prostate under the control of transrectal ultrasonography (TRUS). Preoperative single-photon emission computed tomography (SPECT-CT) imaging and intraoperative gamma-probe were used to identify SLNs. All positive lesions were excised, followed by mePLND. The excised lymph nodes (LNs) were then submitted for histopathological examination, which was used as a reference for the calculation of diagnostic parameters of the SLN technique for SPECT-CT and the intraoperative gamma-probe. Results. In total, 119 SLNs were detected preoperatively (SPECT-CT) and 118 intraoperatively (gamma-probe). The study revealed that both SLN detection techniques showed a sensitivity of 90% and a specificity of 6.06%. The negative predictive value (NPV) was 66.67%. SLN technique would have correctly staged nine of 10 patients, which is the same result as in the case of limited LND. However, it allowed the removal of all metastatic nodes only in four of them. SLND would have comprised 69.7% of preoperatively detected LNs, and removed 13 out of 19 positive LNs (68.42%), respectively. Conclusions. Radio-guided SLND has a low diagnostic rate and is a poor staging tool. ePLND remains the gold standard in nodal metastases assessment in PCa. Our study indicates that lymphatic drainage of the prostate and actual metastasis routes may vary significantly.