[Feasibility and value of the isotope sentinel node mapping technique in prostate cancer].

Objective: Use of an isotope sentinel node mapping technique in prostate cancer to study its feasibility, lymphatic prostate drainage and its value in pelvic lymph node staging.
Material and Method: The sentinel node mapping technique was performed in 34 patients with clinically localized prostate cancer. A transrectal intraprostatic injection of Technetium 99m-labelled nanocolloidal particles was performed on the day before radical prostatectomy. Sentinel node mapping was performed by intraoperative lymphoscintigraphy and gamma probe. A standard pelvic lymphadenectomy was systematically performed.
Results: Preoperative lymphoscintigraphy allowed identification of sentinel nodes in 85.3% of patients. Four of the five failures had a history of pelvic surgery. Sentinel node mapping and biopsy were possible in 23 patients (67.7%). The majority of sentinel nodes were located in the hypogastric region (58.4%). A microscopic lymph node metastasis was identified in 4 patients (11.7%), located in a sentinel node in 3 cases. In 2 cases, the micrometastasis was situated in a sentinel node outside of the pelvic chain. These four patients had a pretreatment PSA > 10 ng/ml and a Gleason score > or = 7 (on the prostatectomy specimen).
Conclusion: This study confirms the feasibility of the sentinel node technique in prostate cancer and the diversity of lymphatic drainage of the prostate. Pelvic lymphadenectomy alone also appears to be insufficient for precise staging in patients with pretreatment PSA > 10 ng/ml and a Gleason score > 6. This isotope technique could therefore improve the yield of lymphadenectomy by limiting its extent.