Radioisotope guided pelvic lymph node dissection for prostate cancer

Purpose: The localization of lymph node metastases in prostate cancer varie s enormously. Due to high morbidity complete pelvic lymphadenectomy is ofte n decreased to modified staging lymphadenectomy, resulting in loss of sensi tivity for detecting micrometastases. Based on the promising results of int raoperative gamma probe application for identifying sentinel lymph nodes in malignant melanoma, breast and penis cancer, we identified sentinel lymph nodes in prostate cancer using a comparable technique. Materials and Methods: In 117 patients (99m)technetium nanocolloid was tran srectally injected directly into the prostate under ultrasound guidance 1 d ay before pelvic lymphadenectomy. Thereafter dynamic lymphoscintigraphy was done. Initially lymph nodes identified as sentinel lymph nodes by the gamm a probe were removed and subsequently modified pelvic lymphadenectomy was p erformed. Results: Lymphatic metastasis was detected in 28 cases. An average of 4 sen tinel lymph nodes were identified per patient in 25 of 27 patients with mic rometastasis, of which those in 24 contained micrometastasis for 96% sensit ivity. In contrast, sensitivity of modified pelvic lymphadenectomy was 81.5 %. In 16 patients only sentinel lymph nodes were positive. An average of 21 .8 lymph nodes (range 10 to 51) was dissected per patient at pelvic lymphad enectomy. Lymph node metastasis was noted in 6 of the 46 patients with a pr ostate specific antigen between 4 and 10 ng./ml. and in 8 of the 64 with a stage pT2 tumor. Conclusions: Our study shows individual variability of lymphatic drainage o f the prostate and limited sensitivity for detecting positive lymph nodes w hen the pelvic dissection area is limited. Furthermore, our experience impl ies that the identification of sentinel lymph nodes is feasible, not only i n breast cancer and malignant melanoma, but also in prostate cancer using a comparable technique.