Lymphoscintigraphy and Sentinel Node Biopsy
Sentinel node biopsy, which has been extensively validated in breast cancer and melanoma, is being used increasingly in the evaluation of penile cancer. The concept of the sentinel node, the first lymph node to contain metastatic cancer within a tumor's lymphatic basin, was introduced by Cabanas in 1977. In an effort to more accurately stage and avoid extensive lymph node dissections in the majority of patients with penile cancer, Cabanas studied 100 cases of local T2 or greater disease using lymphangiograms, anatomic dissections, and/or microscopic evaluations. Anatomically, the sentinel lymph node was discovered to be part of the lymphatic system around the superficial inferior epigastric vein, and theoretically, skip metastases beyond this node were supposedly rare. In the study, 46 sentinel node biopsies were performed, with 15 nodes being positive for metastatic disease and thus warranting a formal inguinal node dissection. No further involvement of other inguinal nodes was present in 12 of these 15 cases. Lymphatic channels draining into the iliac nodes without first draining into the sentinel lymph node were not seen, and inguinal-femoral lymph nodes were not involved with metastatic disease in the absence of sentinel lymph node positive disease. Based on these findings, Cabanas recommended bilateral sentinel node biopsy followed by inguino-femoral dissection only when biopsy of the sentinel node was positive. When the sentinel node was negative for metastatic disease, no further surgical treatment was recommended.
The reliability of this approach was limited by its relatively poor localization technique, and therefore it failed to gain widespread acceptance. Further refinements of the technique, including the use of radiolabeled colloids in conjunction with gamma imaging or gamma probe-guided detection of the sentinel node at surgery, has resurrected the issue. By combining preoperative lymphatic mapping with intraoperative gamma probe detection, use of this nuclear medicine procedure to identify sentinel nodes is increasing.
Horenblas et al reported on a series of 55 patients with stage T2 or greater node-negative disease who underwent lymphoscintigraphy with technetium-99m nanocolloid injected intradermally around the tumor. Sentinel nodes were found intraoperatively using patent blue dye injected intradermally around the tumor and a gamma detection probe (Fig 3). Regional node dissections were limited to patients with tumor-positive sentinel nodes. A total of 108 sentinel nodes were removed, and 11 patients underwent a regional node dissection secondary to a sentinel node positive for metastatic disease. At a median follow-up of 22 months, 1 patient had nodal metastasis despite prior excision of a tumor-free sentinel node. More recently, Valdes Olmos and colleagues reported on a series of 74 patients with T2 or greater disease clinically negative lymph nodes who underwent gamma mapping. The sentinel node visualization rate was 97%, and lymphatic inguinal drainage was bilateral in 81% of cases. Bilateral lymph node drainage was asynchronous in 62%, with half initially draining to the left inguinal nodes and half to the right. In total, 173 sentinel nodes were visualized, with 161 removed at surgery. Twenty-two percent of patients had positive sentinel nodes and underwent a standard regional node dissection. Mean follow-up was 28 months. Two patients with negative sentinel nodes on initial evaluation developed nodal metastasis in the mapped lymphatic basin at follow-up. Both studies concluded that lymphoscintigraphy offers a valid, well-tolerated method for lymphatic mapping and sentinel node identification. However, further study in prospective clinical trials is needed before this technique can be accepted as standard practice.
Images of the sentinel node biopsy demonstrating (A) injection of dye and radiopharmaceutical around primary lesion, (B) localization of the node using the gamma probe, (C) small groin incision to access the sentinel node, and (D) excision of sentinel node.
Cancer Control. 2002;9(4) © 2002 H. Lee Moffitt Cancer Center and Research Institute, Inc.
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Cite this: Cancer of the Penis - Medscape - Jul 01, 2002.