Sentinel Lymph Node Biopsy for Melanoma
by Craig L. Slingluff, Jr., M.D.
Professor, Vice Chair for Research
Department of Surgery
The rationale for sentinel lymph node biopsy in melanoma patients is that the lymphatic drainage for the skin site of a primary cutaneous melanoma can be mapped routinely using standard lymphoscintigraphy techniques which have been time tested over the past several decades. The standard approach for this has been intradermal injection of Technetium-99 labeled sulfur colloid. Standard gamma camera imaging after such injection permits identification of the draining nodal basin or basins usually within a matter of minutes. This procedure was used extensively a decade or two ago. More recently it has been shown that within the nodal basin or basins identified by lymphoscintigraphy, one or two lymph nodes typically can be identified on the lymphoscintigram as the first sentinel node(s) draining the tumor site. With the development of hand-held gamma probes which are small enough to be used in the Operating Room, it is now possible to identify and to resect the sentinel node(s) using the Technician Label as a guide. Injection of vital blue dye (Isosulfan blue) intradermally can facilitate this node identification.
The procedure that we employ for sentinel lymph node biopsy involves the injection of unfiltered Tc-99 sulfur colloid with or without Isosulfan blue intradermally at multiple sites around the melanoma itself or around the biopsy scar. It is preferable that this be done before a wide excision is performed, but occasionally we have performed it after wide excision , generally with good results. Before doing the injection we apply an ointment to the skin which provides some local anesthesia to make the injection less painful. Once the injection is performed, the patient is placed on an imaging table for evaluation with the gamma camera. This is done in the Nuclear Medicine suite. At that time we correlate findings from the gamma camera with those found with the hand-held gamma probe. Once we have evaluated the nodal drainage, the patient is taken to the Operating Room where the location of sentinel node(s) is further confirmed and determined using the hand-held probe. A small incision is made over the identified “hot spot.” The incision usually is limited to about 2-3 cm. We can perform this under local anesthesia although some patients prefer a general anesthetic. The sentinel node(s) is identified and resected and sent for a standard histologic evaluation. Most of these patients have not had a wide excision prior to this procedure, which is the preferred situation. Thus after doing the sentinel node biopsy, a wide excision is performed in the standard fashion.
This is an out-patient procedure and the morbidity is quite small, as would be expected.
Results of Sentinel Lymph Node Biopsy for Melanoma
The reported experience with sentinel node biopsy approaches for melanoma has been that the sentinel node can be identified successfully in well over 90% of cases. Our experience has been that the sentinel node or nodes can be identified successfully in virtually all cases. The ability of the sentinel node or nodes can be identified successfully in virtually all cases. The ability of the sentinel node to predict the findings in the remainder of the nodal basin is very good. Obviously, if that sentinel node is positive for metastatic disease, then that basin is positive. In general, however, detectable metastases are absent from the remaining nodes in that basin. We would expect that those with a positive sentinel node would later develop nodal metastasis in some of the nodes in that remaining nodal basin if they were left in place; so we routinely recommend complete node dissection in the setting of a positive sentinel node.
When the sentinel node is negative it has about 98-99% negative predictive value that the entire nodal basis is negative. Patients who have been followed for several years after a negative sentinel node biopsy do have risk of recurrence in that nodal basin that is in the range of 3-4%. This is based on data from Don Morton’s group in Los Angeles as well as M.D. Anderson and the University of South Florida. These numbers are actually quite similar to the likelihood of recurrence in a node basin after a standard elective lymph node dissection with negative nodes, as we reported in 1994 (Ann. Surg. 219: 120-130).
I consider the indication for a sentinel lymph node biopsy for melanoma to be a patient with clinically negative nodes and a primary melanoma 1 mm thick or greater. The reason for performing the node biopsy is to provide accurate staging. The benefits from this include the opportunity for patients to consider adjuvant therapy if nodes are positive. This is particularly relevant in the setting of alfa- interferon being approved for clinical use, where the only group of patients that seemed to benefit from the interferon were those with positive nodes. There also are some experimental immune therapy protocols including one which we have available at this institution, which requires that the patient either have a thick melanoma or positive nodes. For patients who are not candidates for adjuvant therapy, either due to their own personal preference or to concurrent medical contraindications, I do not routinely recommend sentinel node biopsy. These decisions, however are affected by individual issues for each patient. We are happy to evaluate any patient for consideration of sentinel lymph node biopsy, and we perform it routinely. Any questions related to this procedure should be referred either to me through my secretary Ann Lee (804-924-1730) or through Kathleen Haden, A.N.P. (804-924-1730). I will also be happy to entertain or to respond to any questions by e-mail, email@example.com
Craig L. Slingluff, Jr., M.D.
Professor, Vice Chair for Research
Department of Surgery
PO Box 10005
Charlottesville, VA 22906-0005