Arguments for a valuable tool: Sentinel lymph node biopsy in malignant melanoma

John M. Kirkwood, M.D., professor and vice chairman for clinical research of the department of medicine at the University of Pittsburgh School of Medicine and director of the melanoma and skin cancer program at the University of Pittsburgh Cancer Institute, tells Dermatology Times, "Sentinel lymph node biopsy is a key prognostic factor for patients with melanoma who have an increasing risk of clinically occult nodal disease as the primary tumor thickness increases. Furthermore, sentinel lymph node biopsy can help physicians identify patients who are potentially suitable for possible adjuvant interferon-(IFN) alpha-2b therapy, and enables inclusion of more uniformly defined patient populations in clinical trials of newer adjuvant therapies."

The multicenter selective lymphadenectomy trial (MSLT-1) was designed to examine the efficacy of SLNB plus immediate complete lymph node dissection (CLND) vs. delayed CLND ("watch and wait" group).

"In the study, progression to more advanced nodal disease occurred at a higher rate in the patients assigned to the 'watch and wait' policy, as compared to patients who had SLNB and treatment according to the findings at SLNB.

"The patients in the 'watch and wait' group have recurrences that are associated with a greater adverse impact upon survival. The data suggests that micrometastases of melanoma, if left untreated, will grow and metastasize over time," Dr. Kirkwood says.

Argument for SLNB

Dr. Kirkwood contends that, while elective lymph node biopsy (ELNB) may be becoming archaic, the great value of SLNB should not be ignored.

"While we have dismissed the older dogma that elective lymph node dissection is the standard of care," he explains, "Sentinel node biopsy is not a modification of this procedure that must be abandoned and referred to only in historical context as a useless technique, but rather that sentinel node biopsy is a scientifically well founded approach that logically builds upon the knowledge about lymphatic metastatic spread. It affords the patient and physician a very low-risk and highly informative prognostic assessment that permits patients to plan their future therapy on the highest level of information, beyond any potential surgical benefits that the procedure may offer."

He notes that a sentinel lymph node biopsy, which is done at the time as wide excision, should be considered the standard treatment. This procedure has a failure rate of under 4 percent in negative basins, and reduces the former broader pursuit of complete lymph node dissection to focus this surgery upon only the patients at higher risk with a positive sentinel lymph node. He adds that regional disease is rare after complete node dissection for positive sentinel nodes.

According to Dr. Kirkwood, there are a few essential arguments in favor of doing a sentinel lymph node biopsy.

Prognosis and staging

SLN status has been demonstrated repeatedly to be the most powerful independent prognostic factor predicting survival.

Dr. Kirkwood says that SLNB permits the modern oncologist to rationally individualize treatment for localized melanoma, and has significant advantages over the former policy of ELND.

He explains that restricting complete node dissections to only those patients with a proven metastasis in the sentinel node reduces the morbidity for the node-negative population of patients and assures better staging for the node-positive patients. The SLNB uniquely allows the identification and assessment of "intercalated" or in-transit nodes that are missed by ELND.

Sentinel node mapping and biopsy has advantages over ELND in terms of the detection of unusual metastatic patterns, and in-transit disease. Preoperative drainage scans demonstrate nodes that are missed with all other approaches.