All newly diagnosed melanoma patients with tumors of intermediate thickness – defined as those with a Breslow thickness of between 1 and 4 mm – should undergo sentinel lymph node biopsy, according to a new guideline from two professional societies.
The guideline, issued jointly July 9 by the American Society of Clinical Oncology and the Society of Surgical Oncology, also advises that while the use of sentinel lymph node biopsy (SLNB) in people with thicker or thinner melanomas remains contentious, both categories of patients could benefit from SLNB in some circumstances.
All melanoma patients with a positive SLNB, the guideline says, should be treated with completion lymph node dissection (CLND), the current standard of care, although, the authors noted, it is not yet known whether CLND after a positive SLN biopsy improves 10-year overall survival. This is the subject of a large, ongoing randomized trial, the Multicenter Selective Lymphadenectomy Trial II (MSLT-11).
The guideline’s authors, led by Dr. Sandra L. Wong of the University of Michigan, Ann Arbor, and Dr. Gary H. Lyman of Duke University, Durham, N.C., aimed to use the most current evidence to clarify both the indications for sentinel node biopsy and the role of completion biopsy in people with melanomas.
"It is critically important to identify those patients for whom the expected benefits of resecting regional lymph nodes outweigh the risks of surgical morbidity," they wrote in their analysis.
To this end, Dr. Wong, Dr. Lyman, and 12 other expert panel members undertook a broad literature search and identified 73 studies (most of them observational in design) that met the criteria for inclusion in their meta-analysis. Some 25,000 patients were enrolled in the included studies.
The authors found that while robust evidence supports routine use of sentinel lymph node biopsy (SLNB) in intermediate melanomas, there is also some evidence to support the procedure in patients with thin melanomas (less than 1 mm) when certain other risk factors are present, and in patients with thick melanomas (greater than 4 mm).
For people with melanomas of less than 1 mm Breslow thickness and one or more risk factors such as tumor ulceration or a mitotic rate of 1/mm2 or greater, they wrote, "the benefits of pathologic staging may outweigh the potential risks of the procedure," particularly in the subgroup of patients with melanomas ranging from 0.75 mm to 0.99 mm.
Patients with melanomas of 4 mm or greater may also benefit, the guideline says. "Conventional wisdom asserts that patients with thick melanomas have a high risk of systemic disease at the time of diagnosis and that no survival benefit can be derived from removal of regional lymph nodes," the authors wrote.
"However, among patients without distant disease, it can be argued that those with thick melanomas have indications for SLN biopsy similar to those of patients with intermediate-thickness melanomas and derive the same benefits from SLN biopsy as a pathologic staging procedure. One of the main advantages of SLN biopsy in patients with thick melanomas is better regional disease control."
The guideline reiterates that CLND should remain the standard of care for patients with tumor-positive SLNs, even absent survival data from the ongoing MSLT-II trial. The authors cited in support of this evidence from studies that saw nodal recurrence after CLND of between 4.2% and 4.9%. By contrast, as Dr. Wong and colleagues reported in an earlier study, patients in whom CLND was not performed saw a 15% rate of regional nodal recurrence as a site of first metastasis and 41% overall regional nodal recurrence rate (Ann Surg Oncol 2006 13:302-309).
"Until final results of MSLT-II are available, we will not be able to determine, with higher-level evidence, the impact of CLND on regional disease control. Until that time, the best available evidence suggests that CLND is effective at achieving regional disease control in the majority of patients with positive SLNs," the authors wrote.
The guideline was commissioned by ASCO and SSO. The authors disclosed no conflicts of interest.