Point counterpoint: Sentinel lymph node mapping controversy

Key Points

Controversy swirls around the value of sentinel lymph node biopsy (SLNB) for melanoma patients. Dermatology Times sought the input of two experts, Arthur J. Sober, M.D., dermatologist and professor of dermatology, Harvard Medical School, Boston, and John Zitelli, M.D., dermatologist, associate clinical professor, University of Pittsburgh, Pittsburgh, to discuss both sides of the SLNB issue. Dr. Sober weighs in on the pro side, and Dr. Zitelli is against routine sentinel lymph node biopsy.

DT: Is there a survival benefit to performing sentinel node biopsies?

Dr. Sober: There is data that suggests that there may be a survival benefit, and that comes from the recent paper of Dr. D. Morton's (N Engl J Med. 2006 Sep 28; 355(13):1307-1317) showing a difference in survival at five years between patients that had positive sentinel nodes and patients who subsequently developed clinically positive nodes who had not been recipients of sentinel node biopsies.

DT: Who would be a candidate for sentinel node biopsy?

Dr. Sober: That differs from center to center. But most surgeons who believe in the value of sentinel node biopsy will offer it to people who have primary melanomas greater than a millimeter. And some centers will select patients less than a millimeter if a shave biopsy was done and the true thickness could not be determined, or if they have other risk factors, such as a the presence of an ulcer or Clark's level 4 or 5.

Dr. Zitelli: Sentinel node biopsy has a place in research - for stratifying patients in a clinical trial. And you might get a slight amount of prognostic information in patients whose melanomas are 2 mm to 4 mm thick.

(Dr. Zitelli disagrees with the way Dr. Morton et al interpreted the Sept. 28, 2006, study in the New England Journal of Medicine.) The authors (of the New England Journal of Medicine study) would like you to believe that the sentinel lymph node procedure is the most important prognostic indicator for patients with melanoma. Therefore, even though it does not give you survival benefit, you should do it in anybody who has a melanoma more than a millimeter thick, just so that you can give them a better estimate of the prognosis.

But, the amount of information that you get actually is very limited, because if you look at melanomas by thickness, the prognosis is the same whether the sentinel node is positive or negative in melanomas that are less than a millimeter thick. If your melanoma is 1 mm to 2 mm thick, there is very little difference in prognosis, whether your sentinel lymph node is positive or negative. In that case, sentinel lymph node biopsy is probably not worth the risk of the procedure. If your melanoma is more than 4 mm thick, the prognosis is pretty much the same whether your sentinel lymph node is positive or negative. The only place sentinel lymph node biopsy made a difference was in the 2 mm to 4 mm thick group. In that group, patients whose lymph nodes were positive had a five-year survival rate of 40 percent versus 76 percent if their sentinel lymph nodes were negative.

So, there is a difference there, but it does not tell that patient absolutely whether they will live or die and if sentinel lymph node biopsy is worthwhile.

The other problem is when sentinel node biopsy is done for prognosis and a positive lymph node is found, doctors often automatically put patients on this bandwagon of additional therapy that has not been shown to be of any benefit.

DT: Are there benefits of doing sentinel node biopsy as a staging procedure?

Dr. Sober: That is probably the more substantiated benefit - allowing the early determination of patients that have micrometastatic disease.