Standing watch: Sentinel lymph node biopsy demonstrates therapeutic results

Key Points

Toronto - The sentinel lymph node biopsy may not only stage the regional lymph nodes of patients with melanoma and have prognostic value, but may be therapeutic as well, according to an assistant professor at the University of Toronto.

Speaking at a general surgery update organized by the University of Toronto on the management of extremity and trunk melanomas, Frances Wright, M.D., a surgical oncologist at Sunnybrook Health Sciences Centre in Toronto, said data from a randomized trial consisting of patients with clinically node-negative melanoma demonstrated a survival advantage in a subset of patients who had a positive node.

Dr. Wright cites data from the international Multicenter Selective Lymphadenectomy Trial (MSLT-1) that compared two therapeutic approaches in more than 1,300 patients with early-stage melanoma, with most patients having melanomas measuring between 1.2 mm and 3.52 mm in depth.

There was no overall survival difference when comparing patients who underwent a biopsy and those who did not undergo a biopsy, but subset analysis of the data did show a difference.

"When you look at the overall survival, there was a statistically significant difference," Dr. Wright says, referring to a 16 percent overall survival advantage at five years for sentinel lymph node positive patients who underwent complete lymphadenectomy.

Clinical trials have shown that 80 percent of patients who undergo a sentinel lymph node biopsy will be node-negative, and the other 20 percent will be node-positive.

In her own clinical experience, Dr. Wright says the majority of patients do want to undergo the sentinel lymph node biopsy and surgery.

Dr. Wright describes a further melanoma study, MSLT-2, which aims to determine whether melanoma-specific survival associated with intraoperative lymphatic mapping and sentinel lymphadenectomy alone and close clinical and radiologic follow up is equivalent to melanoma-specific survival associated with lymphatic mapping, sentinel lymphadenectomy and complete lymph node dissection, in patients with sentinel node metastases detected by histopathologic or molecular techniques.

Data trend

An interesting trend observed in the data from the MSLT-1 study relates to surgical experience. A surgeon's experience with melanoma cases and with performing a sentinel lymph node biopsy lessens the risk of local recurrence.

The rate of false-negative sentinel node biopsy, as indicated by nodal recurrence in a tumor-negative, dissected sentinel node basin, fell as the case volume rose at each center: 10.3 percent for the first 25 cases vs. 5.2 percent after 25 cases. Dr. Wright notes that the trial involved well-trained surgeons.

"It's clear that you do need to perform a large number of cases to get a lower rate of recurrence," Dr. Wright tells Dermatology Times.

When surgeons perform the sentinel lymph node biopsy, they should ideally be using both blue and technetium dye to yield the greatest accuracy, according to Dr. Wright.

Surgeons need to be cautious of the appearance of a lymphatic lake after-dye injection. The lymphatic lake does not have to be excised, for it clears out on its own.

Lymphoscintigraphy is an absolute must when performing a sentinel lymph node in a melanoma case, Dr. Wright says.

In complex cases of melanoma, such as atypical Spitz nevi, care is optimized when it is multidisciplinary.

"Melanoma is a very pathology-based disease," Dr. Wright says.

Dr. May Lynn Quan, M.D., M.Sc., assistant professor in the department of surgery at the University of Toronto and a surgical oncologist at Sunnybrook Health Sciences Centre, says that, in general, sentinel lymph node biopsy is offered to patients who have a melanoma that has a thickness of greater than 1 mm.

Exceptionally, patients with thinner melanomas that measure more than 0.75 mm, but have other poor prognostic features such as ulceration, may be considered on a case-by-case basis for sentinel lymph node biopsy.

At present, some provincial cancer agencies in Canada are drafting guidelines for clinicians on the use of the sentinel lymph node biopsy in melanoma, Dr. Quan says.

The MSLT-1 trial indicated that in patients who underwent a sentinel lymph node biopsy, the procedure served to identify patients with microscopic disease significantly earlier than those without, she says.

"In addition, the number of nodes that are positive is less if you discover them earlier," Dr. Quan says.