Sentinel lymph node biopsy controversy continues

July 1, 2012

Although sentinel lymph node biopsy (SLNB) may be useful for staging of intermediate-thickness melanomas, says Pamela Basuk, M.D., its utility elsewhere is questionable.

Key Points

Las Vegas - Although sentinel lymph node biopsy (SLNB) may be useful for staging of intermediate-thickness melanomas, says Pamela Basuk, M.D., its utility elsewhere is questionable.

Dr. Basuk spoke at the 2011 Cosmetic Surgery Forum. She is a dermatologist in private practice in Bay Shore, N.Y.

Data regarding the role of SLNB in melanoma treatment remain controversial, Dr. Basuk says. On one hand, SLNB is one criterion in melanoma staging for treatment planning. It may be useful for melanomas of intermediate thickness, she says, and SLNB results are used to enter patients into a clinical trial.

As for melanomas measuring at least 4 mm thick, Dr. Basuk says that in a 121-patient study, 31 percent of SLNB-negative patients died within five years, versus 32.5 percent of SLNB-positive patients (Essner R, Chung MH, Bleicher R, et al. Ann Surg Oncol. 2002;9(8):754-761).

Current data show that performing SLNB confers no increases in overall survival, regardless of SLNB results, Dr. Basuk says. "Additionally, 10 percent to 15 percent of patients who have negative SLNB will go on to develop metastatic disease. And one-third of patients who do have a positive lymph node will not develop metastatic disease. In some studies, micrometastatic SLNB-positive patients have the same long-term survival as SLNB-negative patients."

Furthermore, "Only 20 percent of patients who have a positive lymph node will have other positive nodes after complete lymphadenectomy," she says. "This means that 80 percent of patients are having elective lymph node dissection (ELND) with no benefit. It's not known whether microscopic disease on biopsy equals macroscopic disease. And patients with melanoma die of distant disease. There's no evidence that removing a positive lymph node will change survival."

Before 1990, "ELND was used to stage regional lymph nodes for patients with melanoma at Breslow depths measuring 0.75 to 4 mm." However, Dr. Basuk says, ELND is no longer performed because no trial ever showed that it increased survival.

In this regard, she says the 1,269-patient Multicenter Selective Lymphadenectomy Trial (MSLT-I), which compared outcomes of patients who underwent ELND (after a positive SLNB) versus those who were closely monitored for clinical signs of progression, has proven very controversial.

Ultimately, the study investigators found no increased five-year survival in patients who had positive or negative lymph nodes, and survival for the SLNB group was 78.3 percent, versus 1 percent in an observation group who underwent ELND only if clinically palpable nodes developed during the 60-month follow-up period (Morton DL, Thompson JF, Cochran AJ, et al. N Engl J Med. 2006;355(l3):1307-1317. Erratum in: N Engl J Med. 2006;355(18):1944).

According to Dr. Basuk, however, this study had faults, most notably the fact that investigators included patients in the SLNB-positive column when micrometastases were the only positive indication.

"Patients with micrometastases were included in the SLNB-positive group," she says, "but they are known to have a better prognosis than other SLNB-positive patients."

To clarify the role of micrometastases, Dr. Basuk says, a follow-up study called the MSLT-II is now recruiting patients. Its goal is to determine whether SLNB followed by ELND is superior to SLNB plus ultrasonography in patients with micrometastatic disease in their lymph nodes.

"Another major problem with ELND is inaccuracy in the removal of lymph nodes," Dr. Basuk says. It's very difficult to evaluate 30 or more lymph nodes accurately, much less remove suspicious ones completely. "Surgeons may not be getting the correct lymph node in their mapping tumor may be obstructing the lymph node."

Accordingly, she says, "Recent studies have shown ultrasonography of the lymph node basin provides more accurate diagnosis of macroscopic and microscopic disease over SLNB. So why do SLNB when you could use ultrasonography?"