Sentinel lymph node biopsy helps detect microscopic spread of melanoma

Key Points

Houston - The surgical removal of the lymph nodes in patients who are found to have positive nodes after undergoing sentinel lymph node biopsy (SLNB) improves survival, compared to patients who have melanoma spread to lymph nodes when the disease is large enough to be felt with a physical examination, according to a surgical oncologist.

Since the technique of lymphatic mapping and SLNB was introduced almost two decades ago, it has come to represent a common practice of care to manage patients with stage I and II melanoma, according to Merrick Ross, M.D., chief, melanoma section and department of surgical oncology, and the Charles McBride Professor of Surgical Oncology at the University of Texas MD Anderson Cancer Center, Houston.

"Most people believe that the data support the concept that if there is microscopic disease in lymph nodes at the time of diagnosis, that over time if this disease is untreated, the cells would multiply and become big enough in the node that you can feel (it)," Dr. Ross says. "Once it is big enough that you can feel (it), the risk for disease spread elsewhere in the body goes up. As the node is growing, the lymph node is a potential source for metastases elsewhere in the body."

"By doing the SLNB, you can identify which patients have microscopic disease in the nodes and which do not," Dr. Ross says. "You can then treat the nodal disease early and prevent progression in the nodes."

There is the possibility, however, that patients who are node-negative relapse and die from melanoma because they don't have lymphatic spread of disease but instead have spread of the disease through the blood, Dr. Ross says.

MSLT-1

The Multicenter Selective Lymphadenectomy Trial (MSLT-1) found a statistically significant difference in five-year, disease-specific survival in patients who had wide excision and SLNB (with immediate lymphadenectomy in patients with a positive SLN), compared with patients who had wide excision followed by observation of regional lymph nodes (with lymphadenectomy only if there was nodal relapse).

Investigators found that among the patients with positive nodes, five-year survival was 72.3 percent in the active treatment group, compared to 52.4 percent in the observation group (p=0.007).

The study's investigators found the status of the sentinel node to be the most important predictive factor of relapse and survival. "The lymph node is a potential source for metastases elsewhere in the body," says Dr. Ross. "You want to identify which patients have microscopic disease and which do not."