Radioactive tracing agent can identify tumor-draining sentinel nodes in breast cancer, melanoma patients

Researchers say a new kind of tracing agent is more accurate than current methods in helping identify tumor-draining sentinel lymph nodes in breast cancer and melanoma patients. That's the finding in a new study that appears in the online version of the Annals of Surgical Oncology.

"This is an important finding for both physicians, and patients," says Stanley Leong, M.D., M.S., F.A.C.S., Chief of Cutaneous Surgery at California Pacific Medical Center and the lead author of the study. "We are always trying to find better ways of identifying which lymph nodes are cancerous, this new approach does just that with great accuracy, almost 90 percent of the time, and without any apparent safety issues."

Dr. Leong and his team used Lymphoseek, a radioactive tracing agent developed by Neoprobe, to see how effective it was in mapping the spread of two solid tumor cancers - breast and melanoma - to surrounding or sentinel lymph nodes, the first nodes to receive lymph drainage from a tumor.

Lymphoseek was injected into 78 patients (47 of them melanoma patients, 31 breast cancer patients) 55 of whom then underwent imaging scans to map its movement through the lymph system. In more than 94 percent of these patients, Lymphoseek was able to identify a tumor draining lymph node before surgery.

In this Phase 2 trial Lymphoseek showed that it did not cause any reaction at the site of injection, reached the targeted sentinel nodes faster than existing methods and was less likely to spread beyond the targeted nodes to other more distant nodes.

Previous studies have shown that solid tumors, such as breast cancer and melanoma, use the lymphatic system to spread to other parts of the body, including some regional sentinel nodes. Identifying how far those tumors have spread and what nodes are affected can help identify how extensive the treatment needs to be and can potentially limit the number of nodes that need to be removed.

"Our goal as surgeons is to remove only those nodes we need to and to avoid removing those not showing any signs of cancer," says Dr. Leong. "Lymphoseek seems to be more accurate at giving us this information than other mapping methods and that can hopefully help patients avoid unnecessary surgery."

Existing methods for mapping the spread of these tumors are relatively accurate but are all "off label" in that they have not been approved by the Food and Drug Administration (FDA) for that use. Neoprobe is hoping that this trial will enable it to move forward in applying for FDA approval for Lymphoseek as the first tracing agent specifically radio-labeled for lymph node detection.