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The U.S. Food and Drug Administration (FDA) has approved Lymphoseek® (technetium Tc 99m tilmanocept) Injection, a radioactive diagnostic imaging agent that helps doctors locate lymph nodes in patients with breast cancer or melanoma who are undergoing surgery to remove tumor-draining lymph nodes.

Approximately 232,000 new cases of breast cancer and 77,000 new cases of melanoma are diagnosed annually in the United States. Lymphatic mapping is a procedure in which lymph nodes that may contain tumor metastases are identified and biopsied to determine if cancer has spread beyond the primary tumor. Accurate staging of lymph nodes is critical, as it guides treatment decisions and determines patient prognosis and risk of recurrence.

Lymphoseek is a receptor-targeted, small-molecule radiopharmaceutical imaging drug that helps locate lymph nodes. It is designed to identify the lymph nodes that drain from a primary tumor, which have the highest probability of harboring cancer, in patients with breast cancer or melanoma. After injecting the drug into the tumor area, doctors use a handheld radiation detector to find lymph nodes that have taken up Lymphoseek’s radioactivity.

The safety and effectiveness of Lymphoseek were established in two clinical trials of 332 patients with melanoma or breast cancer. All patients were injected with Lymphoseek and blue dye, another drug used to help locate lymph nodes.

Surgeons subsequently removed suspected lymph nodes for pathologic examination. Confirmed lymph nodes were examined for their content of blue dye and/or Lymphoseek. Results showed that Lymphoseek and blue dye had identified most lymph nodes, although a notable number of nodes were identified only by Lymphoseek. The most common side effect associated with Lymphoseek was pain or irritation at the injection site.

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Lymphoseek is the first new lymph node mapping drug to be approved in more than 30 years. Other FDA-approved drugs used for lymph node mapping include sulfur colloid and isosulfan blue.


FDA approves Lymphoseek to help locate lymph nodes in patients with certain cancers. [FDA News Release]. U.S. Food and Drug Administration website. Available at:

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