New imaging agent helps to locate lymph nodes

According to a statement issued today by the U.S. Food and Drug Adminstration, the agency has approved a product called Lymphoseek (technetium Tc 99m tilmanocept) Injection, which is a radioactive imaging agent that helps doctors locate lymph nodes in patients with breast cancer or melanoma who are having surgery to remove tumor-draining lymph nodes.

We are posting this notification because there will probably be a good deal of media coverage of this approval, and we want to make it very clear to prostate cancer patients that we are (as yet) aware of no data whatsoever to suggest that Lymphoseek will have applicability in the location of tumor-draining lymph nodes for men with prostate cancer.

Lymph nodes filter lymphatic fluid that flows from the body’s tissues. This fluid may contain cancer cells, especially if the fluid drains a part of the body containing a tumor. By surgically removing and examining the lymph nodes that drain a tumor, doctors can sometimes determine if a cancer has spread. When it comes to the management of prostate cancer, surgical removal of the lymph nodes can be done as one element in the conduct of a radical prostatectomy and it can also be done laparoscopically as an independent surgical procedure.

To quote the FDA’s statement, “Lymphoseek is the first new drug used for lymph node mapping to be approved in more than 30 years.” However, “Lymphoseek is an imaging drug that helps locate lymph nodes; it is not a cancer imaging drug.”

According to Dr. Shaw Chen of the FDA, “Removal and pathological examination of lymph nodes draining a primary tumor is an important diagnostic evaluation for some patients with breast cancer or melanoma. … To use Lymphoseek, doctors inject the drug into the tumor area and later, using a handheld radiation detector, find lymph nodes that have taken up Lymphoseek’s radioactivity.”

The most common side effects identified in clinical trials of Lymphoseek in people with breast cancer melanoma have been pain or irritation at the injection site.

Now, having made the above clear, we should say that it may well be helpful to use Lymphoseek in men with prostate cancer because it may make it easier to identify and therefore remove selected lymph nodes and then examine those nodes pathologically for signs of prostate cancer. We assume that there will be studies carried out to investigate that possibility in the near future. There is already a trial being conducted to explore the utility of Lymphoseek to help locate lymph nodes in patients with squamous cell cancers of the head and neck.

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