In rare cases, it is possible for both blue dye and radiotracers like Lymphoseek to fail to mark a cancer-positive SLN, Dr. Wallace cautioned.

“When there’s nothing hot or blue in the pathologically-positive lymph node, it is usually because the positive lymph node has so much tumor in it that the lymphatics have shut off,” she explained. “Usually a good surgeon can pick that lymph node out anyway, because it’s so hard, once your fingers are near it, you’ll feel it. That’s why the definition of the sentinel node is ‘anything hot, anything blue, or anything hard.’ Because, you know, the hard lymph nodes mean they’re chock full of tumor.”

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Few Toxicities for Lymphoseek —But Watch for Hypersensitivity Reactions

Lymphectomy procedures including SLN biopsy are associated with a risk of lymphedema, but Navidea reports “no clinically significant drug-related adverse reactions” to date on its company website.

While blue dye involves a “well-documented but rare” risk of allergic reaction, radiocolloids and Lymphoseek do not have appreciable toxicities, Dr. Sondak said.

“The only thing we noticed with any tracer is that it hurts to get a shot,” Dr. Sondak said. “They have radioactivity so you have to be careful in a pregnant or breastfeeding woman, but there is no difference between the radiolabeled colloid or Lymphoseek in that regard.”

While no serious adverse reactions to Lymphoseek were identified in the clinical trials, it might still pose a risk of hypersensitivity reactions because of its molecular similarity to dextran, Dr. Pykett cautioned.  Serious hypersensitivity reactions have been associated with dextran and modified forms of dextran in other drugs. Patients should be asked about any previous hypersensitivity reactions to drugs, particularly dextran or modified forms of dextran, prior to Lymphoseek injection, Navidea advises.

In addition, “Resuscitation equipment and trained personnel should be available at the time of Lymphoseek administrations, and patients observed for signs or symptoms of hypersensitivity following injection,”notes a Navidea press release.

An Optimistic Future Ahead?

Navidea is studying Lymphoseek’s efficacy in lymphatic mapping among patients with cancers other than breast cancer or melanoma, Dr. Pykett noted. The company is preparing to release data later this year from an interim analysis of Lymphoseek’s use in head and neck squamous carcinoma, he told

Navidea will also be studying Lymphoseek’s usefulness in colorectal, prostate, lung, and ovarian cancers, Dr. Pykett said.

Lymphoseek is likely to be just “the first in a long line of specific-targeted imaging, which goes along with targeted care for the patient,” Dr. Wallace said. “We are already starting to target treatment to the patient’s cancer. Targeting the imaging to the patient’s cancer as well is where things are going.”

Investigational modification of Lymphoseek for different imaging modalities is being studied, Dr. Wallace added.