A diagnosis of invasive breast cancer is typically followed with a check of the closest lymph nodes to see if the cancer has spread. A decade ago that meant tissue which amounted to the size of a softball. Now surgeons rely on lymphatic mapping to spot the nodes that might contain tumor cells. Neoprobe (Dublin, Ohio) has developed a radioactive tracing agent that permits the removal of tissue that's now the size of a grape. And, it's 97% predictive in determining if the cancer has spread. Positive data from a Phase 3 evaluation of that agent, called Lymphoseek, was presented last week at the International San Antonio Breast Cancer Symposium.

"We're very optimistic because we believe the market potential on global basis is about $350 million to $370 million," Brent Larson, Neoprobe VP and CFO told Medical Device Daily. "For a company like ours, which is doing $8 million in device sales, it's a prospective-changing technology for us."

Those data have been submitted for FDA review.

The Phase 3 study was conducted in 130 patients with either breast cancer or melanoma. The San Antonio presentation provided information on the breast cancer portion of the trial which included 60 patients, but those results mirrored the overall results, according to Neoprobe.

The trial was intended to determine the accuracy of Lymphoseek to identify lymphatic tissue as compared to a commonly used vital blue dye. The primary objective was to obtain at least 203 lymph nodes identified with the vital blue dyes and to statistically demonstrate that 94% of those nodes were identified with Lymphoseek. The procedure-compliant patients contributed 215 vital blue dye positive lymph nodes and Lymphoseek identified 210 of those nodes for a success rate of 97%. Additionally, Lymphoseek identified 85 lymph nodes that were missed by the vital blue dyes. Of those Lymphoseek-only positive nodes, 18% were found to contain tumor.

"About 15 years ago, surgeons started to experiment using intraoperative Geiger counters. They injected a radioactive agent near the tumor to follow the likely spread path of cancer," Larson said. Neoprobe developed its own version of a Geiger counter, called the Neoprobe GDS line of gamma detection systems on the market now for almost a decade.

But along with that system surgeons used radioactive agents off label (typically technetium-99) that didn't produce the most specific results.

"About five years ago, we started working with the University of California, San Diego, to develop a drug that's more specific," he said. "These Phase 3 trials have shown that we may have developed a better mousetrap. It has better performance in clear time. It attaches to and stays in the sentinel node. The off-label drug we use now (technetium-99) doesn't stay in the node. We believe Lymphoseek is a better product. We're very optimistic that we've got something going here that will improve the procedure."

The study's primary endpoint was to show equivalence to the visual tracing agent vital blue dye. Ninety percent of the time, surgeons will use technetium-99 and a visual blue dye so they know, after resecting, that they are removing lymphatics and not other tissue. The endpoint was intended to show a 94% concordance rate in lymph nodes removed and we met and exceeded it with a 97%.

"We see this being used in solid tumor cancers that drain through the lymphatics, including a lot of gastrointestinal cancers, ovarian and prostate," Larson said. "They all spread through lymphatics, but the off-label drug isn't effective because blood vessels are so much smaller that the agent doesn't go through. We've got a much smaller molecule and we believe that particle size will enable us to get into a lot of other cancers."

Lynn Yoffee; 770-361-4789