Tumor "Painting" with Scorpion-Derived Substance Beats MRI for Brain Surgery

A special "paint" made from substances found in scorpions is the latest advance in the battle against cancer, according to Seattle Children's Hospital Research Institute. The substance, which causes tumor cells to "glow" in the near-infrared spectrum, has already been shown to have applications for many types of cancers, and has accuracy many times better than existing MRI technology in identifying tumors. The most significant application may be in brain cancers, where the difficult and subtle identification of cancerous brain tissue is vastly improved. As the institute notes, "Until now there has been no way to allow surgeons to see tumors 'live' during surgery."

The potential of the paint has already been demonstrated in a mouse model, where it was used to identify brain tumors only 1 millimeter across without including surrounding normal brain tissue. The announcement indicates that a prostate cancer model, as few as 200 cancer cells in a mouse lymph channel could be identified.

The research institute is especially excited about the potential for brain cancer surgery, where several challenges exist. They note that "approximately 80% of malignant cancers recur at the edges of the surgical site," and there is difficulty in removing the entire tumor without removing amounts of normal brain tissue. In the past, surgeons relied on subtle indicators such as blood flow and color and texture differences to determine tumor location. Since the tumor paint can identify groups of cells as small in number as 2000 while MRI technology needs at least 1 million cells to identify an area to be removed, the surgeon can perform his or her job with greater accuracy and better outcome.

The painting substance, called Chlorotoxin:Cy5.5, is fast-acting, working within minutes to begin emitting a signal. While currently used contrast agents fade after a few minutes, the paint's signal lasts for 14 days. An article in Radiology discusses the potential drawbacks of contrast agents, which are significant.

The institute notes that surgery is still an important form of cancer therapy, and because of subjective methods of identifying tumors, the visual indication given by the paint should result in significant reductions in preventable cancer growth and patient mortality.

The substance is undergoing toxicity studies and other preparations to apply for approval from the FDA for clinical trials on consenting adult humans. The researchers believe that the paint could be used as a early screening tool for skin, cervical, esophageal, colon and lung cancers. As in the mouse model, identifying cancer in lymph nodes might contribute significantly in the areas of breast, prostate and testicular cancer as well.

The researchers involved in the development of the substance are associated with Seattle Children's Hospital Research Institute and Fred Hutchinson Cancer Research Center.

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Peter Reimer MD, Radiology, "Tumor-targeted MR Contrast Agents: Hype or Future Hope", http://radiology.rsnajnls.org/cgi/content/full/231/1/1