This a story about a compound, chlorotoxin, derived from scorpions, which has properties that may make it useful to doctors to improve surgical treatment of tumors. Researchers used this toxin, which binds to cancer cells, to build a chemical marker that emits photons in the near-infrared spectrum that in turn can be detected by special cameras. It is hoped that such a technology will make surgical excision of tumors more precise and successful, leading to improved patient outcomes.
However the story provided an overly enthusiastic outlook for the potential of chlorotoxin to change cancer treatment. The idea that one might be able to improve the surgical removal of tumors is exciting, but this ought to be tempered with an understanding that while it sounds like a good idea, it has not yet been shown to actually make any difference in terms of prognosis. In fact, the studies have all been conducted in mice or using cells in culture. No experiment has been reported where the compound was used to define the tumor containing portion of the tissue and the animals in which it was used lived longer, for example. It still remains to be determined whether the compound can be safely used in humans. And the equipment for visualizing chlorotoxin in the body does not yet appear to be available in a size large enough to accomodate a person.
So while the story did transmit the excitement about a new technology that might be useful during cancer surgery, it failed to provide balance with reasonable caution about over-optimism engendered by such pre-clinical findings limited to lab animals. Although it’s interesting to learn about chlorotoxin, it is premature to draw any conclusions about its utility.
There was no mention of costs of the "paint" nor of the equipment needed to visualize where the "painted" cells are localized.
From the website of the company that made the imaging equipement, it was not apparent that an apparatus was even available that would accomodate a "patient" larger than a rodent.
The "paint" was touted as having use for identifying "the micrometastases that can make breast cancer so dangerous" although it is not clear that it would be sufficiently sensitive for this purpose. More importantly, the implication is that detecting these would automatically mean a difference in terms of outcome (decreased morbidity or increased mortality) – however there is no evidence to suggest that this is the case.
There was no discussion of possible harms of this experimental approach. In the study, there was a failure of detection in one instance because of normally occuring material which gave off the same light as the "paint". This would be an example of a false positive test; there may be other instances where something similar could occur. How often does this occur?
This is an example of an animal research report being presented as applicable to humans. There is little, if anything, known about potential harms in human subjects.
The story explained that the study it reported on involved examining cancers in mice. However, it stated that the "paint" was tested in a variety of human tumors grown in mice. It should have said a variety of the kinds of tumors that occur in humans rather than human tumors. Only one of the tumor lines tested was of human origin. The other 4 were all of rodent origin.
While the "paint" may provide a better way to distinguish between health and cancerous tissue, it is not clear that it results in a significant difference of normal tissue being left undisturbed or in a more complete excision of cancerous tissue. The results presented to date are too preliminary to know.
The first sentence where the story states that "….there’s nothing as important as making sure that every last bit of disease has been removed", along with the threat of "spreading malignancies" is disease mongering. One might reasonably argue that there is nothing more important than leaving sufficient intact brain or other tissue undisturbed.
The only quote is from the senior author of the research study (Cancer Research 2007; 66(14):6882-6888). The story could have provided views of surgeons or other researchers who work with current technologies. How does the National Cancer Institute or a cancer research organization assess this research?
The story did not do an adequate job of describing this experimental approach and did not provide any information about the techniques currently in use for determining tumor margins. It is not a foregone conclusion that this technology would outperform other methods such as sequential sampling of tumor margins with intra-operative microscopic examination.
The story mentioned that testing of the "paint" described in the research would be expected to begin next year. Presumably these would be tests to determine effectiveness; before that there would need to be tests conducted to determine whether it is safe for use in humans.
It is not clear that the equipment (Xenogen IVIS-100 system) needed to visualize the "paint" in patients is available.
In general, the leap that is required from animal research to possible human application is not well explained.
The story was correct in presenting the "paint" as a new possible adjunct to the methods used for determining tumor boundaries.
We can’t be sure if the story relied largely or solely on a news release, but it is clear that the story quotes only one researcher from only one hospital.