Could an experimental pill become the next best diagnostic tool for breast cancer?
According to the Centers for Disease Control and Prevention (CDC), in 2014 alone — the latest year for which complete data are available — 236,968 women and 2,141 men in the United States received a breast cancer diagnosis.
But, in many cases, it is difficult to distinguish between malign and benign tumors, or between fast-progressing forms of cancer and those that are so slow to develop that they will not severely affect someone during their lifetime.
Moreover, dense breast tissue can sometimes get in the way of locating and diagnosing existing tumors, which may remain undetected for a long time.
And, a lack of clarity when it comes to the initial diagnosis can lead health practitioners to refer patients for further procedures, which can be invasive and may be unnecessary. So what if there was a better, more accurate way of diagnosing breast cancer — one that would eliminate the stress and cost of treatments that may not even benefit the patient?
Researchers from the University of Michigan in Ann Arbor have now developed a pill that, once ingested, acts as a molecular imaging agent, allowing specialists to obtain more precise information on the location and type of tumors.
Safer, more precise diagnostic tool
"We overspend 4 billion [dollars] per year on the diagnosis and treatment of cancers that women would never die from," notes lead researcher Greg Thurber.
But, he adds, "If we go to molecular imaging, we can see which tumors need to be treated."
The research team has, so far, conducted an experimental study on mice that has yielded promising results. A detailed account of the scientists' findings has now been published in the journal Molecular Pharmaceutics.
The pill developed by Thurber and colleagues carries a special "dyeing" agent that marks tumors by responding to a molecule that is present in tumor cells, the blood vessels that fuel tumor growth, and inflamed tissue.
This "dye" becomes visible under infrared light, which can easily penetrate and "scan" the body without exposing it to some of the risks inherent in X-ray exposure, such as DNA mutations.
Once absorbed into the body, this marker not only reveals, with accuracy, where tumors are located, but also provides information about the type of tumor by rendering visible the different molecules found on the surface of tumor cells.
This can help specialists to differentiate between malign and benign nodules, as well as assess the type of cancer tumor.
Speaking of other benefits that an infrared dye-carrying pill would provide to patients, Thurber and team also note that it is a safer diagnostic tool than similar, injectable infrared dyes. That, they explain, is because some individuals can have severe adverse reactions to these injectable agents.
A challenging task
While pills that deliver macromolecules to tumors have been developed by other research teams, these have eventually proved inefficient in clinical trials.
Numerous challenges stand in the way of designing a medium that effectively bypasses the body's gateways to the bloodstream, to deliver chemical agents where they are needed.
In the case of dye-carrying pills, the obstacles are particularly complex, as Thurber observes:
"To get a molecule absorbed into the bloodstream, it needs to be small and greasy. But an imaging agent needs to be larger and water-soluble. So you need exact opposite properties."
In fact, the current diagnostic pill "piggybacks" on the design of a cancer drug that did not make it through phase II clinical trials.
While the therapeutic agent, unfortunately, did not prove effective, the composition of the pill was ideal for carrying macromolecules to the bloodstream, so they could "find their way" to any existing tumors.
"[The pill developed in the current study] is actually based on a failed drug," Thurber explains. "It binds to the target, but it doesn't do anything, which makes it perfect for imaging."
In this proof-of-concept study, the researchers worked with a mouse model for breast cancer, and they were pleased to note that the pill worked as it was supposed to, delivering the infrared dye to the relevant tumor sites and marking the nodules.
This means that the macromolecule contained in the pill was able to survive the acidic environment of the stomach; also, it was not "flushed out" by the liver, eventually allowing it to pass into the bloodstream and do its intended work.