Northwestern University chemist Thomas J. Meade means no disrespect to his medical colleagues, but when he looks at the state of the art in diagnostics, he suggests that, for some procedures, physicians might as well use “stone knives.” Take, for example, mammography. “You know going in that there’s a one in five chance of a false positive or a false negative. You have an x-ray that’s not even smart enough to differentiate a shadow cast by a calcium spot from a tumor. After reading the film and seeing a shadow, they do the prudent thing and stick a 16-gauge needle in you for a biopsy. Then you have to spend the next five days freaking out that you’ve got breast cancer until you get the results,” he says.Some of Meade’s annoyance stems from the fact that his wife endured just such a false alarm-as will an estimated quarter to half of all women who undergo annual mammogram screening over the course of 10 years. But Meade’s criticisms go well beyond the specific failings of mammography and breast biopsies; to him and a growing number of other medical researchers, today’s diagnostic tools are too uncertain and invasive-just too primitive. Working at select academic centers and industrial labs around the world, these researchers are developing a suite of new tools that will enable doctors to spot disease instantly and accurately, without ever taking a scalpel or biopsy needle to their patients’ skin.
The new discipline is called “molecular imaging,” and it is fundamentally altering physicians’ ability to view the body and its processes. Most conventional imaging tools, from x-ray to magnetic-resonance imaging, provide anatomical or structural information: is there a lump in the breast or a shadow in the lung? Molecular imaging goes beyond anatomical information to reveal functional data-the cellular activities that characterize tumor growth or inflammation, for example.
This is important because cancer and other diseases often begin with subtle cellular changes, well before a structural abnormality, such as a tumor, is detectable. What’s more, the new advanced imaging methods can help distinguish between diseases that look similar but actually involve different molecular malfunctions-and thus require different treatments. “Disease is being redefined in terms of its molecular signature,” explains Daniel Sullivan, associate director of the National Cancer Institute and head of the institute’s biomedical-imaging program. “In the future, people will talk about cancer by the molecular abnormality, not by the organ of origin.”
And in the future, molecular imaging could be integral to every step of health care. Exquisitely sensitive periodic scans could flag any worrisome changes-the presence of a particular protein associated with the beginning of a cancer, for instance. Should doctors eventually spot a lesion, the imaging process itself would yield enough information about the biochemical malfunction not only to make the diagnosis without a biopsy, but also to help determine the best therapeutic option. Still more noninvasive imaging would closely track the treatment’s progress and the course of the disease.
It might take 20 years or more for this complete picture to emerge. But the first generation of technologies to make it possible is already appearing. Thanks to advances in a range of disciplines, from molecular biology to optics to computation, researchers have begun to design chemicals that, once injected into the body, swarm to particular molecules associated with certain diseases and light them up, allowing physicians to easily spot problem areas.
More than half a dozen such molecular-imaging agents are now on the market, most of them for cancer diagnosis; another handful are in clinical trials, and even more are in the development pipeline. Targets for these new diagnostic tools include not only cancers but cardiovascular disease and ills of the central nervous system. “All these technologies are growing incredibly rapidly,” says Harvard Medical School radiologist Umar Mahmood, a principal investigator at Massachusetts General Hospital’s Center for Molecular Imaging and Research. “We’re not doing incremental work. These are leapfrog advances.”
Indeed, it’s a big enough jump forward that government, the established diagnostics industry, and a few venture capitalists are making substantial investments in the field. The National Cancer Institute has designated molecular imaging an “extraordinary opportunity,” spending more than $100 million on it in recent years and asking for $78 million in 2004. To keep up, companies like General Electric-which already has a $9 billion business in conventional medical imaging machines and systems-are venturing further into molecular biology and chemistry and inking deals with major pharmaceutical companies and startups to develop new imaging agents (see “A Snapshot of Molecular-Imaging Companies,” bottom). For the industry and patients alike, says Eric Stahre, general manager for genomics and molecular imaging at GE Medical, “molecular imaging has the potential to change the game.”
|A Snapshot of Molecular-Imaging Companies|
|GE Medical Systems |
|Imaging instruments and agents||GlaxoSmithKline, Amersham Health|
(St. Louis, MO)
|Nanoparticle imaging agents for cancer and heart disease||Dow Chemical, Philips Medical Systems|
(San Diego, CA)
|Imaging probes for neuro- degenerative, cardiovascular, |
and liver diseases
|University of Wisconsin, Vanderbilt|
|Molecular Insight |
|Imaging agents designed to identify heart damage||Harvard University, Syracuse University, Georgetown University|
|Theseus Imaging |
|Imaging agents for cancer and heart disease||Philips Medical Systems|
|Xenogen (Alameda, CA)||Optical imaging in animal models of disease||AstraZeneca, Biogen, Bristol-Myers Squibb, Chiron, Eli Lilly, Millennium, Novartis, Pfizer|