Doctors running souped-up MRI machines may now be able to predict outcomes for chemotherapy -- before they prescribe the caustic treatment to their patients with cancer.
That's the case being made this week by Israeli physicist Dr. Yael Mardor, who is using a technique called high diffusion-weighted magnetic resonance imaging (DWMRI) to measure the velocity and mobility of water molecules within cancer cells.
Medical personnel use standard MRI to take pictures of patients' internal organs without using ionizing radiation.
Mardor, speaking on Monday at a medical conference in Nice, France, said the mobility, or diffusion, of water molecules in cancer cells can tell doctors whether a tumor will respond to chemotherapy.
Doctors already use DWMRI to diagnose strokes, and Mardor has employed the method to measure the effectiveness of cancer therapies in the early stages of treatment.
"But this is the first proof we have," Mardor said, "that a high DWMRI can predict what might happen to a tumor before treatment has begun."
In a recent experiment at the Chaim Sheba Medical Center, Mardor captured MRIs -- about 50 to 100 milliseconds apart -- of water molecules moving about in the cancer cells of mice.
The images showed the diffusion of the water molecules in the cancer cells. They also showed the intracellular water volume of the cells, which indicates their responsiveness to chemotherapy.
"Viable cancer cells, which tend to have higher water volumes, respond better to chemotherapy than those that are necrotic (dead and dying)," Mardor said.
Doctors may be able to use high DWMRIs to formulate individualized treatment plans, Mardor said. Follow-up images a few days into treatment would tell if the treatments are working as expected.
"The sooner we can determine that a treatment isn't working, the better," Mardor said. "We want to be trying other approaches instead of killing the patient with the chemotherapy."
Before Mardor can take the technique into the clinic, however, she must face DWMRI's most significant drawback: its extreme sensitivity to a patient's slightest internal movements.
"DWMRIs are very sensitive to bulk motion in an object," said Arthur Gmitro, a professor of radiology and optical sciences at the University of Arizona.
That can make examining the heart, lungs, liver and bowels almost impossible with DWMRI, Gmitro said.
Gmitro also suggested that small, heterogeneous tumors may be hard to examine closely with a technique that measures water diffusion.
"Tumors often have many compartments, comprised of both viable and necrotic tissue," Gmitro said. "I can imagine it being hard to distinguish between the two in a DWMRI."
But many scientists, including those at the University of Arizona, are working on software that can push the resolution of MRI machines high enough to measure water diffusion within moving organs.
Mardor uses software from Harvard University to enhance her DWMRI output. And for the moment, she is limiting her human research to the brain, a fairly stationary organ.
The paper Mardor presented in Nice only covers her recent work with mice in the laboratory. But she plans to report on her test on human patients this spring.
"This is not yet a clinical application," she said, "but that is clearly where we are hoping to take this."
