There are no guarantees when it comes to chemotherapy.
Many cancer patients endure excruciating side effects only to learn that their tumors have resisted their prescribed treatment from the start.
UCLA researchers recently took a step toward developing a noninvasive screening method that may help predict who can and cannot benefit from certain chemotherapy drugs, which would potentially save time, resources and unnecessary suffering.
The UCLA scientists detailed their findings in a paper published last week in the Proceedings of the National Academy of Sciences.
“It was pretty exciting,” said Rachel Laing, a molecular and medical pharmacology graduate student and one of the authors of the study. “We wanted to show that we have this new tool … that we can use in an animal model to basically distinguish between responders and nonresponders.”
The scientists injected a recently developed molecular probe into mice with lymphoma and leukemia and watched its path as it encountered tumors, looking to see if the cancerous cells allowed the probe inside, Laing said.
Attached to the probe, a radioactive atom glowed when viewed under a noninvasive imaging scan known as positron emission topography, allowing researchers to follow the probe within live mice, she added.
Laing said that inside the body, the probe acted as a harmless mimic of gemcitabine, a commonly used chemotherapy drug that must enter tumor cells to have a chance of slowing or reversing the cancer.
“Any cells that take up the probe, we hypothesize that they’ll also respond and take up gemcitabine,” Laing said.
The research revealed that the probe did in fact enter tumor cells normally permeable to gemcitabine.
Laing said that the probe offered a preview of how cancer cells would likely react to gemcitabine without inducing any of the drug’s adverse side effects.
The findings are yet to be tested with other drugs and in other species, most notably humans, she said.
Laing added that the probe owed its effectiveness in large part to the powerful positron emission topography scanners that imaged its path.
Dr. Michael Phelps, the inventor of PET technology and the chair of the molecular and medical pharmacology department at UCLA, said that PET addresses a dilemma in modern medicine.
Phelps, who also co-authored the study, said that the research has shown that in all drugs used to treat illnesses ““ including cancer ““ on average, only about 20 percent of patients experience quantitatively positive responses.
“People are trying to move forward to a new world where when you develop a drug, you also have a diagnostic test that selects the patients for that drug,” Phelps said. “The most productive way to do that right now is in fact with PET, and this (study) is just one more example.”
Although encouraging, the study leaves a handful of questions unanswered, said Caius Radu, an assistant professor of molecular and medical pharmacology and another author of the study.
The scientists still want to know whether their recent results can be replicated with other cancer types, using alternative chemotherapy drugs and with different radioactive probes, Radu said.
Eventually, he said, they want to see if the predictive benefits of chemotherapy probes extend to humans.
For now, though, Radu said the new probe procedure remains far from predicting whether cancer treatments will succeed in people.
“Practical … would be an overstatement. At this point we don’t know,” he said. “It just shows that it might be feasible.”