Getting faster answers about cancer treatment

“One of the biggest problems in cancer treatment is trying to get rapid assessment to see if the treatment you’re using works,” said Anthony Shields, MD, PhD, professor of the WSU internal medicine department. He has developed a tumor-imaging technique that he believes will shave weeks off of the currently used method for determining the effectiveness of cancer treatments.

Now, he said, health professionals commonly order a CAT scan of a tumor at the beginning of a patient’s cancer-treatment regimen, and a repeat scan about two months later to determine whether the tumor has grown. “That’s actually fairly slow in terms of somebody who’s getting aggressive – and often toxic – therapy. It means the physician has to wait two months before actually determining whether the treatment’s doing the patient any good or any harm.”

However, he reported, “With some of the imaging techniques we’ve been developing, we’ve been able to see changes in response to treatment within one to three weeks. Ultimately we’re hoping these techniques will allow us to be able to know much earlier on if a particular treatment is working or whether we need to try something else.”

His research has centered on using positron emission tomography (PET) to pick up specially designed radioactive compounds that yield information about tumor growth. “My work has focused on labeled thymidine and related compounds that are used by the body in DNA synthesis, which is a requirement when cells grow. What we’re trying to do is actually measure how tumor cells, in particular, are growing and use that to help diagnose and measure the response to the treatment.”

With assistance from John Grierson, a chemist at the University of Washington, Shields spent several years analyzing a series of compounds before developing one that had the unusual combination of characteristics necessary for tumor-metabolism imaging. That compound is a labeled pyrimidine analog called [F-18]FLT. “We were looking for something that we could label chemically relatively easily, that had what we considered a radioactively long half-life, and that wasn’t broken down very fast in the body,” Dr. Shields explained.

The compound works wonderfully, he said, adding that they are already in phase I/II clinical trials. “We’re trying to identify which tumor types this will be effective in detecting, and see how this works as a very early predictor of a patient’s response to therapy.” So far, the results are very encouraging, he commented.

Dr. Shields’ research has been recognized by the National Cancer Institute of the National Institutes of Health, receiving three large grants from the NIH totaling more than $2 million over a five-year period. With chemist Thomas Mangner and physicist Otto Muzik of the PET Center at Children’s Hospital, he will continue his trials with FLT and will also investigate potential new compounds.