For the first time, scientists have been able to track, over a prolonged time period, the movement of cancer-killing cells injected into a patient as part of his medical treatment.

The study does not yet show the effectiveness of the injected cells in killing tumors, but scientists are enthusiastic about the initial findings.

"This has never been done before in a human," Dr. Sanjiv Gambhir, director of Stanford's Molecular Imagining Program, said. "Until now, we've been shooting blind — never knowing why the failed therapies didn't work. Did the cells die? Did they not get to where we wanted them to go? Now we can repeatedly monitor them throughout their lifetime."

Gambhir and his colleagues tested the technique in a middle-aged man with an aggressive brain tumor who was enrolled in a clinical trial at the City of Hope cancer center in Los Angeles. City of Hope and UCLA researchers performed the study with Gambhir, a professor of radiology and a faculty member of Stanford's Cancer Center.

Results of the work were published online Tuesday in the journal Nature Clinical Practice Oncology.

In the study, researchers were able to determine that injected "T" cells not only homed in on the brain tumor, but also migrated to another area of the patient's brain to highlight a second, previously undetected tumor site.

U.S. Food and Drug Administration researchers also participated in the study. Other Stanford researchers involved in the work were Shahriar Yaghoubi, Shradha Budhiraja and David Paik.

The research was funded by the Doris Duke Charitable Foundation, the National Institutes of Health and the National Cancer Institute.

— Don Kazak

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