The radiologists presented findings from a trial at the 2005 Annual Meeting of the American Society of Clinical Oncology, or ASCO, held May 13-17.
Called radioimmunotherapy, the emerging treatment allows physicians to target radiation straight to patients' cancer cells from within the body, rather than through external beams.
Radioimmunotherapy joins radioactive atoms to special antibodies. These antibodies are injected into the body, where they deliver their radioactive payload by seeking out and binding to proteins found on cancer cells. Selected institutions have been offering this treatment to non-Hodgkin's lymphoma patients since the early 2000s.
However, in a few patients, the medication goes to the wrong tissues. That means that physicians are required to perform numerous imaging scans to monitor patients at the start of therapy, a process that lengthens and complicates treatment. If physicians could quickly confirm that medication is going where it should, that would speed treatment while maintaining quality care for patients.
"This treatment approach is growing, and is a new and realistic alternative to conventional chemotherapy. Making it easier for physicians to administer the treatment by avoiding unnecessary steps will lead to higher utilization and better patient compliance," said Peter Conti, M.D., professor of radiology at the Keck School, director of the USC PET Imaging Center and first author on the ASCO presentation. He noted that patients receive injections on an outpatient basis and have an overall high level of satisfaction with the procedure.
So researchers from the Keck School of Medicine and San Diego-based Biogen Idec Inc. studied about 400 patients who had received Zevalin, a type of radioimmunotherapy, between 2002 and 2003. Biogen Idec Inc. developed Zevalin. All patients had unsuccessfully tried other conventional therapy first.
Zevalin consists of a series of steps. In the first line of attack, physicians infuse rituximab, a monoclonal antibody that hones in on B cells, the immune cell most often involved in non-Hodgkin's lymphoma. Next, for the imaging sessions, physicians inject another monoclonal antibody, ibritumomab tiuxetan, which is specially tagged with a radioisotope known as indium 111. Finally, a week later-and only if imaging sessions have shown the medication accumulating in the right areas-they inject ibritumomab tiuxetan that has been tagged with another radioisotope called yttrium 90.
After the injections of ibritumomab tiuxetan with indium 111, physicians today perform an imaging scan within 24 hours of the injection and then again within two to three days to verify that the radioactivity is going to the cancer sites. Some even perform more scans four to five days later.
But Conti and colleagues found that most of those scans are unnecessary.
In their study, they saw that 16 patients had treatment discontinued due to results on imaging scans. Of these, only six who had their treatment halted actually had medication going to the wrong tissues. And most importantly, all of these cases were apparent after the very first imaging scan.
The findings suggest that physicians and patients can confidently proceed with treatment if radioimmunotherapy is correctly targeting cancer-ridden areas based on scanning within 24 hours of the indium 111-labeled Zevalin.
Conti is currently planning further radioimmunotherapy trials at USC, including a potential trial for AIDS-related lymphoma done in conjunction with hematology faculty.
Because Conti reviewed patient data from Biogen Idec's original clinical trials with Zevalin, the research was supported in part by Biogen Idec.
Peter Conti, Christine White, Peter Pieslor, Gene Menendez, V. Douglas Harrough, Dan Matso, Jacqueline Aussie, Thomas Ryskamp and Paul A. Foster, "Low Frequency of Altered Biodistribution Detected by Indium 111 (111In) Imaging Prior to Yttrium 90 (90Y) Ibritumomab Tiuxetan (Zevalin) Radioimmunotherapy: Results from a Zevalin Imaging Registry," American Society of Clinical Oncology 2005 Annual Meeting, May 13-17, 2005, Poster Session Abstract No. 6589.