Phase 2 Clinical Trial Detects Hidden Multiple Myeloma via Targeted ImmunoPET
A targeted immunoPET scan detected active multiple myeloma that standard PET/CT scans and blood tests missed, according to a phase 2 clinical trial led by researchers at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine. The imaging approach uses labeled antibodies that bind directly to myeloma cells, potentially improving disease mapping and therapy evaluation for patients.
More than 36,000 Americans are diagnosed with multiple myeloma each year. Standard care tracks progression using glucose-based PET/CT scans, which assume tumor cells consume larger amounts of glucose than surrounding tissue. However, C. Ola Landgren, chief of the Myeloma Division and director of the Sylvester Myeloma Institute, noted that myeloma cells frequently consume normal amounts of glucose. As a result, standard PET/CT scans miss residual disease in up to 40% of cases.
Antibody-Based Scanning Reveals Hidden Lesions
To address diagnostic gaps, researchers developed a compound using antibodies designed to recognize CD38, a myeloma-specific surface protein. After testing the idea in laboratory models and early human studies, the team enrolled 60 multiple myeloma patients in a multicenter phase 2 clinical trial. Participants underwent both standard glucose-based PET/CT scans and the new antibody-based immunoPET scans.
More than 10% of trial participants showed disease signals exclusively on the immunoPET scans. Follow-up biopsies confirmed that these signals represented active multiple myeloma. In one instance, a patient with persistent back pain and normal blood markers showed spine lesions on the immunoPET scan, prompting a treatment switch that resolved the pain. Another patient with negative standard tests and blood markers was found to have nearly 100 sites of disease across the body.
Comparing ImmunoPET and Standard PET/CT Performance
While immunoPET uncovered disease missed by standard scans in 17 patients (28%), the reverse occurred in 13 patients (22%), where standard PET/CT detected disease that immunoPET missed. Both imaging methods detected comparable amounts of disease in the remaining trial participants. Landgren emphasized that no single test identifies every case, meaning immunoPET functions as an additional layer of information rather than a replacement for existing tools.
The current version of the scan requires a week for the antibody to circulate and bind to cancer cells. Researchers are currently developing smaller antibody fragments to speed up tumor targeting, which could eventually enable a same-day test for routine clinical use.
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