Novel PET Imaging in cancer

Aarntzen, Erik

Current biomarkers are unable to adequately predict vaccine-induced immune protection in humans with infectious disease or cancer. However, timely and adequate assessment of antigen-specific immune responses is critical for successful vaccine development. Therefore, researchers from the department of Tumor Immunology Lab, Medical Oncology and Nuclear Medicine have explored positron emission tomography (PET) imaging to assess immune responses in vivo in a clinical setting. Melanoma patients with lymph node (LN) metastases received dendritic cell (DC) vaccine therapy, injected intranodally, followed by [18F]-labeled 3'-fluoro-3'-deoxy-L-thymidine ([18F]FLT) PET scan at varying time points after vaccination. De novo immune responses were readily visualized in treated LNs early after the prime vaccination and these persisted for up to weeks. This selective [18F]FLT uptake was markedly absent in control LNs, which received saline or unloaded DCs. Furthermore, tracer uptake increased profoundly with as little as 4.5×105 DCs per LN, highlighting the sensitivity of PET scans for imaging functional processes. Importantly, the level of LN tracer uptake significantly correlates to the level of circulating antigen-specific IgG antibodies and antigen-specific proliferation of T cells in peripheral blood. Therefore, [18F]FLT PET offers a sensitive tool to study the kinetics, localization and involvement of lymphocyte subsets in response to vaccination. This allows for early discrimination of responding from non-responding patients in anti-cancer vaccination and aid physicians in individualized decision-making.

Aarntzen et al., Early identification of antigen-specific immune responses in vivoby [18F]FLT PET imaging. PNAS 2011


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