Fluoride-labeled Boronophenylalanine PET Imaging in Patients With Solid Tumors

Overview

Recently, new high-dose radiation therapy \[e.g., boron neutron capture therapy (BNCT)\] absorbed into the tumor tissue has been applied to treat patients with solid tumors. Here we examine and describe how to evaluate the biological activity of tumors using positron emission tomography (PET) with fluoride-labeled boronophenylalanine (F-BPA) as a tracer.

Boron Neutron Capture Therapy（BNCT） is an advanced cell-scale binary targeted radiotherapy technology that combines the advantages of targeted therapy and heavy ion therapy. BNCT provides a neutron source from a reactor or a medical accelerator. At the same time, the patient needs to be pre-injected with a boron-containing drug containing a non-radioactive boron 10 isotope. The boron drug enters the body and accumulates specifically in cancer cells. The patient receives epithermal neutron beam irradiation with high linear energy transfer (Linear EnergyTransferLET), thereby achieving the effect of killing tumor cells. Purpose，BNCT has more advantages over conventional radiotherapy, and normal tissue is better preserved than conventional radiotherapy. PET imaging is a useful and effective technique to give absolute quantitative and biological distribution data of BPA in a non-invasive manner, and can add important characteristic parameters such as T/N ratio, SUV and Kinetic parameters. Given the complexity of BNCT, PET and PET/CT is currently the new standard for designing patient recruitment: The Methodology of L-18F-BPA PET is an important tool to design clinical trials , estimate the size of tumor and indicate the concentration ratio of BPA in surrounding normal tissues. Following this principle, researchers can accurately identify which patients can benefit from BNCT treatment through the selective accumulation of BPA in individual tumors. PET scans can provide a three-dimensional map of the boron distribution, which can be used for macroscopic dose calculations in the BNCT conventional neutron transmission code. Because most of the dose absorbed by living cells (65%) comes from the 10B(n,a)7Li response, the distribution of boron determines the variability of the main absorbed dose in the treatment plan. As a result, therapeutic schedule will be improved because the boron distribution will greatly affect the isodose line. Routine calculations provide a wider range of isodose contours, whereas PET produces contours that more closely approximate the observed clinical results of BNCT.

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