Oncological Prognosis of Prostate Lesions by Chemical Exchange Saturation Transfer Magnetic Resonance Imaging (CEST-MRI)

Prostate cancer is the second most common type of cancer in men only after lung cancer, and accounts for \~3.8% of all deaths caused in men in 2018. Multiparametric MRI, which combines anatomical MRI sequences (T2-weighted acquisitions) and functional sequences (DWI Diffusion-Weighted Imaging or dynamic contrast-enhanced (DCE) acquisitions), constitutes a key tool in the detection and monitoring of the therapeutic response in the context of the management of this prostate cancer. In this context, a recognized radiological consensus has been established in order to standardize MRI acquisition protocols and the data processing scheme (Prostate Imaging Reporting and Data System, PI-RADS protocol). Although the improvement provided by multiparametric MRI is significant for the detection of prostate cancer in the clinic, approximately one third of cases remain equivocal. There is therefore a clear clinical advantage in having additional information to support the diagnosis by discriminating between low-grade, intermediate-grade and high-grade tumors and thus reduce the need for biopsies. CEST (chemical exchange saturation transfer) MRI is a promising molecular imaging tool for specifically detecting metabolites containing exchangeable protons present on amide, amine or even hydroxyl functions. MRI-CEST allows non-invasively to highlight molecules of interest such as lactate, glutamate, citrate and other mobile proteins and peptides involved in the carcinogenesis process and usually impossible to visualize by MRI or MRS (Magnetic Resonance Spectroscopy). Exchangeable protons also have the property of seeing their exchange rates modified depending on the surrounding pH, making this CEST contrast sensitive to pH variations. Then, it is APT-CEST (Amide Proton Transfer CEST). The first efforts to translate this method from the preclinical to the clinic were made for brain imaging of gliomas with a significant contribution of APT-CEST in the stratification of tumors. Now, wor