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

This prospective, single-center study will make it possible to evaluate the capabilities of CEST MRI to predict oncological prognosis by comparing it to the reference multiparametric MRI examination and to the anatomopathological analysis of samples taken from biopsies. When the patient presents a suspicion of prostate cancer identified by an increase in the blood concentration of Prostate Specific Antigen (PSA), he is usually seen in consultation by the urologist within the urology department of the University Hospital. It is during this consultation, after having informed the patient of the need to carry out an MRI to rule out or confirm the presence of a lesion, that the doctor will propose the study to the patient, inform him, and grant him a period of reflection, will answer all his questions and will jointly sign the consent with him if he wishes to participate. The imaging examination will be carried out a maximum of 6 weeks after the inclusion visit in the research slots of the 3T MRI at CHU Gabriel Montpied (Wednesdays and Fridays). Patients will follow the usual imaging protocol with first multiparametric MRI acquisitions including sequences with injection of contrast product (GADOLINIUM) then a CEST MRI sequence whose duration will not exceed 15 min. As part of the patient's classic course, if the presence of one or more lesions is proven, a sample of the lesion(s) is taken for an anatomopathological analysis which will give the degree of tumor involvement. The patient returns to the University Hospital approximately 4 weeks later for a consultation for the anatomopathological results and the proposal for subsequent management (monitoring or treatment). The following data will be noted: age, medical history, PSA level in the blood (nanogram / millilitre), PI-RADS score for each suspicious lesion identified on multiparametric MRI acquisitions, Extension assessment, Parameters measured from the CEST MRI sequence for each of the suspicious lesions: ATP-CEST rate (in arbitrary units), MTRasym, Guanidyl/APT ratio making it possible to assess tumor acidosis, Pathology of samples from the lesion(s): presence or absence of lesions or cancer cells, their number, extent and nature using the Gleason score. The main objective of this study aims to study the predictive properties of a CEST MRI in the tumor classification of prostate tumors, considering the presence or absence of lesions or cancer cells, their extent and their nature through the score of Gleason on pathological examination of biopsy specimens as dependent variable of interest and measurements on APT-CEST images as main explanatory variable. False negative rates, diagnostic sensitivity and specificity values and negative and positive predictive values will be presented with a 95% confidence interval. The concordance between anatomopathological examination and CEST MRI will be studied by estimating the rate of concordant cases and Kappa concordance coefficient. The usual inferential statistical tests will be considered: for comparisons concerning variables of a quantitative nature: Student's t test or Mann-Whitney test if the conditions for applying the t-test are not respected; for categorical parameters: Chi2 test or Fisher exact test. Particular attention will be paid in particular to the time between the MRI and the pathological examination (3 weeks on average).