Prospective Study on Oncologic Cerebral Imagery Contribution by 18F-FDOPA Position Emission Tomography (PET) in a Multidisciplinary Meeting Therapeutic Proposal When Caring for Patients Diagnosed Primary or Secondary Cerebral Tumors

In standard care for patients diagnosed with a primary or secondary (metastasis) cerebral tumor, there is currently complex clinical situations in which the clinic and Magnetic Resonance Imagery (MRI) do not allow for the medical team to arrive at a conclusive diagnosis. The therapeutic proposition requires then a delay in additional follow-up of at least 3 months in order to clarify the situation, with a potential delay in diagnosis and therefore therapeutic care. The contribution of cerebral molecular imagery could allow for new additional information to be brought in or to increase the confidence index in the diagnosis in order to comfort the therapeutic collective attitude proposed in the multidisciplinary meeting (MM).

3.4-dihydroxy-6-18F-fluoro-L-phenylalanine (18F-FD0PA), dopamine precursor amino-acid, Position Emission Tomography (PET), allows for the studying in vivo of the proteic transmembrane transport in gliomatous tissue; active transport happens through a sodic-independent canal, increased in malicious transformations, and in which kinetics can give an indication regarding the development of the primary tumor.

In MRIs, tumor tissue growth after injecting the contrast product translates to a rupture in the Blood-Brain Barrier (BBB), while tumor extraction from the radiopharmaceutical is independent of the state of integrity of the BBB and whose only function is metabolic tissue activity. This method of imagery thus appears as a promising contribution to conventional imagery.

Furthermore, different to 18F-FDG (18F-2-fluoro-2-deoxy-D-glucose fluorodeoxyglucose), similar to the largely used glucose in oncologic molecular imagery, exploration of harmful glioma in 18F-FDOPA, is not compromised by background noise activity, and is almost useless in a healthy cerebral cortex, with the exception of striatal physiological fixation used as a level of reference. The best performances in terms of positive and negative predictive value were defined in the literature with a tumor/striatum threshold of 1.

According to the latest and current European recommendations, turning to PET when caring for high-level gliomas patients can be proposed in the evaluation of therapeutic responses. However, very few studies have evaluated the in-practice current clinical contributions of PET and put it into perspective with classic clinical radiological data.