What Is the Role of Dopamine Transporter Imaging in Parkinson Prevention Clinical Trials?

Recent advances in the understanding of the natural course of brain pathophysiology in the major neurodegenerative disorders including Alzheimer disease and Parkinson disease (PD) have led to therapeutic approaches targeting abnormal brain protein deposition. In PD in particular, there is a need for reliable biomarkers to assess and quantify the clinical consequences of this pathology and support clinical evaluation of the efficacy of new therapeutic strategies. Some clinical measures tracked longitudinally can provide evidence for the efficacy of the therapeutic intervention. These include both motor and non-motor assessments like the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDSUPDRS), quality of life measures, and attaining clinical milestones (e.g., need for medication, onset of falling). Unfortunately, these measures were not developed for tracking the slow rate of clinical change and its high variability between PD patients, nor the resulting difficulty in measuring a reduction in the rate of change of these outcomes. Furthermore, many current trials seek eligibility determinations for trial enrollment in early disease, especially in identifying premotor PD and at-risk individuals for whom, theoretically, the treatment may delay or even prevent the onset of some clinical manifestations of early PD.1,2 In this context, CSF, blood and tissue biomarkers, genomics, and imaging have all been proposed as potential tools to aid in clinical trial eligibility determinations, as well as monitoring the natural course of illness and measuring the efficacy of treatment on slowing disease progression.3,4 Imaging is of value in providing a phenotypic snapshot in living human brain of specific pathologic processes that would otherwise only be obtainable at postmortem.5,6