A comparison of treatment thresholds in two large Parkinson's disease clinical trial cohorts.

Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) and Parkinson Research Examination of CEP-1347 Trial (PRECEPT) were two clinical trials of potential disease-modifying agents for Parkinson's disease that used the time to reaching disability sufficient to require dopaminergic therapy as the primary endpoint. To compare the thresholds for initiating dopaminergic treatment for Parkinson's disease between the two studies, conducted fifteen years apart. Baseline and 12-month endpoint characteristics for subjects in the placebo arms of the two studies were compared. DATATOP placebo subjects had slightly higher total Unified Parkinson's Disease Rating Scale (UPDRS) scores at baseline than PRECEPT placebo subjects (26.1 vs. 23.6, P = 0.03). Time to endpoint was not significantly different. Mean total UPDRS scores at endpoint among those subjects reaching endpoint by 12 months were 48.4 in DATATOP and 37.5 in PRECEPT (P < 0.0001). Baseline disease severity and time to disability requiring dopaminergic therapy were similar in the DATATOP and PRECEPT trials. The threshold for starting dopaminergic treatment was lower in PRECEPT than in the earlier DATATOP study. This may relate to changes in philosophies with respect to starting treatment for Parkinson's disease, but the factors underlying this change remain to be elucidated.