Association Between Dopamine Transporter Activity in the Striatum on ¹⁸F-FP-CIT PET and Overall Survival of Patients With Parkinsonism

Purpose: To investigate whether the overall survival (OS) of patients with parkinsonism is associated with dopamine transporter activity in the striatum measured by ¹⁸F-N-(3-fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) nortropane positron emission tomography (¹⁸F-FP-CIT PET). Methods: From March 2021 to December 2021, ¹⁸F-FP-CIT PET images from patients with Parkinsonism were retrospectively reviewed. Dopamine transporter activity in each striatal region was automatically measured as striatal binding ratio (BR) from PET DICOM files using AI-based quantification (BTXBrain, v1.1.1). Mortality data were obtained from the National Health Insurance system in South Korea. Independent t test was performed to compare regional BRs between nonsurvivor and survivor groups. OS was then compared between low BR and high BR groups for each brain region using Kaplan-Meier curves and the log-rank test. Both univariate and multivariate Cox regression analyses were conducted to calculate hazard ratios (HRs). Results: The final cohort comprised 125 patients (mean age: 73.1 ± 9.4 y) with a median follow-up period of 37 months (range: 31–41 mo). Twenty-six (20.8%) patients died during the follow-up period. Nonsurvivors showed significantly lower BRs in the dorsal striatum (p = 0.03), caudates (p ≤ 0.001), ventroanterior putamen (p = 0.029), anterior pallidum (p = 0.030), ventral striatum (p = 0.002), and subthalamic nucleus (p = 0.032). Patients with low caudate BR (≤ 1.63) demonstrated poorer OS than those with high caudate BR (> 1.63) (HR: 5.48, 95% CI: 1.27–23.59, p < 0.001). In multivariate analysis, old age (HR: 3.136; 95% CI: 1.356–7.251; p = 0.008) and low caudate BR (HR: 5.360; 95% CI: 2.310–12.438; p < 0.001) were significantly associated with higher mortality. Conclusions: In FP-CIT PET of patients with parkinsonism, the binding ratio of the caudate nucleus rather than that of the putamen can serve as a significant prognostic indicator for overall survival. Dopamine transporter activity of the caudate should receive more attention from a prognostic perspective, both in quantified data and visual analysis.