Feasibility of Carbidopa Premedication in Pediatric Patients: A Pilot Study

Abstract

Aim:

To verify the potential role and feasibility of carbidopa premedication in pediatric patients undergoing ¹⁸F-DOPA (Fluorine-18 fluorodihydroxyphenylalanine) PET scanning.

Materials and Methods:

For this limited study, 5 patients (M:F=3:2; mean age 4.8 years) with a positive history for neuroblastoma who had been referred to our institution for instrumental monitoring during clinical follow-up were enrolled. In all cases, two consecutive ¹⁸F-DOPA PET scans, the first without carbidopa and the second with carbidopa premedication, were scheduled: patients received 4 MBq/kg of radiotracer and a dose of 2 mg/kg of carbidopa. Dedicated VOIs were drawn on the basal ganglia, pancreas, liver, and renal cortex. These regions were semiquantitatively analyzed at both the first and at the second ¹⁸F-DOPA scan, and mean SUV_max values were compared using the t-test.

Results:

On a visual basis, a clear reduction in the abdominal accumulation of ¹⁸F-DOPA was observed in all cases after carbidopa premedication. This reduction related both to the biliary structures and the excretory system, and was accompanied by a generalized increase in soft tissue uptake. The semiquantitative analysis documented an absolute increase in SUV_max after carbidopa premedication in the basal ganglia (3.4±1.3 vs. 2.1±0.8) and liver parenchyma (2.2±0.5 vs. 1.5±0.5), whereas SUV_max decreased in the renal cortex (1.7±0.8 vs. 3.7±1.0) and the pancreas (2.3±0.6 vs. 3.5±0.5). The changes in SUV_max were statistically significant for the pancreas and liver parenchyma (p=0.022 and 0.045, respectively), but not for the basal ganglia and renal cortex (p=0.143 and 0.15, respectively).

Conclusions:

Carbidopa premedication in the pediatric population appears feasible and seems to influence ¹⁸F-DOPA distribution in the liver and pancreas in a manner similar to that reported in adults. Larger series are however needed to properly define the clinical role of carbidopa premedication in children.