Comparison of two radiolabelled molecules used to assess kidney function in children with cancer using IT tools.

The clearances of ^99mTc-DTPA and ⁵¹Cr-EDTA are two reference methods for determining glomerular filtration rate in paediatrics. An original approach to comparing the two molecules based on population pharmacokinetics was used to assess the bias in estimating renal clearance in children depending on the molecule used. A cohort of 40 patients received ⁵¹Cr-EDTA and a cohort of 19 patients received ^99mTc-DTPA. Certain parameters deemed relevant to the comparison were taken into account: serum creatinine, plasma cystatin C and body weight. A very small bias (-0.9%) was observed between the use of ^99mTc-DTPA and ⁵¹Cr-EDTA in estimating patient renal function. These two radioactive molecules are therefore equivalent in paediatrics and can be substituted. In addition, the population pharmacokinetic approach based on a simultaneous analysis of two different molecules and use of a covariate to distinguish them is original and can be applied for comparing other compounds.

This work shows that the two clearances of the molecules ⁵¹Cr-EDTA and ^99mTc-DTPA used to estimate the GFR of paediatric patients are equivalent. A change from one molecule to the other will have no clinical impact on the patient, as the estimate of renal function will be similar.

The use of population pharmacokinetics to compare two different molecules could be extended to other clinical contexts and provide answers to questions such as therapeutic change.

Collaborations and partnerships

Collaborations :

• Unité de Radiopharmacie du CHU de Toulouse (Mathieu Alonso)
• Service d’OncoPédiatrie du CHU de Toulouse (Marlène Pasquier)