Optimizing the automated preparation of the experimental 68Ga-DOTATATE radiotracer

J. Leenhardt, I. Bennegueouche, Ph. Garrigue, B. Guillet Radiopharmacie AP-HM, Hôpital Nord, Marseille

The performance of 68Ga-DOTATATE PET/CT in the diagnosis of neuroendocrine tumors is evaluated through two ongoing monocentric clinical studies in our hospital. The preparation of this experimental radiopharmaceutical drug was set up in our radiopharmacy unit and consists in radiolabeling a cold synthetic somatostatin analog (DOTATATE) with the positron-emitting gallium-68 (Ga-68, physical half-life: 68 minutes). Ga-68 is obtained by the elution of a germanium-68 (Ge-68) / Ga-68 generator hosted in the isolator. The whole preparation process occurs within a shielded class-A isolator, with the help of a dedicated, automated, PC-controlled synthesis module. The literature recommends carrying out a prior elution of the generator at least 3 hours before the second elution used for radiolabeling to minimize radionuclidic impurities in the eluate (i.e. Ge-68). Though, an elution on the previous day would save precious time and allow optimizing the patients planning on the day of the scan. For these purposes, we investigated whether a prior elution on the day before affected the radiolabeling yield and the Ge-68 rate in the preparation.

Data from the automated module reports were collected to extract the labeling yields (%). The Ge-68 rates were measured by radiospectroscopy for each labeling. The radiolabelings showed suitable radiochemical purities (≥95%). Both groups’ data (elution the same day or the day before) were subjected to a Mann-Whitney test for both parameters, only values of P<0.05 being considered significant. The study was conducted over 6 months and the age of the generator (resulting in a progressive lessening) was neglected.

The elution on the previous day (n = 12) provided significantly (P=0.033) superior labeling yields to those with elution the same day (n = 13). Furthermore, we did not see any significant difference in Ge-68 rates between both groups (p = 0.253).

These results confirm that the elution on the previous day is not only possible, but also provides better labeling yields. This will allow us to optimize the number of patients included in the clinical trials.

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