Implementation of DOTATOC-Gallium 68 (68Ga) radiolabelling

Montanard E.1, Lopez S. 1, Carpenet-Guery H.1
1 Department of Nuclear Medecine - Dupuytren Hospital, 2 Avenue Martin Luther King, 87000 Limoges - France

Objective
Radiolabelling of 68Ga-DOTATOC, used in neuroendocrine tumors diagnosis, is based on a complexation between 68Ga and a somatostatin analogue. In addition to radiation protection constraints, it requires special conditions of hygiene, pH and temperature. The aim of this work is to implement the 68Ga-DOTATOC labelling in our department.

Material and methods
Syntheses are performed either manually (to approve the technique) or automatically with the Mini AllinOne® synthesis module (MiniAiO). For each synthesis, preparation parameters are noted and compared to those described in Summary of Product Characteristics (SPC): buffer volume (0.5mL), temperature and heating time (95°C ≤10 minutes) and medical devices used on the MiniAiO. Quality controls (QC) of 68Ga-DOTATOC preparations include visual control of organoleptic characteristics (clear solution), pH (3.2-3.8) and RadioChemical Purity (RCP) determination performed by Thin-Layer Chromatography (TLC) with 2 systems (ITLC-SG papers with ammonium acetate (1M)/methanol (1:1 V/V) as mobile phase in the 1st case, and sodium citrate (0.1M, pH 5) in the 2nd). Analyzed using a radiochromatograph MiniGita®, they allow to assess the radiolabelling yield by the 98Ga-DOTATOC RCP, which must be ≥97%. Total duration, including material preparation, synthesis and QC, is noted. Microbiological controls are carried out for preparations (BacTALERT® bottles) and for surfaces: gloves (blood agar) and inside the shielded workstation (contact agar, standard <1 Colony Forming Unit (CFU)).

Results – Discussion
10 syntheses have been conducted. Buffer volume is on average, 0.57 (±0,04) mL. It can be explained by the valve’s dead volume, placed on the module MiniAiO. Temperatures and heating times are:
* for automatic labelling: 120°C during 2 minutes (to let the oven reaches to 95°C) then 95°C during 7 minutes (n=8)
* for manual labelling: 95°C during 7 minutes (n=2).
9/10 syntheses performed are consistent with the SPC (RCP on average 99.26 (±0.31) %). For the non-compliant synthesis (RCP=6.96%), the tubing used for vacuum and aspiration (available on hospital) was 30cm instead of 15cm used in theory with the MiniAiO sequence: the whole buffer volume could not be injected. Finally, the total duration has been improved with each synthesis: 2 hours for the first and 45min for the last (on average 73.5 min).
10 microbiological controls were performed with preparations and 2 inside the workstation: all were compliant. For the gloves, 7 points were controlled before and after manipulation: 21.43% (n=14) were non compliant (with 1CFU).

Conclusion
This work reveals that this radiolabelling is dependent on technical characteristics but also on the knowledge of material like MiniAiO and the availability of medical devices in hospital. Optimization of this radiolabelling and good hygiene results can enable radiolabelling of other molecules with 68Ga.

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