Abstract

BACKGROUND:

90Y-ibritumomab tiuxetan (90Y-Zevalin) is currently approved for radioimmunotherapy of patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma. The radioimmunoconjugate may be administered to the patient only if the radiolabelling yield is higher than 95%.

AIM:

To evaluate different methods of quality control testing for an accurate and rapid determination of radiolabelling yield in the clinical routine.

METHODS:

Five beta-counting systems, involved in determining the yield of radiolabelled 90Y-Zevalin, were compared: an autoradiography system (AS), a thin-layer chromatography (TLC) scanner system, a dose calibrator (DC), a liquid scintillation analyser (LSA) and high-performance liquid chromatography (HPLC). These instruments were also analysed in terms of efficiency, spatial resolution, analysis time, operating procedure level, cost and availability.

RESULTS:

Radiolabelling yields were comparable among all instruments except for DC whose values were dubious. Efficiency was 1.5+/-0.11 MDLU.s for the AS (where DLU means digital light unit), 3.5+/-0.2 kcps for the TLC analyser, 0.74+/-0.02 MBq for the DC, 15+/-0.12 kcps for LSA and 180+/-0.07 kcps for HPLC. Spatial resolution was 1 mm for AS and 5 mm for the TLC analyser. The quality control test needed 8 min with AS and DC, 15 min with TLC and LSA, and 50 min with HPLC.

CONCLUSIONS:

The short analysis time, high sensitivity, simultaneous detection of multiple radioactive strips and low cost offered by AS make it a suitable tool for radioactivity analysis and quantification in a radiopharmacy laboratory.