A standardised protocol for the QUEST multi-centre dosimetry study based on site assessment findings

1504 Objectives The QUEST (Quantitative Uptake Evaluation in SIR-Spheres Therapy) study is an investigator based initiative to understand the dose-response relationship in Y-90 radioembolisation treatment of liver cancer. Based on results from the site assessment phase to characterise scanners, a clinical protocol is proposed for image acquisition and analysis in an attempt to standardise the approach to dosimetry in this study. Methods Standard reconstruction parameters for particular vendors and scanners are proposed. All reconstructed Y-90 PET patient studies will be processed at the core laboratory using software package DOSIsoft (Cahcan, France). Following quantification and co-registration, tumours are defined through segmentation of contrast-enhanced CT and baseline FDG PET, before dose map generation from quantitative Y-90 PET data to establish dose volume histograms in lesions of interest and normal liver. Generation of PERCIST and RECIST reports for comparison with absorbed dose statistics will act as the study endpoint together with quality of life changes. Results Based on site assessment findings, all reconstructions employ 3D iterative methods with CT based scatter and attenuation correction, and lesions of diameter below 20mm are excluded. Trial analysis and reporting on DOSIsoft has begun on patient studies acquired at Royal North Shore Hospital using the Siemens mCT with patient studies acquired within 24 hours of treatment as 2x15 min bed positions, with data reconstructed using resolution recovery and time of flight. Conclusions The use of DOSIsoft for dose analysis enforces standard and consistent processing for a large scale multi-centre study such as QUEST. Based on the site assessment phase, all sites included for clinical dose analysis produce comparable quantitative Y-90 PET data, and so comparable dose information to generate statistically significant findings on the dose-response relationship in SIR-Spheres microspheres therapy for liver cancer.