Page 33 - 89Zr-Immuno-PET:Towards a Clinical Tool to Guide Antibody-based Therapy in Cancer

Dosimetry of immuno-PET with 89Zr-cmAb U36
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Figure 2. Illustration of the difference in visual quality of coronal PET images obtained 1 h after injection of 89Zr-cmAb U36 between A: an average weight patient (58 kg) and B: an obese patient (104 kg).
PET derived bloodpool activity vs sampled blood
Variation in visual image quality also affects the quantitative analysis of the 89Zr- cmAbU36 immuno-PET images in a proportion of patients, as shown in Figure 3. This plot depicts the percentage under- and overestimation of the blood activity as assessed by immuno-PET. To this end, immuno-PET derived activity in the left ventricle of the heart was compared to activity in sampled blood. Patients with a weight lower than 100 kg showed in general a good agreement with manually sampled data (mean deviation 0.2 ± 16.9%). Patients above 100 kg showed an underestimation of activity by immuno-PET, especially for later time images.
Figure 4 shows blood kinetics, either assessed by immuno-PET or by blood sampling, for the whole group of evaluable patients (n=19). For the group of patients as a whole, no statistically significant (P = 0.503) differences were observed between the two methods used for assessment of activity. In addition, the small variances suggest a consistency of the pharmacokinetics in these patients, also for patients who developed a HACA response. Therefore, we decided to use data of all these patients for radiation dose estimations.
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