Abstract
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Objectives Identification of interactions between maximum standardized uptake values (SUVmax) from [Ga68]-DOTATATE PET data and achieved tumor doses after peptide radionuclide receptor therapy (PRRT) in patients with metastasized neuroendocrine tumours (NET).
Methods Data of 15 patients (69 ±7 y/o; 4 female, 12 male) were analyzed retrospectively. Patients with NET of the gastroenteropancreatic (n=12) or bronchial system (n=2) and one patient with paraganglioma, were treated either with [90Y]-DOTATATE (n=10) or [177Lu]-DOTATATE (n=4). Tumor doses were calculated according to the MIRD concept, organ specific S-values were taken from the RADAR-website. A total of 31 tumorlesions were examined. SUVmax was determined from [68Ga]-DOTATATE PET data acquired before and three months after PRRT. Normal distribution of all continuous variables was tested by Kolmogorov-Smirnov statistics; Pearson`s correlation was used to identify significant correlations between tumor radiation doses and SUVmax.
Results There was a significant correlation (r=0,6; p<0,05) between pre-therapeutically measured SUVmax (mean: 18.4 ±10.0; range 5.7 - 59.4) and the achieved tumor doses after PRRT (mean: 42.1 ± 28.6 Gray, range 2 - 67 Gray). Additionally, higher tumor doses correlated significantly with higher decline in SUVmax (Delta-SUVmax) from PET data acquired 3 months after therapy (r=0,6; p<0,03).
Conclusions The pre-therapeutically assessed expression of somatostine receptor expression with [68Ga]-DOTATATE PET data is highly predictive for tumor doses achieved from peptide receptor therapy. A dose-dependent decline of somatostatine receptor expression is measurable. Thus, the calculation of SUVmax offers an estimation of the therapy response.