1. Early prediction of tumour response to PRRT. The sequential change of tumour-absorbed doses during treatment with 177Lu-octreotate.
- Author
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Ezziddin S, Reichmann K, Yong-Hing C, Damm M, Risse J, Ahmadzadehfar H, Logvinski T, Guhlke S, Biersack HJ, and Sabet A
- Subjects
- Adult, Aged, Dose-Response Relationship, Radiation, Female, Humans, Male, Middle Aged, Octreotide therapeutic use, Prognosis, Radionuclide Imaging, Radiopharmaceuticals therapeutic use, Radiotherapy Dosage, Reproducibility of Results, Sensitivity and Specificity, Treatment Outcome, Digestive System Neoplasms diagnostic imaging, Digestive System Neoplasms radiotherapy, Early Detection of Cancer methods, Image Interpretation, Computer-Assisted methods, Octreotide analogs & derivatives, Radiometry methods
- Abstract
Unlabelled: [177Lu-DOTA0,Tyr3]-octreotate (177Lu-octreotate) in peptide receptor radionuclide therapy (PRRT) offers direct intra-therapeutic dosimetry. The aim of this study was to compare tumour and non-tumour parameters and assess intra-individual variations., Patients, Methods: Retrospective analysis of 53 consecutive PRRT treatment cycles (mean activity of 7.53 ± 0.46 GBq 177Lu-octreotate, intended four cycles at intervals of 10-14 weeks, standard nephroprotection) in 27 GEP NET patients. Extended planar dosimetry with serial whole-body imaging on selected, non-superimposed tumour and non-tumour regions; liver (LM), bone (BM), and other (OM) metastases. The per-cycle variation was compared with post-treatment response (CT/MRI three months post-treatment, modified SWOG criteria)., Results: Residence time in tumor lesions (133-147 h) exceeded that in kidneys (93 h). Tumour-to-kidney absorbed dose ratios ranged from 14 to 28 (LM, BM, OM). Intra-individual per-cycle dose variation was insignificant for kidneys, but significant for metastases (LM, BM, and OM; p < 0.05). The mean per-cycle decrease of tumour absorbed dose (ΔD/A0[%]) was linked to morphologic response after PRRT. A mean decrease of >20% was predictive of a partial or minor remission in all 11 evaluable patients, while absent significant dose reduction indicated stable or progressive disease in 4/5 patients. The dose decrease was unrelated to volume effects and also observed for BM., Conclusion: Besides confirmation of a favourable tumour-to-kidney parameter relation for 177Lu-octreotate, stepwise intra-lesional comparison seems to imply a prognostic impact of tumor dosimetry: The early per-cycle change ΔD/A0 between treatment cycles may predict the outcome after PRRT. Larger studies are needed to confirm this finding.
- Published
- 2013
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