Goetz, Th. I. and Lang, Elmar W. and Prante, O. and Maier, A. and Cordes, M. and Kuwert, T. and Ritt, P. and Schmidkonz, Christian (2020) Three-dimensional Monte Carlo-based voxel-wise tumor dosimetry in patients with neuroendocrine tumors who underwent Lu-177-DOTATOC therapy. ANNALS OF NUCLEAR MEDICINE, 34 (4). pp. 244-253. ISSN 0914-7187, 1864-6433
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Background Patients with advanced neuroendocrine tumors (NETs) of the midgut are suitable candidates for Lu-177-DOTATOC therapy. Integrated SPECT/CT systems have the potential to help improve the accuracy of patient-specific tumor dosimetry. Dose estimations to target organs are generally performed using the Medical Internal Radiation Dose scheme. We present a novel Monte Carlo-based voxel-wise dosimetry approach to determine organ- and tumor-specific total tumor doses (TTD). Methods A cohort of 14 patients with histologically confirmed metastasized NETs of the midgut (11 men, 3 women, 62.3 +/- 11.0 years of age) underwent a total of 39 cycles of Lu-177-DOTATOC therapy (mean 2.8 cycles, SD +/- 1 cycle). After the first cycle of therapy, regions of interest were defined manually on the SPECT/CT images for the kidneys, the spleen, and all 198 tracer-positive tumor lesions in the field of view. Four SPECT images, taken at 4 h, 24 h, 48 h and 72 h after injection of the radiopharmaceutical, were used to determine their effective half-lives in the structures of interest. The absorbed doses were calculated by a three-dimensional dosimetry method based on Monte Carlo simulations. TTD was calculated as the sum of all products of single tumor doses with single tumor volumes divided by the sum of all tumor volumes. Results The average dose values per cycle were 3.41 +/- 1.28 Gy (1.91-6.22 Gy) for the kidneys, 4.40 +/- 2.90 Gy (1.14-11.22 Gy) for the spleen, and 9.70 +/- 8.96 Gy (1.47-39.49 Gy) for all Lu-177-DOTATOC-positive tumor lesions. Low- and intermediate-grade tumors (G 1-2) absorbed a higher TTD compared to high-grade tumors (G 3) (signed-rank test, p = < 0.05). The pre-therapeutic chromogranin A (CgA) value and the TTD correlated significantly (Pearson correlation: = 0.67, p = 0.01). Higher TTD resulted in a significant decrease of CgA after therapy. Conclusion These results suggest that Monte Carlo-based voxel-wise dosimetry is a very promising tool for predicting the absorbed TTD based on histological and clinical parameters.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | RECEPTOR RADIONUCLIDE THERAPY; ENETS CONSENSUS GUIDELINES; CHROMOGRANIN-A; RESPONSE EVALUATION; PROGNOSTIC-FACTORS; TYR(3) OCTREOTATE; PEPTIDE; LU-177; NEOPLASMS; MIDGUT; Monte Carlo simulations; Dosimetry; Lu-177-DOTATOC; Neuroendocrine tumors |
| Subjects: | 500 Science > 570 Life sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Biophysik und physikalische Biochemie > Prof. Dr. Elmar Lang |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 30 Mar 2021 08:20 |
| Last Modified: | 30 Mar 2021 08:20 |
| URI: | https://pred.uni-regensburg.de/id/eprint/45057 |
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