Tore Bach-Gansmo | Theragnostic Imaging

18F-Fluciclovine PET/CT in Suspected Residual or Recurrent High-Grade Glioma

Thu, 01 Aug 2019 00:00:00 +0000

To retrospectively investigate the uptake of F-fluciclovine on PET/CT in patients with suspected recurrent high-grade glioma (HGG). Twenty-one patients were included. The standard of truth was histopathologic interpretation if available. When histopathology was not available or rebiopsy did not show signs of malignancy, clinical follow-up including MRI and clinical outcome was considered the standard of truth. All 21 patients met the reference standard of either histopathologic proof of HGG recurrence (n = 10) or disease progression clinically and with tumor growth corresponding to the primary tumor sites on follow-up MRI (n = 11). Median time from PET/CT to death was 5 months (range, 1-20 months). Median time from primary diagnosis to death was 14.5 months (range, 6 to >400). Average SUVmax of the lesions was 8.3 ± 5.3 (SD) and 0.34 ± 0.13 for normal brain tissue. Median lesion-to-background ratio was 21.6 (range, 3.1-84.4). In 4 patients, F-fluciclovine PET/CT detected small satellite tumors that had not been reported on MR. The uptake of F-fluciclovine in clinically and/or histopathologically confirmed recurrent HGG is high compared with the uptake reported for other amino acid PET tracers. Because of the high tumor uptake and thus high tracer contrast, small satellite tumors with a diameter below usual reported PET spatial resolution and not reported on MRI were detected in 4 patients. As no patients with confirmed treatment-related changes were included, we cannot as of yet ascertain the ability of F-fluciclovine PET to discriminate between recurrent HGG and treatment-related changes, for example, pseudoprogression and radionecrosis.

Biodistribution and Dosimetry Results from a Phase 1 Trial of Therapy with the Antibody-Radionuclide Conjugate 177Lu-Lilotomab Satetraxetan

Sun, 01 Apr 2018 00:00:00 +0000

¹⁷⁷Lu-lilotomab satetraxetan is a novel antibody-radionuclide conjugate currently in a phase 1/2a first-in-humans dose escalation trial for patients with relapsed CD37-positive indolent non-Hodgkin lymphoma. The aim of this study was to investigate biodistribution and absorbed doses to organs at risk.

Methods: In total, 7 patients treated with ¹⁷⁷Lu-lilotomab satetraxetan were included for dosimetry. Patients were grouped on the basis of 2 different predosing regimens (with and without predosing with 40 mg of lilotomab) and were treated with different levels of activity per body weight (10, 15, and 20 MBq/kg). All patients were pretreated with rituximab. Serial planar and SPECT/CT images were used to determine time-activity curves and patient-specific masses for organs with ¹⁷⁷Lu-lilotomab satetraxetan uptake. Doses were calculated with OLINDA/EXM.

Results: The organs (other than red bone marrow and tumors) with distinct uptake of ¹⁷⁷Lu-lilotomab satetraxetan were the liver, spleen, and kidneys. The highest uptake was found in the spleen, with doses ranging from 1.54 to 3.60 mGy/MBq. The liver received 0.70-1.15 mGy/MBq. The kidneys received the lowest dose of the source organs investigated, 0.16-0.79 mGy/MBq. No statistically significant differences in soft-tissue absorbed doses were found between the two predosing regimens. The whole-body dose ranged from 0.08 to 0.17 mGy/MBq.

Conclusion: The biodistribution study for patients treated with ¹⁷⁷Lu-lilotomab satetraxetan revealed the highest physiologic uptake to be in the liver and spleen (besides the red marrow). For all treatment levels investigated, the absorbed doses were found to be modest when compared with commonly assumed tolerance limits.

Tumor-Absorbed Dose for Non-Hodgkin Lymphoma Patients Treated with the Anti-CD37 Antibody Radionuclide Conjugate 177Lu-Lilotomab Satetraxetan

Sun, 01 Jan 2017 00:00:00 +0000

¹⁷⁷Lu-lilotomab satetraxetan is a novel antibody radionuclide conjugate currently tested in a phase 1/2a first-in-human dosage escalation trial for patients with relapsed CD37+ indolent non-Hodgkin lymphoma. The aim of this work was to develop dosimetric methods and calculate tumor-absorbed radiation doses for patients treated with ¹⁷⁷Lu-lilotomab satetraxetan. Patients were treated at escalating injected activities (10, 15 and 20 MBq/kg) of ¹⁷⁷Lu-lilotomab satetraxetan and with different predosing, with or without 40 mg of unlabeled lilotomab. Eight patients were included for the tumor dosimetry study. Tumor radioactivity concentrations were calculated from SPECT acquisitions at multiple time points, and tumor masses were delineated from corresponding CT scans. Tumor-absorbed doses were then calculated using the OLINDA sphere model. To perform voxel dosimetry, the SPECT/CT data and an in-house-developed MATLAB program were combined to investigate the dose rate homogeneity. Twenty-six tumors in 8 patients were ascribed a mean tumor-absorbed dose. Absorbed doses ranged from 75 to 794 cGy, with a median of 264 cGy across different dosage levels and different predosing. A significant correlation between the dosage level and tumor-absorbed dose was found. Twenty-one tumors were included for voxel dosimetry and parameters describing dose-volume coverage calculated. The investigation of intratumor voxel doses indicates that mean tumor dose is correlated to these parameters. Tumor-absorbed doses for patients treated with ¹⁷⁷Lu-lilotomab satetraxetan are comparable to doses reported for other radioimmunotherapy compounds. Although the intertumor variability was considerable, a correlation between tumor dose and patient dosage level was found. Our results indicate that mean dose may be used as the sole dosimetric parameter on the lesion level.