Feasibility of 177Lu Therapy Monitoring Using Fast Whole-Body SPECT Recordings Provided by a High-Speed 360° CZT Camera

Semi-automated segmentation methods of SSTR PET for dosimetry prediction in refractory meningioma patients treated by SSTR-targeted peptide receptor radionuclide therapy

OBJECTIVES

Tumor dosimetry with somatostatin receptor-targeted peptide receptor radionuclide therapy (SSTR-targeted PRRT) by 177Lu-DOTATATE may contribute to improved treatment monitoring of refractory meningioma. Accurate dosimetry requires reliable and reproducible pretherapeutic PET tumor segmentation which is not currently available. This study aims to propose semi-automated segmentation methods to determine metabolic tumor volume with pretherapeutic 68Ga-DOTATOC PET and evaluate SUVmean-derived values as predictive factors for tumor-absorbed dose.

METHODS

Thirty-nine meningioma lesions from twenty patients were analyzed. The ground truth PET and SPECT volumes (VolGT-PET and VolGT-SPECT) were computed from manual segmentations by five experienced nuclear physicians. SUV-related indexes were extracted from VolGT-PET and the semi-automated PET volumes providing the best Dice index with VolGT-PET (Volopt) across several methods: SUV absolute-value (2.3)-threshold, adaptative methods (Jentzen, Otsu, Contrast-based method), advanced gradient-based technique, and multiple relative thresholds (% of tumor SUVmax, hypophysis SUVmean, and meninges SUVpeak) with optimal threshold optimized. Tumor-absorbed doses were obtained from the VolGT-SPECT, corrected for partial volume effect, performed on a 360° whole-body CZT-camera at 24, 96, and 168 h after administration of 177Lu-DOTATATE.

RESULTS

Volopt was obtained from 1.7-fold meninges SUVpeak (Dice index 0.85 ± 0.07). SUVmean and total lesion uptake (SUVmeanxlesion volume) showed better correlations with tumor-absorbed doses than SUVmax when determined with the VolGT (respective Pearson correlation coefficients of 0.78, 0.67, and 0.56) or Volopt (0.64, 0.66, and 0.56).

CONCLUSION

Accurate definition of pretherapeutic PET volumes is justified since SUVmean-derived values provide the best tumor-absorbed dose predictions in refractory meningioma patients treated by 177Lu-DOTATATE. This study provides a semi-automated segmentation method of pretherapeutic 68Ga-DOTATOC PET volumes to achieve good reproducibility between physicians.

CLINICAL RELEVANCE STATEMENT

SUVmean-derived values from pretherapeutic 68Ga-DOTATOC PET are predictive of tumor-absorbed doses in refractory meningiomas treated by 177Lu-DOTATATE, justifying to accurately define pretherapeutic PET volumes. This study provides a semi-automated segmentation of 68Ga-DOTATOC PET images easily applicable in routine.

KEY POINTS

• SUVmean-derived values from pretherapeutic 68Ga-DOTATOC PET images provide the best predictive factors of tumor-absorbed doses related to 177Lu-DOTATATE PRRT in refractory meningioma. • A 1.7-fold meninges SUVpeak segmentation method used to determine metabolic tumor volume on pretherapeutic 68Ga-DOTATOC PET images of refractory meningioma treated by 177Lu-DOTATATE is as efficient as the currently routine manual segmentation method and limits inter- and intra-observer variabilities. • This semi-automated method for segmentation of refractory meningioma is easily applicable to routine practice and transferrable across PET centers.

177Lu-PSMA Treatment Monitoring Through Serial Fast Whole-Body Tomoscintigraphies Recorded With a Latest-Generation CZT-Camera

ABSTRACT

The tomoscintigraphy monitoring of 177Lu-prostate-specific membrane antigen (PSMA) treatment may be helpful for quality control and predicting therapeutic response. Furthermore, the drawbacks of relatively low image quality and extended recording times can be overcome by new CZT-cameras providing fast, high-quality, whole-body recordings. Although still requiring further larger-scale confirmation, the current case report demonstrates that these CZT-cameras have the potential to provide straightforward and comprehensive 177Lu-PSMA treatment monitoring, that is, <20-minute whole-body tomoscintigraphy recording, tumor activities concordant with those from 68Ga-PSMA PET, and no requirement for any additional tracer injection.

Targeted therapy monitoring of BRAF-V600-mutant Erdheim-Chester disease by fast quantitative whole-body bone CZT-tomoscintigraphies

Erdheim-Chester disease (ECD) is a rare histiocytosis due to proto-oncogene mutations, primarily affecting the long bones and possibly being treated by novel targeted therapies. ¹⁸F-FDG PET is a reference technique for ECD assessment. However, we present a case where easier and more objective monitoring of the ECD-related bone metabolism abnormalities under treatment was obtained with the standardized uptake value-based information provided by fast whole-body [Tc-99 m]-HDP bone tomoscintigraphies (QWBT) recorded with a high-sensitivity CZT-camera/computed tomography (CT) hybrid system.

Claudin and pancreatic cancer

Due to the lack of timely and accurate screening modalities and treatments, most pancreatic cancer (PCa) patients undergo fatal PCa progression within a short period since diagnosis. The claudin(CLDN) family is expressed specifically as tight junction structure in a variety of tumors, including PCa, and affects tumor progression by changing the cell junctions. Thus far, many of the 27 members of the claudin family, including claudin-18.2 and claudin-4, have significantly aberrantly expression in pancreatic tumors. In addition, some studies have confirmed the role of some claudin proteins in the diagnosis and treatment of pancreatic tumors. By targeting different targets of claudin protein and combining chemotherapy, further enhance tumor cell necrosis and inhibit tumor invasion and metastasis. Claudins can either promote or inhibit the development of pancreatic cancer, which indicates that the diagnosis and treatment of different kinds of claudins require to consider different biological characteristics. This literature summarizes the functional characteristics and clinical applications of various claudin proteins in Pca cells, with a focus on claudin-18.2 and claudin-4.

Multiparametric 18F-FDG and 68GA-DOTATOC PET Imaging in Bone Metastatic Meningioma Before Radionuclide Therapy: Assessment of Tumor Heterogeneity

ABSTRACT

This report presents the case of a 61-year-old woman with assessment of fronto-temporo-sphenoidal refractory meningioma before radionuclide therapy with pretherapeutic 68Ga-DOTATOC PET/CT. Given the discovery of osteolytic lesions, 18F-FDG PET/CT is planned to search for the primitive origin. Meningioma bone metastasis is confirmed with spine biopsies. The presence of dedifferentiated meningioma lesions indicating that high somatostatin receptor expression does not necessarily coincide with areas of increased glucose metabolism. 18F-FDG and 68Ga-DOTATOC PET/CT allows optimal characterization of tumor heterogeneity and guide targeted therapeutic management before PPRT.

Novel theranostic agent for PET imaging and targeted radiopharmaceutical therapy of tumour-infiltrating immune cells in glioma

BACKGROUND

Malignant gliomas are deadly tumours with few therapeutic options. Although immunotherapy may be a promising therapeutic strategy for treating gliomas, a significant barrier is the CD11b+ tumour-associated myeloid cells (TAMCs), a heterogeneous glioma infiltrate comprising up to 40% of a glioma's cellular mass that inhibits anti-tumour T-cell function and promotes tumour progression. A theranostic approach uses a single molecule for targeted radiopharmaceutical therapy (TRT) and diagnostic imaging; however, there are few reports of theranostics targeting the tumour microenvironment.

METHODS

Utilizing a newly developed bifunctional chelator, Lumi804, an anti-CD11b antibody (αCD11b) was readily labelled with either Zr-89 or Lu-177, yielding functional radiolabelled conjugates for PET, SPECT, and TRT.

FINDINGS

89Zr/177Lu-labeled Lumi804-αCD11b enabled non-invasive imaging of TAMCs in murine gliomas. Additionally, 177Lu-Lumi804-αCD11b treatment reduced TAMC populations in the spleen and tumour and improved the efficacy of checkpoint immunotherapy.

INTERPRETATION

89Zr- and 177Lu-labeled Lumi804-αCD11b may be a promising theranostic pair for monitoring and reducing TAMCs in gliomas to improve immunotherapy responses.

FUNDING

A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.