Article
PSMA PET/MRI and Lu177 PSMA therapy in relapsing malignant glioma
PSMA PET/MRT und Lu177 PSMA-Therapie in Patienten mit rezidivierendem malignem Gliom
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Published: | May 25, 2022 |
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Outline
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Objective: Malignant gliomas (MG) are still associated with an unacceptable poor prognosis. New therapeutic targets and strategies are needed to improve patients' survival while preserving health related quality of life. To date, prostate specific membrane antigen (PSMA) is discussed as a therapeutic target for PSMA-directed radioligand therapy (Lu177-PSMA therapy). With this study we aim to investigate and correlate PSMA expression to PSMA tracer uptake in relapsing MG. Further, we provide data of our first experiences with Lu177-PSMA therapy in three patients with relapsing MG.
Methods: Patients with relapsing MG and no other available treatment options have been subjected to PSMA PET/MRI diagnostics to evaluate eligibility for Lu177-PSMA therapy. Quantitative imaging data has been correlated with histopathologically determined PSMA expression. Common toxicity criteria (CTC-AE v5.0) and nuclear medicine data have been assessed in patients who received Lu177-PSMA therapy.
Results: In total 20 patients with a median age of 53 (IQR 42-57) years and a female-to-male ratio of 1:3 were evaluated with PSMA PET/MRI. Median SUVmean was 3.2 (IQR 2.5-3.9) in the tumor and 4.3 (IQR 3.6-5.7) in the liver. Tumor-to-liver ratio of SUVmean was 0.7 (IQR 0.6-0.9). In three patients, we observed a significant uptake with consecutive tumor-to-liver ratios of 1.2, 1.4 and 1.5 and therefore, those patients have been subjected to Lu177-PSMA therapy. So far, each patient has completed two cycles of therapy. In one patient, CTC AE °2 with a thrombocytopenia of 68 / nl related to the treatment occurred. Histological studies exhibited variable PSMA expression but suggested a correlation of high PSMA expression in the tumor neovasculatur in patients with increased PSMA uptake of the tumor.
Conclusion: With this study, we show that only few (15%) patients with relapsing MG qualified for Lu177-PSMA therapy. However, our preliminary data demonstrated acceptable toxicity. Further, PSMA expression in the neovasculature of MG may correspond with the PSMA uptake. More patients need to be evaluated to prove PSMA staining as a screening tool prior to PSMA PET initiation, and to draw conclusions on toxicity and efficacy of Lu177 PSMA therapy.