Asymptomatic Prostate Cancer Brain Metastases on 68Ga-PSMA PET/CT

A Hangover Under 177 Lu-PSMA-617 Therapy : A Red Flag for Brain 68 Ga-PSMA-11 PET/MRI?

ABSTRACT

Leptomeningeal carcinomatosis in prostate cancer is extremely rare. Because of the low overall penetration of drugs into the brain and the prolonged survival of castration-resistant prostate cancer (CRPC) patients, a special attention should be paid to the appearance of neurological symptoms in long-term CRPC survivors. A patient suffering from a CRPC with bone metastases underwent 4 cycles of 177 Lu-PSMA (prostate-specific membrane antigen)-617. Starting from the third cycle, he reported an increasing feeling of a permanent hangover. A 68 Ga-PSMA-11 brain PET/MRI was carried out after the fourth cycle. It revealed intraparenchymatous brain metastases with intense uptake and evidences of leptomeningeal carcinomatosis.

Brain metastasis: An insight into novel molecular targets for theranostic approaches

Brain metastases (BrM) are common malignant lesions in the central nervous system, and pose a significant threat in advanced-stage malignancies due to delayed diagnosis and limited therapeutic options. Their distinct genomic profiles underscore the need for molecular profiling to tailor effective treatments. Recent advances in cancer biology have uncovered molecular drivers underlying tumor initiation, progression, and metastasis. This, coupled with the advances in molecular imaging technology and radiotracer synthesis, has paved the way for the development of innovative radiopharmaceuticals with enhanced specificity and affinity for BrM specific targets. Despite the challenges posed by the blood-brain barrier to effective drug delivery, several radiolabeled compounds have shown promise in detecting and targeting BrM. This manuscript provides an overview of the recent advances in molecular biomarkers used in nuclear imaging and targeted radionuclide therapy in both clinical and preclinical settings. Additionally, it explores potential theranostic applications addressing the unique challenges posed by BrM.

Prostate-specific membrane antigen-based imaging for stereotactic irradiation of low-volume progressive prostate cancer: a single-center experience

Introduction

Prostate-specific membrane antigen (PSMA) is a transmembrane protein that may be expressed on the surface of prostate cancer (PC) cells. It enables a more sensitive and specific diagnosis PC, compared to conventional anatomical imaging.

Aim

The integration of PSMA-based imaging in the personalized radiotherapy of PC patients and the evaluation of its impact on target volume definition if stereotactic body radiotherapy (SBRT) is planned for locally recurrent or oligometastatic disease.

Patients and methods

The data from 363 examinations were analyzed retrospectively. Inclusion criteria were histologically verified PC and clinical data suggesting local recurrence or distant metastasis. Whole-body 99mTc-PSMA-I&S single-photon emission computed tomography (SPECT)/CT or 18F-JK-PSMA-7 positron emission tomography/computer tomography (PET/CT) was carried out, and the evaluation of the scans and biological tumor volume contouring was performed at the Department of Nuclear Medicine. The target volume delineation on topometric CT (TCT) scan was performed at the Department of Oncotherapy. The comparison of the two volumes was performed by image fusion and registration.

Results

From 363 PSMA isotope-based examinations, 84 lesions of 64 patients were treated with SBRT. In 50 patients, 70 lesions were examined for intermodality comparison. The target volume defined by the PSMA density was significantly smaller than the tumor size defined by the TCT scan: GTVCT (gross tumor volume on the TCT), 27.58 ± 46.07 cm3; BTVPSMA (biological target volume on the PSMA-based examination), 16.14 ± 29.87 cm3. During geometrical analyses, the Dice similarity coefficient (DSC) was 0.56 ± 0.20 (0.07-0.85). Prostate-specific antigen (PSA) control was performed to evaluate the response: mean pre-radiotherapy (pre-RT) PSA was 16.98 ng/ml ( ± SD: 33.81), and post-RT PSA at 3 months after SBRT was 11.19 ng/ml ( ± SD: 32.85). Three-month post-therapy PSMA-based imaging was performed in 14 cases, in which we observed a decrease or cessation of isotope uptake. Conventional imaging control was performed in 42 cases (65.6% of all cases): 22 (52.4%) complete remissions, 14 (33.3%) partial remissions, four (9.5%) stable diseases, and two (4.8%) progressive diseases were described.

Conclusion

PSMA-based imaging is a promising diagnostic method for specifying the stage and detecting the low-volume progression. Our results suggest that PSMA-based hybrid imaging can influence treatment decisions and target volume delineation for SBRT.

Identification of incidental brain tumors in prostate cancer patients via PSMA PET/CT

PURPOSE

Brain metastases are rare in patients with prostate cancer and portend poor outcome. Prostate-specific membrane antigen positron emission tomography (PSMA PET)/CT scans including the brain have identified incidental tumors. We sought to identify the incidental brain tumor detection rate of PSMA PET/CT performed at initial diagnosis or in the setting of biochemical recurrence.

METHODS

An institutional database was queried for patients who underwent 68Ga-PSMA-11 or 18F-DCFPyL (18F-piflufolastat) PET/CT imaging at an NCI-designated Comprehensive Cancer Center from 1/2018 to 12/2022. Imaging reports and clinical courses were reviewed to identify brain lesions and describe clinical and pathologic features.

RESULTS

Two-thousand seven hundred and sixty-three patients underwent 3363 PSMA PET/CT scans in the absence of neurologic symptoms. Forty-four brain lesions were identified, including 33 PSMA-avid lesions: 10 intraparenchymal metastases (30%), 4 dural-based metastases (12%), 16 meningiomas (48%), 2 pituitary macroadenomas (6%), and 1 epidermal inclusion cyst (3%) (incidences of 0.36, 0.14, 0.58, 0.07, and 0.04%). The mean parenchymal metastasis diameter and mean SUVmax were 1.99 cm (95%CI:1.25-2.73) and 4.49 (95%CI:2.41-6.57), respectively. At the time of parenchymal brain metastasis detection, 57% of patients had no concurrent extracranial disease, 14% had localized prostate disease only, and 29% had extracranial metastases. Seven of 8 patients with parenchymal brain metastases remain alive at a median 8.8 months follow-up.

CONCLUSION

Prostate cancer brain metastases are rare, especially in the absence of widespread metastatic disease. Nevertheless, incidentally detected brain foci of PSMA uptake may represent previously unknown prostate cancer metastases, even in small lesions and in the absence of systemic disease.

68Ga-PSMA Uptake in Brain Metastasis of Gastric Carcinoma

ABSTRACT

A 69-year-old man with a known history of gastric and prostate adenocarcinoma was referred to 68Ga-prostate-specific membrane antigen (PSMA) PET/CT for restaging due to biochemical recurrence of prostate cancer. 68Ga-PSMA PET/CT revealed tracer accumulation in the primary prostatic lesion, lymph node, bone metastases, and brain lesion, which was later confirmed on biopsy to be metastasis of gastric carcinoma. This case reminds us of the variable spectrum of 68Ga-PSMA uptake in prostatic and nonprostatic metastatic lesions, the potential pitfalls on PET/CT images in the workup of patients with concomitant malignancies.

Prostate-Specific Membrane Antigen as Target for Neuroimaging of Central Nervous System Tumors

Introduction. Positron emission tomography (PET) imaging with prostate-specific membrane antigen- (PSMA-) binding tracers has been found incidentally to demonstrate uptake in CNS tumors. Following the encouraging findings of several such case reports, there is a growing interest in the potential application of PSMA-targeted PET imaging for diagnostics, theranostics, and monitoring of CNS tumors. This is a systematic literature review on PSMA-binding tracers in CNS tumors. Methods. A PubMed search was conducted, including preclinical and clinical reports. One hundred and twelve records were identified, and after screening, 56 were included in the final report. Results. Tissue studies demonstrated PSMA expression in tumor vascular endothelial cells, without expression in normal brain tissue, though the extent and intensity of staining varied by anti-PSMA antibody and methodology. Most included studies reported on gliomas, which showed strong PSMA ligand uptake and more favorable tumor to background ratios than other PET tracers. There are also case reports demonstrating PSMA ligand uptake in prostate cancer brain metastases, nonprostate cancer brain metastases, and meningiomas. We also review the properties of the various PSMA-binding radiotracers available. Therapeutic and theranostic applications of PSMA-binding tracers have been studied, including labeled alpha- and beta-ray emitting isotopes, as well as PSMA targeting in directing MRI-guided focused ultrasound. Conclusions. There is a potential application for PSMA-targeted PET in neuro-oncology as a combination of diagnostic and therapeutic use, as a theranostic modality for managing CNS tumors. Further research is needed regarding the mechanism(s) of PSMA expression in CNS tumors and its differential performance by tumor type.

What to Trust, PSA or [68Ga]Ga-PSMA-11: Learn from Experience

Brain metastases from prostate cancer typically occur in the more advanced stages of the disease. Clinically, the early diagnosis of visceral disease is crucial, impacting on patient’s management and prognosis. Although magnetic resonance imaging (MRI) is the modality of choice for the detection of brain metastases, it is not routinely performed in the surveillance of prostate cancer patients unless neurological manifestations appear. Prostate-specific membrane antigen (PSMA) is a glycoprotein, a membrane-bound metallopeptidase, overexpressed in more than 90% of prostate cancer cells. This molecular target is a suitable tissue biomarker for prostate cancer functional imaging. We present a case of a 73-year gentleman diagnosed with prostate adenocarcinoma and surgically treated (pT3bN1Mx, Gleason Score of 9) in February 2016. Subsequently, he underwent androgen deprivation therapy because of the occurrence of a bone metastasis. Between 2016 and January 2019 PSA levels were maintained under control. Starting from September 2019, it progressively raised up to 0.85 ng/mL with a doubling time of 3.3 months. Therefore, he performed a [⁶⁸Ga]Ga-PSMA-11 PET/CT which showed a focal radiopharmaceutical uptake in the right temporal lobe corresponding to the presence of a rounded cystic lesion on brain MRI. The subsequent excisional biopsy diagnosed a prostate adenocarcinoma metastasis. PSMA expression has been reported in brain parenchyma after ischemic strokes and in some brain tumors including gliomas, meningiomas, and neurofibromas. In our case, the lack of symptoms and the relatively low PSA level raised questions about the nature of the lesion, posing the differential diagnosis between brain metastases and primary brain tumor. Finally, our case shows the capability of [⁶⁸Ga]Ga-PSMA-11 PET/CT to detect metachronous distant brain metastases in a low biochemical recurrent asymptomatic prostate cancer patient, indicating that proper acquisition – from the vertex to thigh – should be always considered, regardless of the PSA level.

Oligodendroglioma in 68Ga-PSMA-11 and 18F-Fluciclovine PET/CT

ABSTRACT

Prostate cancer (PC) is one of the most common cancers affecting men worldwide, with a high recurrence rate after therapy. 68Ga-PSMA-11 and 18F-fluciclovine are PET imaging tracers for the detection of recurrence sites in PC patients. 68Ga-PSMA-11 is a membrane antigen overexpressed by tumor cells, whereas 18F-fluciclovine targets increased amino acid transporter in the membrane of cancer cells. We report a case of an 83-year-old man with known oligodendroglioma and biochemically recurrent PC who shows a high focal 68Ga-PSMA-11 and 18F-fluciclovine uptake in the brain.

68Ga-Prostate-Specific Membrane Antigen PET/CT Uptake in Intraventricular Meningioma in the Choroid Plexus

A 68-year-old man in whom a prostate cancer biochemical recurrence was being investigated was referred for a full-body Ga-prostate-specific membrane antigen PET/CT. Focal uptake in a lesion on the choroid plexus projection was detected. Patient had no neurological complaints. A previous MRI performed 4 years ago showed the same lesion. According to the location and radiological and clinical characteristics, the diagnosis of meningioma was defined. The interpretation of prostate-specific membrane antigen PET/CT must take into account the low frequency of metastases in sites such as the central nervous system, and the possibility of intense uptake in lesions unrelated to prostate cancer.

Neurologically asymptomatic cerebral oligometastatic prostate carcinoma metastasis identified on [Ga]Ga-THP-PSMA PET/CT

Background

Brain metastases from prostate cancer are rare and usually only occur in the context of widespread systemic disease. This is the first case report of a solitary brain oligometastasis, in a neurologically intact prostate cancer patient with no other systemic disease, detected using [⁶⁸Ga]Ga-THP-PSMA PET/CT and only the second one using a PSMA-based radiopharmaceutical.

Case presentation

We report the case of a prostate cancer patient presenting 5 years after robot-assisted laparoscopic prostatectomy with biochemical recurrence, no neurological symptoms, and in the absence of metastatic lesions in the body on conventional imaging. A solitary cerebral metastasis was detected using [⁶⁸Ga]Ga-THP-PSMA PET/CT, surgically resected, leading to a drop in serum PSA and a good recovery.

Conclusion

In this case, [⁶⁸Ga]Ga-THP-PSMA PET/CT resulted in a major change in clinical management and avoided additional morbidity associated with delayed diagnosis and treatment. This report demonstrates the importance of considering the presence of metastatic disease outside the conventional locations of prostate cancer spread, as well as the importance of ensuring comprehensive [⁶⁸Ga]Ga-PSMA PET/CT coverage from vertex to upper thighs.

Prostate Cancer Central Nervous System Metastasis in a Contemporary Cohort

INTRODUCTION

Central nervous system (CNS) metastasis from prostate cancer (PCA) is a rare event, but one with significant prognostic impact for those affected. There are limited data on its impact in contemporary cohorts treated with modern agents.

PATIENTS AND METHODS

A retrospective institutional review was performed to characterize the occurrence/outcome of PCA CNS metastasis on all cases of PCA from 2011 to 2017. A manual chart review was performed to confirm PCA CNS metastases in all cases identified through a diagnostic code screening of the health data.

RESULTS

A total of 6596 cases of PCA were identified, with 29 (20 dural and 9 intraparenchymal) confirmed cases of CNS metastases from PCA. The median survival from the time of diagnosis of CNS metastasis was 2.6 months (95% confidence interval, 2.04-10.78 months) and 5.41 months (95% confidence interval, 3.03 months to not reached) for dural and parenchymal metastases, respectively. Among those who developed CNS metastases, approximately 79% of patients had prior exposure to abiraterone and/or enzalutamide, of whom 50% had ≥ 6 months of exposure. Four (0.07%) of the 5841 patients developed CNS metastases prior to the initiation of therapy or on androgen deprivation therapy alone. In contrast, 24 (8.6%) of the 279 patients with 2 or more lines of medical therapy developed CNS metastases.

CONCLUSIONS

Our analysis highlights the continued poor prognosis of parenchymal and dural CNS metastases from PCA. CNS metastases in PCA remain a rare event with a 0.4% incidence in this series, but this incidence is considerably increased in patients who receive medical therapy beyond first-line androgen deprivation therapy.

Chimeric cytokine receptor enhancing PSMA-CAR-T cell-mediated prostate cancer regression

Objective: Chimeric antigen receptor T (CAR-T) cell therapy has demonstrated an unprecedented therapeutic efficacy in hematological malignancies; however, its effectiveness in solid tumors remains elusive. In order to enable CAR-T cells more effective to solid tumors, a inverted chimeric cytokine receptor (ICR) was designed, which is consists of the TGF-β extracellular domain, IL-7 receptor intracellular domain, and co-expression on CAR-T cells.Materials and Methods: We selected prostate specific membrane antigen (PSMA) as a target for CAR-T cells, constructed corresponding effector cells, and verified the anti-tumor activity of this enhanced PSMA-CAR-T cell by a series of repeated target cell stimulation experiments in vitro and the anti-tumor capabilities by using mice xenograft model in vivo.Results: In vitro experiments showed that co-expression of ICR could significantly enhance sustained anti-tumor capabilities of PSMA-CAR-T cells. Moreover, in vivo experiments also confirmed that the enhanced PSMA-CAR-T cells exhibited significant superior anti-tumor capabilities and could prolong the survival time in the xenograft and PDX models of prostate cancer.Conclusions: PSMA-CAR-T cells co-expressing ICR can be envisaged as a new therapeutic strategy for prostate cancer and support the translation of this enhanced approach in the clinical setting.

68Ga-Prostate-Specific Membrane Antigen Uptake in Cerebral Tuberculosis

A 71-year-old man with a history of high-risk prostate adenocarcinoma (Gleason score 4 + 5 = 9) treated with brachytherapy in 2016 was referred for a Ga-prostate-specific membrane antigen (PSMA)-HBED-CC PET/CT scan for suspected cancer recurrence on a background of slowly rising serum prostate-specific antigen (0.95 ng/mL; reference, <0.2 ng/mL). This revealed PSMA-avid dura-based hyperdense lesions in the brain, suggestive of cerebral metastases. Biopsy demonstrated the presence of acid-fast bacilli, and with further clinical and microbiological testing, a diagnosis of PSMA-avid cerebral tuberculous mycobacterium infection was made.

68Ga-Prostate-Specific Membrane Antigen PET/CT Findings in Extra-axial Metastasis From Prostate Carcinoma

A 67-year-old man with no previous history of malignancy presented with trigeminal neuralgia. MRI of the brain revealed extra-axial lesion along right trigeminal nerve suggestive of neuroma. On histopathology, the lesion was found to be metastasis from adenocarcinoma prostate. Patient underwent Ga-prostate-specific membrane antigen PET/CT for assessing the whole-body status of the disease, which revealed primary prostate lesion, metastatic bone lesions, and extra-axial lesion along the right trigeminal nerve. Extra-axial, intracranial metastasis from prostate carcinoma is an uncommon phenomenon. We describe Ga-prostate-specific membrane antigen PET/CT findings in an exceedingly rare case of extra-axial metastatic lesion from prostate carcinoma.

Beyond the Barrier: Targeted Radionuclide Therapy in Brain Tumors and Metastases

Brain tumors are notoriously difficult to treat. The blood-brain barrier provides a sanctuary site where residual and metastatic cancer cells can evade most therapeutic modalities. The delicate nature of the brain further complicates the decision of eliminating as much tumorous tissue as possible while protecting healthy tissue. Despite recent advances in immunotherapy, radiotherapy and systemic treatments, prognosis of newly diagnosed patients remains dismal, and recurrence is still a universal problem. Several strategies are now under preclinical and clinical investigation to optimize delivery and maximize the cytotoxic potential of pharmaceuticals with regards to brain tumors. This review provides an overview of targeted radionuclide therapy approaches for the treatment of primary brain tumors and brain metastases, with an emphasis on biological targeting moieties that specifically target key biomarkers involved in cancer development.