Incidental Malignancies Identified During Staging for Prostate Cancer With 68Ga Prostate-specific Membrane Antigen HBED-CC Positron Emission Tomography Imaging

MRI/PET Imaging in elevated PSA and localized prostate cancer: a narrative review

OBJECTIVE

To review the recent milestones in MRI and PET based imaging and evaluate their evolving role in the setting of elevated PSA as well as localized prostate cancer.

BACKGROUND

The importance of multiparametric MRI (mpMRI) and PET based imaging for the diagnosis and staging of prostate cancer cannot be understated. Accurate staging has become another significant milestone with the use of PET scans, particularly with prostate specific radiotracers like 68-Gallium Prostate Specific Membrane Antigen (68Ga-PSMA). Integrated PET/MRI systems are commercially available and can be modulated to evaluate the unique needs of localized as well as recurrent prostate cancer.

METHODS

A literature search was performed using PubMed and Google Scholar using the MeSH compliant and other keywords that included prostate cancer, PSA, mpMRI, PET CT, PET/MRI.

CONCLUSIONS

mpMRI has now established itself as the gold-standard of local prostate imaging and has been incorporated into international guidelines as part of the diagnostic work-up of prostate cancer. PSMA PET/CT has shown superiority over conventional imaging even in staging of localized prostate cancer based on recent randomized control data. Imaging parameters from PET/MRI have been shown to be associated with malignancy, Gleason score and tumour volume. As mpMRI and PSMA PET/CT become more ubiquitous and established; we can anticipate more high-quality data, cost optimization and increasing availability of PET/MRI to be ready for primetime in localized prostate cancer.

PSMA radioligand therapy for solid tumors other than prostate cancer: background, opportunities, challenges, and first clinical reports

In the past decade, a growing body of literature has reported promising results for prostate-specific membrane antigen (PSMA)-targeted radionuclide imaging and therapy in prostate cancer. First clinical studies evaluating the efficacy of [¹⁷⁷Lu]Lu-PSMA radioligand therapy (PSMA-RLT) demonstrated favorable results in prostate cancer patients. [¹⁷⁷Lu]Lu-PSMA is generally well tolerated due to its limited side effects. While PSMA is highly overexpressed in prostate cancer cells, varying degrees of PSMA expression have been reported in other malignancies as well, particularly in the tumor-associated neovasculature. Hence, it is anticipated that PSMA-RLT could be explored for other solid cancers. Here, we describe the current knowledge of PSMA expression in other solid cancers and define a perspective towards broader clinical implementation of PSMA-RLT. This review focuses specifically on salivary gland cancer, glioblastoma, thyroid cancer, renal cell carcinoma, hepatocellular carcinoma, lung cancer, and breast cancer. An overview of the (pre)clinical data on PSMA immunohistochemistry and PSMA PET/CT imaging is provided and summarized. Furthermore, the first clinical reports of non-prostate cancer patients treated with PSMA-RLT are described.

A Review of Prostate-Specific Membrane Antigen (PSMA) Positron Emission Tomography (PET) in Renal Cell Carcinoma (RCC)

Metastatic renal cell carcinoma (mRCC) is a disease that portends poor prognosis despite an increasing number of novel systemic treatment options including new targeted therapies and immunotherapy. Ablative intervention directed at oligometastatic RCC has demonstrated survival benefit. Consequently, developing techniques for improved staging of mRCC on contemporary imaging modalities including X-ray computed tomography (CT), magnetic resonance imaging (MRI) and/or bone scan (BS) is a clinical priority. This is relevant for metastatic deposits too small to characterize or lymph nodes within physiological normality. Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein highly expressed on prostate cancer epithelial cells. Recently, small molecules targeting the PSMA receptor, linked to radioactive isotopes have been developed for use with positron emission tomography (PET). Despite its nomenclature, PSMA has also been found to be expressed in the neovasculature of non-prostate cancers such as renal cell carcinoma (RCC) and hence PSMA PET/CT imaging has been proposed as an alternative staging modality. Preliminary small studies involving the use of PSMA PET/CT imaging in mRCC have been encouraging with evidence of improved staging sensitivity which has directly led to change in management in some cases. Given these early encouraging reports, we performed a comprehensive narrative review on the available evidence, including the scientific basis for PSMA expression in RCC, the role of PSMA PET/CT imaging with potential clinical implications in mRCC, its limitations and future opportunities.

Impact of 68Ga-PSMA PET/CT in the treatment of prostate cancer: Initial experience in Spain

Aim

To evaluate whether positron-emission tomography/computed tomography with ⁶⁸Ga-PSMA (⁶⁸Ga-PSMA PET/CT) influences the therapeutic management of patients with primary or recurrent prostate cancer (PCa).

Background

Although ⁶⁸Ga-PSMA PET/CT is one of the best options for staging or restaging patients with PCa, its availability is still very limited in Spain. The present study reports the results of the first group of patients in Spain who underwent ⁶⁸Ga-PSMA PET/CT imaging.

Materials and methods

All patients (n = 27) with a histological diagnosis of PCa who underwent ⁶⁸Ga-PSMA PET/CT prior to the definitive treatment decision at the only centre with this technology in Spain during 2017-2018 were included. Two nuclear medicine physicians and a radiologist reviewed the imaging studies. The clinical impact was assessed from a theoretical perspective, based on the treatment that would have been applied if no data from the ⁶⁸Ga-PSMA PET/CT were available.

Results

Most patients (n = 26; 96%) had persistent disease or biochemical recurrence after radical prostatectomy, radiotherapy, or combined treatment. One patient underwent ⁶⁸Ga-PSMA PET/CT imaging to stage high-risk PCa. Overall, ⁶⁸Ga-PSMA PET/CT was positive in 19 patients (70.4%). In 68.75% of these patients, none of the other imaging tests-MRI, CT, or bone scans-performed prior to the ⁶⁸Ga-PSMA PET/CT were able to detect the presence of cancerous lesions. Overall, the findings of the ⁶⁸Ga-PSMA PET/CT led to a modification of the therapeutic approach in 62.96% of the patients in the study.

Conclusions

⁶⁸Ga-PSMA PET/CT alters the therapeutic approach in a substantial proportion of patients with PCa.

68Ga-PSMA PET thyroid incidentalomas

INTRODUCTION

Thyroid incidentaloma is defined as a thyroid lesion incidentally and newly detected by imaging techniques performed for an unrelated purpose and especially for a non-thyroid disease. The aim of this review is to evaluate the prevalence and clinical significance of focal incidental radiolabelled prostate-specific membrane antigen (PSMA) uptake in the thyroid gland [PSMA thyroid incidentaloma (PTI)] revealed by PET/CT or PET/MRI.

METHODS

A comprehensive literature search of the PubMed/MEDLINE, Scopus, and Embase databases was conducted to find relevant published articles about the prevalence and clinical significance of PTIs detected by PET/CT or PET/MRI in patients studied for other oncologic purposes.

RESULTS

Twelve articles were included in the systematic review. Among 23 PTIs, 6 were malignant (5 primary thyroid tumors and one metastasis from renal cell carcinoma), one was a follicular lesion of undetermined significance, and the rest were benign.

CONCLUSION

Despite being very rare, though probably underestimated, PTIs frequently signal the presence of unexpected lesions in the thyroid which differ from the indicated reason for which the patient was initially scanned and concerning which the risk of malignancy is not negligible.

The Impact of 68Ga-PSMA PET/CT and PET/MRI on the Management of Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a transmembrane protein with significantly increased expression in the cells and metastases of prostate carcinoma (CaP). PSMA-expression correlates with higher serum levels of prostate-specific antigen (PSA) and a higher Gleason score (GS). This finding has led to the development of novel imaging modalities such as 68Ga-/18F-labeled PSMA positron emission tomography/computed tomography (PET/CT) and positron emission tomography/magnetic resonance imaging (PET/MRI). This article reviews the literature pertaining to various new imaging technologies for the management of CaP. PSMA positron emission tomography/computed tomography appears to be an excellent diagnostic tool, that may drastically impact the management of a large number of patients with primary and recurrent CaP.

Pancreatic Ductal Adenocarcinoma With High Radiotracer Uptake in 68Ga-Prostate-Specific Membrane Antigen PET/CT

Prostate-specific membrane antigen imaging with PET/CT is increasingly used in prostate cancer and was shown to have a high diagnostic performance. We report a clinical case of a 67-year-old man with previous history of operated prostate cancer and increasing prostate-specific antigen blood level. Ga-HBED-CC prostate-specific membrane antigen PET/CT imaging was indicated for the assessment of local recurrence and lymph node metastases of prostate cancer. In addition, a soft tissue mass in the body of the pancreas with high radiotracer uptake was detected. Histopathology confirmed a pancreatic ductal adenocarcinoma.

Pearls and pitfalls in clinical interpretation of prostate-specific membrane antigen (PSMA)-targeted PET imaging

BACKGROUND

The rapidly expanding clinical adaptation of prostate-specific membrane antigen (PSMA)-targeted PET imaging in the evaluation of patients with prostate cancer has placed an increasing onus on understanding both the potential pearls of interpretation as well as limitations of this new technique. As with any new molecular imaging modality, accurate characterization of abnormalities on PSMA-targeted PET imaging can be accomplished only if one is aware of the normal distribution pattern, physiological variants of radiotracer uptake, and potential sources of false-positive and false-negative imaging findings. In recent years, a growing number of reports have come to light describing incidental non-prostatic benign or malignant pathologies with high uptake on PSMA-targeted PET imaging. In this review, we have summarized the published literature regarding the potential pearls and technical and interpretive pitfalls of this imaging modality. Knowledge of these limitations can increase the confidence of interpreting physicians and thus improve patient care.

CONCLUSIONS

As PSMA-targeted PET is expected to be evaluated in larger prospective trials, the dissemination of potential diagnostic pitfalls and the biologic underpinning of those findings will be of increased importance.