Vertebral Hemangioma Mimicking Bone Metastasis in 68Ga—PSMA Ligand PET/CT

PSMA PET/CT imaging and its application to prostate cancer treatment

Recognition of the importance of prostate-specific membrane antigen (PSMA) PET/CT in the diagnosis of prostate cancer has steadily increased following the publication of extensive data on its diagnostic accuracy and impact on patient management over the past decade. Several recent clinical trials and investigations regarding PSMA PET/CT have been ongoing in our country, and this examination is expected to become increasingly widespread in the future. This review explains the characteristics of PSMA PET/CT, its diagnostic capabilities and superiority over other modalities, the three proposed PSMA PET/CT interpretation criteria (the European Association of Nuclear Medicine [EANM], the Prostate Cancer Molecular Imaging Standardized Evaluation [PROMISE], and the PSMA Reporting and Data System [PSMA-RADS]), and the application of PSMA PET/CT to prostate cancer treatment (improvement of local control, irradiation of oligometastases, and salvage radiotherapy), incorporating actual clinical images and the latest findings.

Prostate specific membrane antigen (PSMA) avid nonprostatic benign and malignant disease: a pictorial review

Prostate specific membrane antigen (PSMA) positron emission tomography-computed tomography (PET-CT) is revolutionising the management of prostate cancer (PC) in primary staging and assessment of biochemical recurrence (BCR) through its higher diagnostic accuracy compared to both conventional imaging and previously available PET radiopharmaceuticals. PSMA is a transmembrane glycoprotein, highly expressed in prostate cancer, with its extracellular domain the target for PSMA PET radiopharmaceuticals. However, PSMA expression is not prostate specific and resultant PSMA uptake on PET-CT is not restricted to pathologies arising from the prostate gland. The increasing use of PSMA PET-CT has revealed PSMA uptake in a variety of non-prostatic benign and malignant diseases, which adds complexity to PET-CT interpretation and subsequent clinical management. This pictorial review will provide a thorough knowledge and understanding of the comprehensive range of PSMA avid non-prostatic benign and malignant diseases demonstrable on PSMA PET-CT, whilst highlighting the complimentary nature of other imaging modalities.

Hemangioma of the Ilium Simulating Bone Metastasis on 18 F-PSMA-1007 PET/CT

ABSTRACT

A 64-year-old man was referred for 18 F-PSMA-1007 PET/CT scan for initial staging of biopsy-proved prostate adenocarcinoma. 18 F-PSMA-1007 PET/CT showed focal intense 18 F-PSMA-1007 of the prostate adenocarcinoma and a focal intense activity with SUV max of 10.5 in the left ilium. The 18 F-PSMA-1007-avid iliac bone lesion corresponded to a hemangioma, which was initially detected on pelvic MRI 13 months ago and remained stable in size. This case indicates that hemangioma should be included in the differential diagnosis of PSMA-avid iliac bone lesions.

Incidental Detection of Synchronous Benign Hepatic and Splenic Hemangiomas on 18 F-PSMA PET/CT

ABSTRACT

A 51-year-old man with biochemical failure after brachytherapy for prostatic adenocarcinoma (PSA 5 μg/L rising to 6.45 μg/L) underwent a PSMA PET/CT scan. The scan revealed focal 18 F-PSMA activity at the right apex suggestive of local residual or recurrent disease. In addition, 18 F-PSMA images demonstrated 2 focal 18 F-PSMA-avid liver and spleen lesions; both lesions were further evaluated by abdominal MRI, and the final radiological diagnosis was synchronous hepatic and splenic hemangiomas.

Prostate-specific membrane antigen-positron emission tomography (PSMA-PET) of prostate cancer: current and emerging applications

Prostate-specific membrane antigen-positron emission tomography (PSMA-PET) is transforming the management of patients with prostate cancer. In appropriately selected patients, PSMA-PET offers superior sensitivity and specificity compared to conventional imaging (e.g., computed tomography and bone scintigraphy) as well as choline and fluciclovine PET, with the added benefit of consolidating bone and soft tissue evaluation into a single study. Despite being a newly available imaging tool, PSMA-PET has established indications, interpretation guidelines, and reporting criteria, which will be reviewed. The prostate cancer care team, from imaging specialists to those delivering treatment, should have knowledge of physiologic PSMA radiotracer uptake, patterns of disease spread, and the strengths and limitations of PSMA-PET. In this review, current and emerging applications of PSMA-PET, including appropriateness use criteria as well as image interpretation and pitfalls, will be provided with an emphasis on clinical implications.

Intense 18 F-PSMA-1007 Uptake of Splenic Hemangioma

ABSTRACT

A 77-year-old man was referred for 18 F-PSMA-1007 PET/CT scan for initial staging of biopsy-proved prostate adenocarcinoma. 18 F-PSMA-1007 PET/CT showed focal intense 18 F-PSMA-1007 of the prostate adenocarcinoma and a focal intense activity (SUV max , 27) in the spleen. The 18 F-PSMA-1007-avid splenic lesion corresponded to a splenic hemangioma, which was initially detected on contrast-enhanced CT 7 months ago and unchanged in size and enhancement pattern on follow-up contrast-enhanced CT. This case indicates that splenic hemangioma should be included in the differential diagnosis of PSMA-avid splenic lesions.

Intravenous Pyogenic Granuloma in the Inguinal Canal Mimicking Lymph Node Metastasis on PSMA PET/CT

ABSTRACT

We present a 68-year-old man with newly diagnosed high-risk prostate cancer who was referred for PSMA PET/CT after the initial CT showed a contrast-enhanced structure resembling a lymph node in the left inguinal canal. No other findings suggesting metastatic disease were seen on CT or bone scintigraphy. PSMA PET/CT showed moderate PSMA uptake in the inguinal tissue, substantiating an unexpected location of lymph node metastasis. The uncommon location warranted an excision biopsy, and an IV pyogenic granuloma was diagnosed on histological examination, emphasizing the importance of biopsy of unexpected findings.

Musculoskeletal pitfalls in 68Ga-PSMA PET/CT

Prostate-specific membrane antigen (PSMA) is a transmembrane protein expressed in normal prostate cells and overexpressed in prostate cancer. Consequently, it is an important tool in the evaluation of prostate cancer, including the staging of high-risk patients and the assessment of biochemical recurrence. Despite the "specific" designation, benign musculoskeletal conditions, such as fractures, osteodegenerative changes, and fibrous dysplasia, can also show PSMA uptake, which can lead to misinterpretation of the imaging findings. Therefore, radiologists must be aware of these potential pitfalls, understand their causes, and fully analyze their morphologic features on unfused computed tomography (CT) and magnetic resonance imaging scans to correctly interpret the examination. In this pictorial essay, we review the basic characteristics of the 68Ga-PSMA positron-emission tomography/CT (PET/CT) radiotracer, discuss potential causes of false-positive findings on 68Ga-PSMA PET/CT in the musculoskeletal system, and illustrate the corresponding imaging findings.

Intense PSMA Uptake in a Vertebral Hemangioma Mimicking a Solitary Bone Metastasis in the Primary Staging of Prostate Cancer via 68Ga-PSMA PET/CT

A 78-year-old man with newly diagnosed high-risk prostate cancer underwent ⁶⁸Ga-PSMA PET/CT for primary staging. This showed a single, very intense PSMA uptake in the vertebral body of Th2, without discrete morphological changes on low-dose CT. Thus, the patient was considered oligometastatic and underwent MRI of the spine for stereotactic radiotherapy planning. MRI demonstrated an atypical hemangioma in Th2. A bone algorithm CT scan confirmed the MRI findings. The treatment was changed, and the patient underwent a prostatectomy with no concomitant therapy. At three and six months after the prostatectomy, the patient had an unmeasurable PSA level, confirming the benign etiology of the lesion.

Not All Glittering Bone Lesions Are Gold: A Case of Sclerotic Bone Lesions with Elevated 68 Ga PSMA and 99m Tc HDP Uptake with No Signs of Malignancy

Gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography ( ⁶⁸ Ga PSMA PET/CT) outperforms CT and bone scintigraphy in terms of diagnostic accuracy for the primary staging of prostate cancer and has become widely used. However, ⁶⁸ Ga PSMA uptake is also encountered in nonprostatic tissue. We present a 63-year-old male with newly diagnosed high-risk prostate cancer who underwent bone scintigraphy with single-photon emission computed tomography/computed tomography (SPECT/CT), which showed inhomogeneous elevated uptake in sclerotic bone lesions in the pelvis. Likewise, ⁶⁸ Ga PSMA PET/CT revealed inhomogeneous uptake in the same areas. Subsequent biopsy revealed hyperplastic bone marrow without signs of malignancy. The patient underwent radical prostatectomy, and the prostate-specific antigen level dropped to less than 0.1 ng/mL.

Hybrid Ga-68 prostate-specific membrane antigen PET/MRI in the detection of skeletal metastasis in patients with newly diagnosed prostate cancer: Contribution of each part to the diagnostic performance

PURPOSE

Bone metastasis is essential in patients with prostate cancer (PCa) as it determines prognosis and survival. Hybrid PET/MRI allows simultaneous acquisition of PET and MRI data, thus combining the strength of both technologies allows the detection of bone marrow metastases that are missed by PET/CT. In this retrospective study, we aimed to evaluate the diagnostic efficiency of hybrid PET/MRI with Ga-68 prostate-specific membrane antigen (PSMA) in detecting skeletal metastases in newly diagnosed PCa patients and compared the effectiveness of stand-alone PSMA PET reviewing versus stand-alone whole-body (WB) MRI evaluation. We also investigated the effect of the interpretation of all PET/MR data together on clinical management.

METHODS

We studied 74 newly diagnosed PCa patients who underwent PSMA PET/MRI for staging purposes. At first, PET and MRI were evaluated separately for bone lesions on a patient-and-lesion basis and then a further joint PSMA PET/MRI interpretation was made.

RESULTS

Patient-based sensitivity, specificity, positive predictive value, negative predictive value and accuracy analysis for bone metastasis was, respectively, 1.0, 0.83, 0.54, 1.0, 0.86 for PET; 0.75, 0.96, 0.81, 0.95, 0.93 for WB MRI and 0.91, 0.95, 0.78, 0,98, 0.94 for PET/MRI. The combined PET/MRI evaluation changed the clinical impact in 13.5% of patients (eight correct and two wrong decisions) compared to PET stand-alone interpretation.

CONCLUSION

PSMA PET imaging showed superior sensitivity to WB MRI in detecting bone metastases in newly diagnosed PCa patients, whereas WB MRI has superior specificity and PPV. Furthermore, the specificity and PPV of joint PET/MRI evaluation are better than PSMA PET alone. Despite the longer acquisition period, adding WB MRI sequences to PSMA PET imaging appears beneficial for PCa patient management.

PSMA-1007 Uptake in Ganglia of the Sympathetic Trunk and Its Intra-individual Reproducibility

Aim/Purpose

18F-labeled PSMA ligands offer various advantages as PET tracers over 68Ga-labeled PSMA counterparts. Especially, an improved spatial resolution leads to improved detection rates of smaller prostate cancer (PCa) lesions. However, physiological PSMA uptake of ganglia of the sympathetic trunk can be quickly misinterpreted as possible PSMA-positive lymph node metastases. The aim of this retrospective study is to investigate [18F]PSMA-1007 uptake and its intra-individual reproducibility in ganglia of the sympathetic trunk.

Methods

We retrospectively included 28 consecutive patients (median age 69 ± 9 with a range of 49–90) with biochemical recurrence of PCa who underwent [18F]PSMA-1007 PET/CT scan and, accordingly, a follow-up examination between August 2018 and August 2021. Cervical, coeliac, and sacral ganglia were identified on the iterative PET reconstructions and correlated with CT component. Tracer uptake of ganglia was determined by measuring SUVmax and SUVmean values. Anatomical position of the ganglia in relation to adjacent vertebral bodies were noted. Statistical analyses were conducted using two-way repeated measures ANOVA and descriptive statistics.

Results

The highest [18F]PSMA-1007 uptake was found in coeliac ganglia followed by cervical and sacral ganglia. The SUVmax in coeliac ganglia was 3.13 ± 0.85 (follow-up scan 3.11 ± 0.93), in cervical ganglia 2.73 ± 0.69 (follow-up scan 2.67 ± 0.74), and in sacral ganglia 1.67 ± 0.50 (follow-up scan 1.64 ± 0.52). The SUVmean in coeliac ganglia was 2.28 ± 0.64 (follow-up scan 2.28 ± 0.66), in cervical ganglia 1.62 ± 0.43 (follow-up scan 1.61 ± 0.43) and in sacral ganglia 1.15 ± 0.33 (follow-up scan 1.12 ± 0.34). In a given ganglion station, there was no statistically significant difference of SUVmax or SUVmean values between baseline and follow-up scans.

Conclusions

The first systematically described physiological [18F]PSMA-1007 uptake in ganglia of the sympathetic trunk showed a low variability of SUVmax or SUVmean and a good intra-individual reproducibility of [18F]PSMA-1007 uptake in follow-up scans. These findings might improve and guide the differentiation of ganglia from possible malignant lesions.

Incidental Detection of Radiotracer Uptake in Spindle Cell Lipoma on 18 F-PSMA PET/CT

ABSTRACT

An 84-year-old man underwent 18 F-prostate-specific membrane antigen (PSMA) PET/CT for staging of a newly diagnosed prostate adenocarcinoma. PET/CT revealed high 18 F-PSMA uptake in a thigh mass, which was initially suspected for a metastasis. Histopathology revealed a rare entity of spindle cell lipoma, which should be added to the reported list of neoplasms that can show "false-positive" PSMA uptake during evaluation of patients with prostate carcinoma representing a potential interpretative pitfall.

Multidisciplinary management of spinal metastases: what the radiologist needs to know

The modern management of spinal metastases requires a multidisciplinary approach that includes radiation oncologists, surgeons, medical oncologists, and diagnostic and interventional radiologists. The diagnostic radiologist can play an important role in the multidisciplinary team and help guide assessment of disease and selection of appropriate therapy. The assessment of spine metastases is best performed on MRI, but imaging from other modalities is often needed. We provide a review of the clinical and imaging features that are needed by the multidisciplinary team caring for patients with spine metastases and stress the importance of the spine radiologist taking responsibility for synthesizing imaging features across multiple modalities to provide a report that advances patient care.

PET-CT in Clinical Adult Oncology-IV. Gynecologic and Genitourinary Malignancies

Simple Summary

Positron emission tomography (PET), typically combined with computed tomography (CT), has become a critical advanced imaging technique in oncology. With concurrently acquired positron emission tomography and computed tomography (PET-CT), a radioactive molecule (radiotracer) is injected in the bloodstream and localizes to sites of tumor because of specific cellular features of the tumor that accumulate the targeting radiotracer. The CT scan provides information to allow better visualization of radioactivity from deep or dense structures and to provide detailed anatomic information. PET-CT has a variety of applications in oncology, including staging, therapeutic response assessment, restaging and surveillance. This series of six review articles provides an overview of the value, applications, and imaging interpretive strategies for PET-CT in the more common adult malignancies. The fourth report in this series provides a review of PET-CT imaging in gynecologic and genitourinary malignancies.

Abstract

Concurrently acquired positron emission tomography and computed tomography (PET-CT) is an advanced imaging modality with diverse oncologic applications, including staging, therapeutic assessment, restaging and longitudinal surveillance. This series of six review articles focuses on providing practical information to providers and imaging professionals regarding the best use and interpretative strategies of PET-CT for oncologic indications in adult patients. In this fourth article of the series, the more common gynecological and adult genitourinary malignancies encountered in clinical practice are addressed, with an emphasis on Food and Drug Administration (FDA)-approved and clinically available radiopharmaceuticals. The advent of new FDA-approved radiopharmaceuticals for prostate cancer imaging has revolutionized PET-CT imaging in this important disease, and these are addressed in this report. However, [¹⁸F]F-fluoro-2-deoxy-d-glucose (FDG) remains the mainstay for PET-CT imaging of gynecologic and many other genitourinary malignancies. This information will serve as a guide for the appropriate role of PET-CT in the clinical management of gynecologic and genitourinary cancer patients for health care professionals caring for adult cancer patients. It also addresses the nuances and provides guidance in the accurate interpretation of FDG PET-CT in gynecological and genitourinary malignancies for imaging providers, including radiologists, nuclear medicine physicians and their trainees.

18F DCFPyL PSMA avid biopsy proven subcutaneous capillary haemangioma as a malignancy mimic in the setting of biochemical recurrent prostate carcinoma

We present a case of a 65-year-old male with a biopsy proven subcutaneous capillary haemangioma identified on imaging for evaluation of further metastatic spread of prostatic carcinoma due to a rise in his prostate-specific antigen biochemistry. He was receiving salvage radiation therapy for his known isolated nodal disease, four years after prostatectomy. An intensely avid prostate-specific membrane antigen positron emission tomography-computed tomography lesion in the left paramedian back at the level of L1 was noted on his scan. A core biopsy revealed a dermal haemangioma with no evidence of metastatic prostatic carcinoma. To our knowledge, only one other incidental case of prostate-specific membrane antigen avid subcutaneous capillary haemangioma has been described in the literature. Whilst uncommon, incidental findings of prostate-specific membrane antigen PET avid dermal lesions are pathognomonic for haemangiomas and can be treated as “no touch” lesions with watchful observation.

The differential diagnostic value of dual-phase 18F-DCFPyL PET/CT in prostate carcinoma

OBJECTIVE

Binding of ¹⁸F-DCFPyL at prostate cancer (PC) cells increases over time. The dual-phase protocol may be helpful in separating benign lesions from malignant ones associated with prostate cancer. The purpose of this study was to retrospectively analyze the incremental diagnostic value of ¹⁸F-DCFPyL dual-time imaging in patients with prostate cancer.

METHOD

114 prostate-related malignant lesions and 43 benign lesions in 38 patients with prostate cancer were retrospectively analyzed. Maximum standardized uptake value (SUVmax) for benign and prostate-related malignant lesions were calculated at min 60 and min 120 of PET/CT imaging. In order to calculate SUV ratio, the SUVmax of left gluteus maximus was measured at the same time. The difference of SUVmax metrics and SUV ratio between malignant and benign lesions was statistically analyzed, the cut-off value of ROC curve was calculated, and the diagnostic efficacy of SUVmax index and SUV ratio at two time points was compared.

RESULTS

SUVmax metrics and SUV ratio of early and delayed imaging of PC-related malignant lesions were significantly higher than those of benign lesions (p < 0.05). In terms of individual indicators, the highest accuracy and sensitivity was in the delayed SUV ratio (89.2% and 94.7%), the best specificity was in the early SUVmax (93.0%). When the individual and combined indicators were compared together, the SUV ratio in the delay period still showed the best diagnostic sensitivity and accuracy, and the best specificity were SUVmax early and ▵SUVmax, SUVmax early and RI.

CONCLUSIONS

Uptake of ¹⁸F-DCFPyL increased over time in prostate-associated malignant lesions compared with benign tissue. For single-phase imaging, 2-hour (delayed) imaging has better diagnostic performance. However, the dual-phase imaging (1 and 2 h) are helpful in the differential diagnosis of prostate-associated malignant lesions and benign lesions.

The Value of Multimodality PET/CT Imaging in Detecting Prostate Cancer Biochemical Recurrence

Prostate cancer (PCa) induced death is the predominant cause of cancer-related death among men in 48 countries. After radical treatment, biochemical recurrence has become an important factor for prognosis. The early detection and diagnosis of recurrent lesions are very helpful in guiding treatment and improving the prognosis. PET/CT is a promising method for early detection of lesions in patients with biochemical recurrence of prostate cancer. This article reviews the progress of the research on PET/CT in the PCa biochemical recurrence and aims to introduce new technologies and provide more direction for future research.

False-Positive Uptake in Splenic Hemangioma on 68Ga-PSMA PET/CT Scan for Late Biochemical Recurrence of Prostate Cancer

ABSTRACT

A 71-year-old man underwent 68Ga-PSMA PET/CT for evaluation of a late biochemical recurrence after radical prostatectomy. An intense PSMA uptake was identified in spleen. Additional evaluation with a contrast-enhanced MRI showed a splenic lesion consistent with splenic hemangioma.

PET/CT variants and pitfalls in prostate cancer: What you might see on PET and should never forget

2-deoxy-2-[¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) gained an impressive role in the diagnostic management of many oncological diseases, even though its use in imaging prostate cancer (PC) is limited to selected cases, mostly advanced stage of PC and selection for prostate specific antigen membrane (PSMA) radioligand therapy (RLT). In the past years, several PET tracers have been developed for both staging and restaging PC. The three most employed PET molecules in daily practice are [¹¹C] or [¹⁸F]F-Choline, [¹⁸F]F-Fluciclovine (Anti-1- amino-3-[18F]Fluorocyclobutane-1-Carboxylic Acid, also known as (Anti-[¹⁸F]FACBC), [⁶⁸Ga]Ga-PSMA and recently FDA approved the first Fluorinated PSMA-based named [¹⁸F]F-DCFPyl. Each one has its own physiological and peculiarity which are worth exploring. Moreover, an increasing number of case reports and studies have reported tracers' variants, pitfalls, or even non-prostatic diseases (benign and malignant) incidentally detected. In prostate oncology, PET can be performed with several indications in different stages of disease, as highlighted in the EAU Guidelines on PC. A correct scan interpretation depends on the knowledge of both the physiological distribution of the tracers and the uptake of possible variants and pitfalls. The aim of this critical review is to provide a comprehensive knowledge of physiological distribution of these three tracers, as well as an updated overview of variants and pitfalls.

Hemangioblastoma: An Unsuspected Pitfall in PSMA PET/CT

ABSTRACT

Hemangioblastoma (HB) is the most common primary intra-axial posterior fossa tumor in adults and is a benign vascular neoplasm. We report the case of a 73-year-old man suffering from biochemical recurrence of prostate cancer where intense overexpression of prostate-specific membrane antigen (PSMA) was observed in HB in a PSMA PET/CT. Overexpression of PSMA in tumor-associated vascular structures has been proposed as an explanation of PSMA ligand uptake in several nonprostatic tumors. Given the pathological nature of HB, this mechanism may explain the intense overexpression of PSMA observed in present case.

Does Prostate-Specific Membrane Antigen Avidity of Vertebral Hemangioma Change?

ABSTRACT

Vertebral hemangiomas are the most common benign tumors of the spine and mostly occur in the thoracic spine. Mostly they are detected incidentally during imaging studies for other reasons. We present the case of vertebral hemangioma that showed prostate-specific membrane antigen uptake in the second 68Ga-prostate-specific membrane antigen PET/CT, whereas no uptake was observed in the initial study.

Skull vault hemangioma mimicking neoplastic lesion on [68Ga]Ga-PSMA-11 PET/CT in a patient with glioblastoma: A case report

We present the case of a 47-year-old woman treated by radiochimotherapy for a glioblastoma which underwent a [68Ga]Ga-PSMA-11-PET/CT to distinguish postradiation changes from an evolutionary process. This demonstrated a weak homogeneous uptake surrounding the lesion. There was a focal and moderate uptake of a pseudo lytic skull diploe lesion near to the glioblastoma, finally attributed to a calvaria hemangioma. Calvaria hemangiomas are less frequent than vertebral hemangiomas and may demonstrate a modest PSMA uptake that one should keep in mind so as not to misinterpret the examination in patients followed for glioblastomas.

Solitary rib lesions showing prostate-specific membrane antigen (PSMA) uptake in pre-treatment staging 68 Ga-PSMA-11 positron emission tomography scans for men with prostate cancer: benign or malignant?

OBJECTIVES

To determine the proportion of solitary rib lesions on pre-treatment ⁶⁸ Gallium-labelled prostate-specific membrane antigen (PSMA)/computed tomography (CT) scans in men with prostate cancer that are malignant and examine any predictive factors.

PATIENTS AND METHODS

This retrospective single tertiary referral institution cohort study of men reviewed the results of ⁶⁸ Ga-PSMA-11 positron emission tomography (PET)/CT scans performed for primary staging prior to treatment of prostate cancer from July 2014 to September 2019. Men with PSMA uptake outside the prostate in only the rib lesion were included. A solitary rib lesion was considered to be malignant if it increased in size on follow-up imaging. A lesion was considered benign if the prostate-specific antigen (PSA) level remained <0.1 µg/L following a radical prostatectomy (RP), <2 µg/L above nadir following radiotherapy (RT) as per the Phoenix criteria, histology was benign on rib biopsy, or follow-up imaging showed no growth of the rib lesion. If a lesion did not meet these criteria it was considered indeterminate.

RESULTS

A total of 62 men had PSMA uptake in a solitary rib lesion; 54 went on to have RPs and eight underwent RT. In all, 61 of the men (98.4%) met the criteria for a benign rib lesion. Only one man had a false-negative malignant lesion. This man had a rib lesion with a low maximum standardised uptake value (SUV_max ) of 2.21 reported as benign, but the postoperative PSA level was 0.67 µg/L and the rib lesion progressed on follow-up imaging, with development of widespread metastases. Of the benign rib lesions, there were four false positives reported as possible metastases. Three had percutaneous rib biopsies, two of which came back with benign histology and one was indeterminate. The indeterminate biopsy patient had a RP and his postoperative PSA level was <0.1 µg/L. A total of 43 (69.4%) men with benign rib lesions had a SUV_max greater than the SUV_max of the malignant lesion.

CONCLUSION

To our knowledge, this is the first cohort study of men with PSMA-avid solitary rib lesions on pre-treatment ⁶⁸ Ga-PSMA PET/CT staging scans for prostate cancer. Our results indicate that the vast majority of these lesions have low-intensity uptake and are benign. Intervention to confirm this is not usually required.

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.

Factors Predicting Metastatic Disease in 68Ga-PSMA-11 PET-Positive Osseous Lesions in Prostate Cancer

Bone is the most common site of distant metastatic spread in prostate adenocarcinoma. Prostate-specific membrane antigen (PSMA) uptake has been described in both benign and malignant bone lesions, which can lead to false-positive findings on ⁶⁸Ga-PSMA-11 PET. The purpose of this study was to evaluate the diagnostic accuracy of ⁶⁸Ga-PSMA-11 PET for osseous prostate cancer metastases and improve bone uptake interpretation using semiquantitative metrics. Methods: Fifty-six prostate cancer patients (18 before prostatectomy and 38 with biochemical recurrence) who underwent ⁶⁸Ga-PSMA-11 PET/MRI or PET/CT examinations with osseous PSMA-ligand uptake were included in the study. Medical records were reviewed retrospectively by board-certified nuclear radiologists to determine true or false positivity based on a composite endpoint. For each avid osseous lesion, we measured biologic volume; size; PSMA Reporting and Data System (RADS) rating; SUV_max; and ratio of lesion SUV_max to liver, blood pool, and background bone SUV_max Differences between benign and malignant lesions were evaluated for statistical significance, and cutoffs for these parameters were determined to maximize diagnostic accuracy. Results: Among 56 participants, 13 (22.8%) had false-positive osseous ⁶⁸Ga-PSMA-11 findings and 43 (76.8%) had true-positive osseous ⁶⁸Ga-PSMA-11 findings. Twenty-two patients (39%) had 1 osseous lesion, 18 (32%) had 2-4 lesions, and 16 (29%) had 5 or more lesions. Cutoffs resulting in statistically significant (P < 0.005) differences between benign and malignant lesions were a PSMA RADS rating of at least 4, an SUV_max of at least 4.1, and SUV_max ratios of at least 2.11 for lesion to blood pool, at least 0.55 for lesion to liver, and at least 4.4 for lesion to bone. These measurements corresponded to a lesion-based ⁶⁸Ga-PSMA-11 PET lesion detection rate of 80%, 93%, 89%, 21%, and 89%, respectively, for malignancy, and a specificity of 73%, 73%, 73%, 93%, and 60%, respectively. Conclusion: PSMA RADS rating, SUV_max, and SUV_max ratio for lesion to blood pool can help differentiate benign from malignant lesions on ⁶⁸Ga-PSMA-11 PET. An SUV_max ratio of more than 2.2 for lesion to blood pool is a reasonable parameter to support image interpretation and presented a superior lesion detection rate and specificity when compared with visual interpretation by PSMA RADS. These parameters hold clinical value by improving diagnostic accuracy for metastatic prostate cancer on ⁶⁸Ga-PSMA-11 PET/MRI and PET/CT.

Nonprostatic diseases on PSMA PET imaging: a spectrum of benign and malignant findings

PSMA PET imaging was originally used to assess biochemical recurrence of prostate cancer (PCa), but its clinical use was promptly extended to detection, staging and therapy response assessment. The expanding use of PSMA PET worldwide has also revealed PSMA ligand uptake in diverse nonprostatic diseases, which raised questions about the specificity of this imaging modality. Although not very common initially, a growing number of pathologies presenting PSMA uptake on PET have been reported in the last few years, and a proper interpretation of PSMA PET imaging findings suddenly became challenging and, to some extent, confusing. Compared to cytoplasmic PSMA expression in nonprostatic cells, the molecular features of apical PSMA expression in PCa cells can help to distinguish these various conditions. Correlations of imaging findings to patient history, to the expected pattern of disease spread and mainly to computed tomography (CT) and/or magnetic resonance imaging (MRI) characteristics will reinforce the distinction of lesions that are more likely related to PCa from those that could lead to an incorrect diagnosis. The overall benefits of endothelial PSMA expression, which is associated with the neovasculature of malignant neoplasms, will be highlighted, stating the potential use of PSMA ligand uptake as a theranostic tool. This review aims to cover the collection of nonprostatic diseases, including benign and malignant tumors, in a didactic approach according to disease etiology, with discussion of bone-related conditions and inflammatory and infectious processes.

Heterogeneity of 68Ga-PSMA PET/CT Uptake in Fibrous Dysplasia

Fibrous dysplasia is an uncommon benign bone pathology with only rare potential for malignant transformation. We describe the heterogeneous uptake of fibrous dysplasia of a whole rib on Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT. Ga-PSMA binds to PSMA-expressing prostate cancer cells, but it can also bind to the neovasculature of various solid tumors, as well as to some benign lesions. Ga-PSMA expression in fibrous dysplasia should not automatically be equated with malignant transformation or confused with prostate cancer metastases.

68Ga-PSMA Uptake in Escherichia coli Spondylodiscitis

In a patient with recently diagnosed intermediate-risk prostate cancer, Ga-prostate-specific-membrane-antigen (PSMA) PET/CT for primary staging discovered increased Ga-PSMA uptake in spondylodiscitis in the thoracic spine. The bacteria Escherichia coli was found both in blood cultures and bone biopsies from the thoracic lesion. This case presents spondylodiscitis as a potential benign pitfall to be aware of when interpreting PSMA PET/CT in prostate cancer patients.

Incidental Detection of a Radiation-Induced Soft-Tissue Sarcoma on 68Ga-PSMA PET/CT in a Patient Previously Treated for Prostate Cancer

Radiation-induced sarcoma is a rare complication of radiation therapy. We describe the incidental detection of a radiation-induced undifferentiated soft-tissue sarcoma with increased uptake on Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT in a prostate cancer patient previously treated with surgery and external-beam radiotherapy. Results were confirmed by histological analysis. Ga-PSMA is known to bind not only to PSMA-expressing prostate cancer cells but also to the neovasculature of various other solid tumors. A careful Ga-PSMA PET/CT review of previously irradiated areas is warranted so as not to miss radiation-induced sarcoma in prostate cancer patients.

Avid 68Ga-PSMA Uptake in Accessory Submandibular Salivary Gland

Accessory submandibular salivary gland (ASSG) is an extremely rare variation of the submandibular salivary gland. We reported a 65-year-old man with prostate cancer underwent Ga-PSMA PET/CT for active surveillance. The images showed abnormal PSMA uptake adjacent to the submandibular salivary gland without abnormal activity distribution in the rest regions of the body. The lesion density was similar to that of the submandibular salivary gland. Pathological biopsy confirmed that it was an ASSG. Our case illustrates that ASSG is an addition benign cause of extraprostatic uptake of PSMA.

68Ga-PSMA PET/CT-based metastasis-directed radiotherapy for oligometastatic prostate cancer recurrence after radical prostatectomy

PURPOSE

The aim of this communication was to assess the efficacy of directed oligometastatic radiotherapy (RT) based on ⁶⁸Ga-PSMA PET/CT in patients with prostate cancer (PCa) biochemical relapse (BCR) after primary treatment with curative intent.

METHODS

This is a retrospective analysis of a monocentric cohort of PCa patients diagnosed with oligometastatic disease on ⁶⁸Ga-PSMA PET/CT and treated with metastasis-directed RT. Inclusion criteria were: histologically proven PCa, BCR after primary treatment with curative intent, oligometastatic disease defined as ≤ 3 metastatic lesions. To evaluate the efficacy of the therapy, biochemical response defined as a decrease of > 50% of PSA (PSA₅₀) was measured at 1 and 4 months. Patients were followed up until progression and start of androgen deprivation therapy (ADT). BCR-free survival and ADT-free survival were calculated.

RESULTS

20 patients met the inclusion criteria. Median PSA value: 1.4 ng/ml (IQR, 0.3-2.3 ng/ml). A total of 30 PSMA-positive lesions were treated: 18 lymph nodes (60%), nine bone (30%) and three visceral lesions (10%). Median follow-up was 15 months (range 4-33 months). Biochemical response at 1 and 4 months was found in 3/20 patients (15%) and 14/20 (70%), respectively. BCR-free survival rate at 1 year was 79% and 53% at 2 years. ADT-free survival at 2 years was 74%.

CONCLUSION

This retrospective study suggests that metastasis-directed RT based on ⁶⁸Ga-PSMA PET/CT may be a valuable treatment in patients with PCa oligometastatic disease, providing promising BCR-free survival rates and potentially postponing ADT for at least 2 years in 74% of the patients. Response assessment should not be measured before 4 months after treatment.

Rib Fractures Mimicking Bone Metastases in 18F-PSMA-1007 PET/CT for Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a membrane glycoprotein that is overexpressed in prostate cancer cells. It is also expressed in other normal tissues and several other malignant and benign diseases. We present a case of a 69-year-old man with history of prostate adenocarcinoma who underwent F-PSMA-1007 PET/CT due to suspected biochemical recurrence. PET/CT showed F-PSMA-1007 uptake in healing rib fractures with no other pathologic findings. Clinicians reporting F-PSMA-1007 PET/CT should be aware of this potential pitfall, especially in nontypical trauma pattern (eg, solitary osseous lesion) mimicking bone metastases.

Importance of 68Ga-PSMA PET/CT in hospital practice. View of the radiation oncologist

Radiotherapy is a treatment with curative intent, both in patients with primary diagnosis of prostate cancer (PCa) and in patients presenting with biochemical recurrence after radical prostatectomy (RP). Moreover, the use of stereotactic body radiotherapy as a metastasis directed therapy in patients with oligometastatic PCa has significantly increased in the recent years. Conventional imaging techniques, including transrectal ultrasound, computed tomography (CT), morphologic magnetic resonance and bone scintigraphy have traditionally played a minor role in all those clinical scenarios due to its low diagnostic accuracy. The recent development of the positron emission tomography (PET) radiotracer ⁶⁸Ga-PSMA binding to the prostate specific membrane antigen (PSMA), a transmembrane glycoprotein overexpressed in PCa cells, has shown promising results. Detection rates for PCa lesions are higher than CT and higher than the best technique available, the PET/CT with choline. Its superiority has been demonstrated even at very low PSA levels (<1 ng/ml). This increase in diagnostic accuracy represents a potential impact on patient management, especially in radiotherapy. Even if this imaging technique is already available for routine clinical practice in some European countries, in Spain, unfortunately, there is very limited access. In this review, we analyze the main studies that investigate the usefulness of ⁶⁸Ga-PSMA PET/CT in patients with PCa and its potential impact on radiotherapy treatments. In addition, we compared the ⁶⁸Ga-PSMA PET/CT, with the multiparametric magnetic resonance imaging and the PET/CT with choline, in the different clinical scenarios.

An Incidental Finding of Subcutaneous Hemangioma During 99mTcO4 Salivary Gland Scintigraphy

A 43-year-old woman with papillary thyroid cancer prepared for I ablation after total thyroidectomy. With a history of type 2 diabetes for 10 years, she recently presented with periodontitis, candidiasis, and mouth dryness. TcO4 scintigraphy was ordered to evaluate function of the salivary glands. The scintigraphy incidentally found a focal TcO4 uptake in the left supraclavicular region. The subsequent neck ultrasonography showed a hypoechoic soft tissue mass with heterogeneous hypervascularity, suggestive of hemangioma.

[68Ga]PSMA-HBED-CC Uptake in Osteolytic, Osteoblastic, and Bone Marrow Metastases of Prostate Cancer Patients

PURPOSE

The aim of this study was to evaluate potential differences in "Glu-NH-CO-NH-Lys" radio-labeled with [⁶⁸Ga]gallium N,N-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N-diacetic acid ([⁶⁸Ga]PSMA-HBED-CC) uptake in osteolytic, osteoblastic, mixed, and bone marrow metastases in prostate cancer (PC) patients.

PROCEDURES

This retrospective study was approved by the local ethics committee. Patients who received [⁶⁸Ga]PSMA-HBED-CC positron emission tomography/computed tomography ([⁶⁸Ga]PSMA-PET/CT) with at least one positive bone metastasis were included in this study. Only patients who have not received systemic therapy for their PC were included. Bone metastases had to be confirmed by at least one other imaging modality or follow-up investigation. The maximum standardized uptake value (SUV_max) and mean Hounsfield units (HU_mean) of each metastasis were measured. Based on CT, each metastasis was classified as osteolytic (OL), osteoblastic (OB), bone marrow (BM), or mixed (M).

RESULTS

One hundred fifty-four bone metastases in 30 patients were evaluated. Eighty out of 154 (51.9%) metastases were classified as OB, 21/154 (13.6%) as OL, 23/154 (14.9%) as M, and 30/154 (19.5%) as BM. The SUV_max for the different types of metastases were 10.6 ± 7.07 (OB), 24.0 ± 19.3 (OL), 16.0 ± 21.0 (M), and 14.7 ± 9.9 (BM). The SUV_max of OB vs. OL and OB vs. BM metastases differed significantly (p ≤ 0.025). A significant negative correlation between HU_mean and SUV_max (r = -0.23, p < 0.05) was measured.

CONCLUSIONS

[⁶⁸Ga]PSMA-HBED-CC uptake is higher in osteolytic and bone marrow metastases compared to osteoblastic metastases. Information derived from [⁶⁸Ga]PSMA-PET and CT complement each other for the reliable diagnosis of the different types of bone metastases in PC patients.

Benign Traumatic Rib Fracture: A Potential Pitfall on 68Ga-Prostate-Specific Membrane Antigen PET/CT for Prostate Cancer

Two, respectively, 72- and 76-year-old men with recently diagnosed high-risk prostate cancer were referred for primary staging with Ga-prostate-specific membrane antigen (PSMA) PET/CT. In both patients, the PET scans revealed increased Ga-PSMA uptake in, respectively, 3 and 4 rib fractures, characteristically placed as "pearls on a string." These cases illustrate important pitfalls when reporting PSMA PET.

68Ga-PSMA-HBED-CC Uptake in Cervical, Celiac, and Sacral Ganglia as an Important Pitfall in Prostate Cancer PET Imaging

The study aims to investigate the presence of physiologic prostate-specific membrane antigen (⁶⁸Ga-PSMA)-ligand uptake on PET in cervical, celiac, and sacral ganglia of the sympathetic trunk as a pitfall for lymph node metastases in prostate cancer imaging. Methods: Four hundred seven patients who underwent Glu-NH-CO-NH-Lys radiolabeled with ⁶⁸Ga-gallium N,N-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N-diacetic acid (⁶⁸Ga-PSMA-HBED-CC) PET (combined with a diagnostic CT) were retrospectively analyzed. The number of ⁶⁸Ga-PSMA PET-positive cervical, celiac, and sacral ganglia was determined, and the configuration and SUV_max of each ganglion were measured. In addition, the configuration and SUV_max of adjacent lymph node metastases in the respective region (cervical, celiac, or sacral) were determined. Results:⁶⁸Ga-PSMA-ligand uptake above background was detected in 401 (98.5%) patients in any peripheral ganglia, in 369 (92%) patients in cervical ganglia, in 363 (89%) patients in celiac ganglia, and in 183 (46%) patients in sacral ganglia. The ⁶⁸Ga-PSMA-ligand uptake was highest in celiac (mean SUV_max, 2.9 ± 0.8 vs. cervical mean SUV_max, 2.4 ± 0.6) and sacral (mean SUV_max 1.7 ± 0.5; both P < 0.0001) ganglia. Intraindividually there was a statistically significant but weak to moderate correlation between the ⁶⁸Ga-PSMA-ligand uptake in cervical versus celiac ganglia (R = 0.34, P < 0.0001), cervical versus sacral (R = 0.52, P < 0.0001), and celiac versus sacral (R = 0.16, P < 0.05). The ⁶⁸Ga-PSMA-ligand uptake was significantly more intense in adjacent lymph node metastases than the respective ganglia (cervical: 18.0 ± 16.2 vs. 2.4 ± 0.6, P < 0.0001; celiac: 13.5 ± 12.3 vs. 2.9 ± 0.8, P < 0.0001; sacral: 13.4 ± 11.6 vs. 1.7 ± 0.5, P < 0.0001). Furthermore, ganglia predominantly exhibit a band-shaped configuration (71.2%), followed by a teardrop (26.8%) and only rarely a nodular configuration (2.0%). Conversely, lymph node metastases are only rarely band-shaped (1.1%), but more often show teardrop (40.3%) or nodular appearance (58.6%) (P < 0.00001). Conclusion:⁶⁸Ga-PSMA-ligand uptake in ganglia along the sympathetic trunk as assessed by ⁶⁸Ga-PSMA-HBED-CC PET represents an important pitfall in prostate cancer PET imaging. The ⁶⁸Ga-PSMA-ligand uptake is higher in celiac ganglia than cervical or sacral ganglia, and the level of ⁶⁸Ga-PSMA-ligand uptake seems to be patient-related. For the differentiation between lymph node metastases and sympathetic ganglia, both intensity of ⁶⁸Ga-PSMA-ligand uptake and exact localization and configuration of the respective lesion should be examined carefully.

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.