Is 68Ga-Prostate-Specific Membrane Antigen PET/CT Superior than 18F-FDG PET/CT for Evaluation of Metastatic Osteosarcoma?

Primary Prostatic Stromal Sarcoma on 18 F-PSMA PET/CT

ABSTRACT

Primary prostatic stromal sarcoma is extremely rare. Serum PSA is usually normal. Here, we report a case of primary prostatic stromal sarcoma in a 23-year-old man. 18 F-prostate-specific membrane antigen (PSMA) PET/CT showed prostate mass and multiple low-density lesions in the liver with high PSMA expression. However, after chemotherapy, the level of PSMA expression in the prostate mass decreased, and PSMA expression lesions in the liver disappeared.

Sternum Metastases: From Case-Identifying Strategy to Multidisciplinary Management

We aimed to overview the most recent data on sternal metastases from a multidisciplinary approach (diagnosis strategies, outcome, and histological reports). This narrative review based on a PubMed search (between January 2020 and 22 July 2023) using key words such as "sternal", "manubrium", and "metastasis" within the title and/or abstract only included original papers that specifically addressed secondary sternal spreading of cancer in adults, for a total of 48 original articles (14 studies and 34 single case reports). A prior unpublished case in point is also introduced (percutaneous incisional biopsy was used to address a 10 cm sternal tumour upon first admission on an apparently healthy male). The studies (n = 14) may be classified into one of three groups: studies addressing the incidence of bone metastases (including sternum) amid different primary cancers, such as prostate cancer (N = 122 with bone metastases, 83% of them with chest wall metastases), head and neck cancers (N = 3620, 0.8% with bone metastases, and 10.34% of this subgroup with sternum involvement); and glioblastoma (N = 92 with bone metastases, 37% of them with non-vertebral metastases, including the sternum); assessment cohorts, including breast cancer (N = 410; accuracy and sensitivity of PET/CT vs. bone scintigraphy is superior with concern to sternum spreading) and bone metastases of unknown origin (N = 83, including a subgroup with sternum metastases; some features of PET/CT help the differentiation with multiple myeloma); and cohorts with various therapeutic approaches, such as palliative arterial embolization (N = 10), thymic neuroendocrine neoplasia (1/5 detected with sternum metastases), survival rates for sternum metastases vs. non-sternum chest wall involvement (N = 87), oligo-metastatic (sternal) breast cancer (3 studies, N = 16 for all of them), oligo-metastatic head and neck cancer (N = 81), conformal radiotherapy (N = 24,215, including an analysis on sternum spreading), and EBRT followed by MR-HIFU (N = 6). Core data coming from the isolated case reports (N = 34) showed a female to male ratio of 1.6; the females' ages were between 34 and 80 (mean of 57.28) and the males' ages varied between 33 and 79 (average of 58.78) years. The originating tumour profile revealed that the most frequent types were mammary (N = 8, all females) and thyroid (N = 9, both women and men), followed by bladder (N = 3), lung (N = 2), and kidney (N = 2). There was also one case for each of the following: adenoid cystic carcinoma of the jaw, malignant melanoma, caecum MiNEN, a brain and an extracranial meningioma, tongue carcinoma, cholangiocarcinoma, osteosarcoma, and hepatocellular carcinoma. To our knowledge, this is the most complex and the largest analysis of prior published data within the time frame of our methods. These data open up new perspectives of this intricate, dynamic, and challenging domain of sternum metastases. Awareness is a mandatory factor since the patients may have a complex multidisciplinary medical and/or surgical background or they are admitted for the first time with this condition; thus, the convolute puzzle will start from this newly detected sternal lump. Abbreviations: N = number of patients; n = number of studies; PET/CT = positron emission tomography/computed tomography; EVRT = external beam radiotherapy; MR-HIFU = magnetic resonance-guided high-intensity focused ultrasound; MiNEN = mixed neuroendocrine-non-neuroendocrine tumour.

Prostate-specific membrane antigen (PSMA) as a potential target for molecular imaging and treatment in bone and soft tissue sarcomas

Bone and soft tissue sarcomas are a group of rare malignant tumours with major histological and anatomical varieties. In a metastatic setting, sarcomas have a poor prognosis due to limited response rates to chemotherapy. Radioligand therapy targeting prostate-specific membrane antigen (PSMA) may offer a new perspective. PSMA is a type II transmembrane glycoprotein which is present in all prostatic tissue and overexpressed in prostate cancer. Despite the name, PSMA is not prostate-specific. PSMA expression is also found in a multitude of non-prostatic diseases including a subgroup of sarcomas, mostly in its neovascular endothelial cells. On PET/CT imaging, multiple sarcomas have also shown intense PSMA-tracer accumulation. PSMA expression and PSMA-tracer uptake seem to be highest in patients with aggressive and advanced sarcomas, who are also in highest need of new therapeutic options. Although these results provide a good rationale for the future use of PSMA-targeted radioligand therapy in a selection of sarcoma patients, more research is needed to gain insight into optimal patient selection methods, PSMA-targeting antibodies and tracers, administered doses of radioligand therapy, and their efficacy and tolerability. In this review, mRNA expression of the FOLH1 gene which encodes PSMA, PSMA immunohistochemistry, PSMA-targeted imaging and PSMA-targeted therapy in sarcomas will be discussed.

PSMA Expression in Solid Tumors beyond the Prostate Gland: Ready for Theranostic Applications?

In the past decades, the expanding use of prostate-specific membrane antigen (PSMA) imaging for prostate cancer has led to the incidental detection of a lot of extra-prostatic malignancies showing an increased uptake of PSMA. Due to these incidental findings, the increasing amount of immunohistochemistry studies and the deeper knowledge of the mechanisms of expression of this antigen, it is now clear that “PSMA” is a misnomer, since it is not specific to the prostate gland. Nevertheless, this lack of specificity could represent an interesting opportunity to bring new insights on the biology of PSMA and its sites of expression to image and treat new conditions, particularly several cancers. In this review, we will describe the main extra-prostatic cancers that exhibit PSMA expression and that can be studied with PSMA-based positron emission tomography–computed tomography (PET/CT) as an additional or alternative tool to conventional imaging. In particular, we will focus on cancers in which a radioligand therapy with ¹⁷⁷lutetium has been attempted, aiming to provide an overview of the possible future theragnostic applications of PSMA.

Bone Uptake in Prostate Cancer Patients: Diagnostic Performances of PSMA-RADS v1.0, Clinical, Biological, and 68 Ga-PSMA-11 PET Features to Predict Metastasis After Biochemical Recurrence

PURPOSE

68 Gallium-labeled prostate-specific membrane antigen-11 (PSMA) PET/CT is the new reference to identify relapse during biochemical recurrence of prostate cancer (PCa). However, this method lacks specificity for bone foci. This study aimed to report the prevalence of PCa bone metastases and to assess the diagnostic performances of PSMA reporting and data systems (RADS), clinical, biological, and imaging features for identification.

PATIENTS AND METHODS

A multicentric retrospective cohort of consecutive patients with biochemical recurrence after local treatment was analyzed. Clinical and biological features at initial staging and during recurrence were retrieved from medical reports. The metastatic status of each bone uptake on PSMA PET/CT was determined according to histopathology, comparisons with concomitant and previous conventional imaging, prostate-specific antigen kinetic, and follow-up. Two nuclear medicine physicians assessed PSMA-RADS, anatomic location, radiological patterns, SUV max , and the presence of other molecular lesions. Univariate and multivariate analyses were conducted to identify independent predictors of PCa metastases.

RESULTS

In the eligible population, 98/298 patients (32.9%) showed bone uptake on PSMA PET/CT. In patients with a final diagnosis, 28/81 lesions (34.6%) were metastases. PSMA-RADS-4 or 5 showed sensitivity of 79%, specificity of 94%, and accuracy of 89%. PSMA-RADS had a significantly higher area under the receiver operating characteristic curve than the initial reading in clinical practice (0.91 vs 0.83, P = 0.0074). Initial Gleason score ≥8, age ≤71 years at recurrence, and SUV max >6.21 were independent predictors of PCa metastases in multivariate logistic regression ( P = 0.0314, 0.0179, and 0.0003, respectively).

CONCLUSIONS

Most bone uptakes at PSMA PET/CT were benign lesions. PSMA-RADS, patients and tumor characteristics, and SUV max could help identify PCa bone metastases.