Spinal Tuberculosis Mimicking as Prostate Cancer Metastases in Ga-68 Prostate-specific Membrane Antigen Positron-emission Tomography/Computed Tomography

Case report: Systemic tuberculosis with prostate involvement mimicking prostate cancer with multiple metastases on 18F-FDG and 18F-PSMA PET/CT

Background

Prostate tuberculosis is a common form of urogenital tuberculosis that occurs in men. Clinical and imaging manifestations of prostate tuberculosis are atypical, which often need to be differentiated from benign prostatic hyperplasia, a prostate malignant tumor, and a urinary tract infection. Although prostate-specific membrane antigen (PSMA) is considered a specific biomarker for prostate cancer, it is also found within tuberculosis tissues that may be stimulated by angiogenic factors. An abnormal PSMA uptake on positron emission tomography combined with computed tomography (PET/CT) should eliminate the possibility of tuberculosis.

Case report

In this study, we reported a case of a 51-year-old man with an elevated erythrocyte sedimentation rate (ESR) but a normal prostate-specific antigen (PSA) value. 2-Deoxy-2-[fluorine-18]-fluoro-D-glucose (18F-FDG) and [fluorine-18]-prostate-specific membrane antigen (18F-PSMA) PET/CT scans were performed for further evaluation. The prostate showed a high fluoro-D-glucose (FDG) uptake but a slight PSMA uptake. Multiple osteolytic bone destruction and lymph nodes with an increased FDG uptake but a mild PSMA uptake were observed throughout the body. Systemic tuberculosis was diagnosed based on the prostate biopsy and the positive result of the T-cell spot test regarding tuberculosis infection. After 6 months of standard anti-tuberculosis treatment, the patient experienced symptom relief.

Conclusion

In the case of a urinary tract infection, where the prostate shows high FDG uptake lesions with perilesional abscess, a mildly increased PSMA uptake, a low PSA value, a high ESR, and relevant clinical symptoms, tuberculosis should be considered and laboratory tests are required, especially when symptoms are relieved after successful anti-tuberculosis therapy. The final confirmation of the diagnosis still relies on pathological examination.

Incidental Identification of Osteoid Osteoma of Skull Bone on 68 Ga-PSMA PET/CT

ABSTRACT

An osteoid osteoma (OO) is a benign bone neoplasm, characterized by significant nocturnal pain that usually responds to nonsteroidal anti-inflammatory drugs. It occurs most commonly in the lower extremities and vertebrae. Here, we present a case of carcinoma prostate, who was referred to our department for 68 Ga-PSMA PET/CT scan, and we incidentally found out PSMA-avid OO involving frontal bone of skull, which is a rare finding. To the best of our knowledge, this is the second case in which high PSMA uptake is found in the OO, suggesting a possible PSMA expression related to osteoblastic activity.

Active Lumbar Spondylodiscitis on [68Ga]Ga-PSMA-11 PET/CT Mimicking Bone Metastasis

We report a [68Ga]Ga-PSMA-11 positron emission tomography/computed tomography (PET/CT) scan of a 71-year-old man with metastatic castration-resistant prostate cancer (mCRPC) and concomitant active lumbar spondylodiscitis, both PSMA-positive on a PET/CT scan. This interesting image should advise colleagues to consider spondylodiscitis as a differential diagnosis of PSMA-positive findings in the spine, particularly if intervertebral space and soft tissue are involved.

Molecular Imaging of Tuberculosis

Despite the introduction of many novel diagnostic techniques and newer treatment agents, tuberculosis (TB) remains a major cause of death from an infectious disease worldwide. With about a quarter of humanity harboring Mycobacterium tuberculosis, the causative agent of TB, the current efforts geared towards reducing the scourge due to TB must be sustained. At the same time, newer alternative modalities for diagnosis and treatment response assessment are considered. Molecular imaging entails the use of radioactive probes that exploit molecular targets expressed by microbes or human cells for imaging using hybrid scanners that provide both anatomic and functional features of the disease being imaged. Fluorine-18 fluorodeoxyglucose (FDG) is the most investigated radioactive probe for TB imaging in research and clinical practice. When imaged with positron emission tomography interphase with computed tomography (PET/CT), FDG PET/CT performs better than sputum conversion for predicting treatment outcome. At the end of treatment, FDG PET/CT has demonstrated the unique ability to identify a subset of patients declared cured based on the current standard of care but who still harbor live bacilli capable of causing disease relapse after therapy discontinuation. Our understanding of the pathogenesis and evolution of TB has improved significantly in the last decade, owing to the introduction of FDG PET/CT in TB research. FDG is a non-specific probe as it targets the host inflammatory response to Mycobacterium tuberculosis, which is not specifically different in TB compared with other infectious conditions. Ongoing efforts are geared towards evaluating the utility of newer probes targeting different components of the TB granuloma, the hallmark of TB lesions, including hypoxia, neovascularization, and fibrosis, in TB management. The most exciting category of non-FDG PET probes developed for molecular imaging of TB appears to be radiolabeled anti-tuberculous drugs for use in studying the pharmacokinetic characteristics of the drugs. This allows for the non-invasive study of drug kinetics in different body compartments concurrently, providing an insight into the spatial heterogeneity of drug exposure in different TB lesions. The ability to repeat molecular imaging using radiolabeled anti-tuberculous agents also offers an opportunity to study the temporal changes in drug kinetics within the different lesions during treatment.

Tuberculosis: Role of Nuclear Medicine and Molecular Imaging With Potential Impact of Neutrophil-Specific Tracers

With Tuberculosis (TB) affecting millions of people worldwide, novel imaging modalities and tools, particularly nuclear medicine and molecular imaging, have grown with greater interest to assess the biology of the tuberculous granuloma and evolution thereof. Much early work has been performed at the pre-clinical level using gamma single photon emission computed tomography (SPECT) agents exploiting certain characteristics of Mycobacterium tuberculosis (MTb). Both antituberculous SPECT and positron emission tomography (PET) agents have been utilised to characterise MTb. Other PET tracers have been utilised to help to characterise the biology of MTb (including Gallium-68-labelled radiopharmaceuticals). Of all the tracers, 2-[¹⁸F]FDG has been studied extensively over the last two decades in many aspects of the treatment paradigm of TB: at diagnosis, staging, response assessment, restaging, and in potentially predicting the outcome of patients with latent TB infection. Its lower specificity in being able to distinguish different inflammatory cell types in the granuloma has garnered interest in reviewing more specific agents that can portend prognostic implications in the management of MTb. With the neutrophil being a cell type that portends this poorer prognosis, imaging this cell type may be able to answer more accurately questions relating to the tuberculous granuloma transmissivity and may help in characterising patients who may be at risk of developing active TB. The formyl peptide receptor 1(FPR1) expressed by neutrophils is a key marker in this process and is a potential target to characterise these areas. The pre-clinical work regarding the role of radiolabelled N-cinnamoyl –F-(D) L – F – (D) –L F (cFLFLF) (which is an antagonist for FPR1) using Technetium 99m-labelled conjugates and more recently radiolabelled with Gallium-68 and Copper 64 is discussed. It is the hope that further work with this tracer may accelerate its potential to be utilised in responding to many of the current diagnostic dilemmas and challenges in TB management, thereby making the tracer a translatable option in routine clinical care.

Isolated Testicular Metastasis from Prostate Cancer Detected on Ga-68 PSMA PET/CT Scan

Although prostate cancer can metastasize to any part of the body, isolated testicular metastasis is very rare and only few cases have been reported so far. Here we present a case of 65-year-old male patient, known case of prostate adenocarcinoma, referred for ⁶⁸Ga-PSMA PET/CT scan, post radiotherapy, and androgen deprivation therapy, for rising serum PSA levels. He was found to have an isolated testicular metastasis on the scan. This report highlights the importance of ⁶⁸Ga-PSMA PET-CT scan in detecting these unusual and rare sites of metastasis from prostate cancer.