Prostate-specific Membrane Antigen Reporting and Data System Version 2.0

Abstract

Prostate-specific Membrane Antigen Reporting and Data System (PSMA-RADS) was introduced for standardized reporting, and PSMA-RADS version 1.0 allows classification of lesions based on their likelihood of representing a site of prostate cancer on PSMA-targeted positron emission tomography (PET). In recent years, this system has extensively been investigated. Increasing evidence has accumulated that the different categories reflect their actual meanings, such as true positivity in PSMA-RADS 4 and 5 lesions. Interobserver agreement studies demonstrated high concordance among a broad spectrum of ⁶⁸Ga- or ¹⁸F-labeled, PSMA-directed radiotracers, even for less experienced readers. Moreover, this system has also been applied to challenging clinical scenarios and to assist in clinical decision-making, for example, to avoid overtreatment in oligometastatic disease. Nonetheless, with an increasing use of PSMA-RADS 1.0, this framework has shown not only benefits, but also limitations, for example, for follow-up assessment of locally treated lesions. Thus, we aimed to update the PSMA-RADS framework to include a refined set of categories in order to optimize lesion-level characterization and best assist in clinical decision-making (PSMA-RADS version 2.0).

Keywords: Prostate carcinoma; Prostate-specific membrane antigen; Reporting and data system; Structured reporting.

Fig. 1 –

PSMA-RADS 1: whole-body maximum-intensity-projection image of a patient with biochemically recurrent PC imaged with ¹⁸F-PSMA-1007. No sites of abnormal uptake can be appreciated. Normal biodistribution of this agent is displayed, including intensive uptake in lacrimal glands, liver, spleen, and kidneys, and low uptake in the small bowel, along with almost no urinary tract excretion of the radiotracer. PC = prostate cancer; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 2 –

PSMA-RADS 1: two patients with biochemically recurrent PC. (A-C) Intense uptake on transaxial ¹⁸F-PSMA-1007 PSMA-PET/CT in a paravertebral structure (arrows), which might be misinterpreted as a lymph node. Instead, this is a typical finding of a cervicothoracic, PSMA-avid ganglion. (D–F) Diffuse uptake pattern in peripheral fibrous changes and ground glass opacities in both lungs (arrows). This patient has shortly recovered from a COVID-19 infection and demonstrated unspecific ¹⁸F-PSmA-1007 uptake in the lower lung. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 3 –

PSMA-RADS 2: two patients with biochemically recurrent PC and likely benign findings. The first patient had pronounced degenerative changes in the thoracic spine with spondylophyte formation. (A) Sagittal CT, (B) sagittal ¹⁸F-PSMA-1007 PET, and (C) fused images revealed intense uptake in a ventral spondylophyte (arrows), most likely caused by degenerative changes. (E) Axial ¹⁸F-PSMA-1007 PET (and (F) axial fused images show mild uptake in a nonenlarged axillary lymph node on (D) axial CT (arrows). Such findings in the axilla (or in hilar or mediastinal lymph nodes) are often unspecific or indicate chronic inflammatory process. Especially if distributed symmetrically, these are not suggestive of PC in the context of biochemical recurrence. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 4 –

PSMA-RADS 3A: two patients with rising PSA levels and equivocal uptake in parailiacal lymph nodes. (A and D) Axial CT, (B and E) axial ¹⁸F-PSMA-1007 PET, and (C and F) axial fused images revealed small (short-axis diameter, <0.8 cm) left parailiacal lymph nodes (arrows). The degree of uptake is only slightly above the background, leaving this finding indeterminate. In general, biopsy of these lymph nodes may be considered. Otherwise, follow-up imaging in 3–6 mo may be recommended. PET = positron emission tomography; PSA = prostate-specific antigen; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 5 –

PSMA-RADS 3B: two patients with recurrent PC and equivocal uptake in bone lesions. (B) Axial ¹⁸F-PSMA-1007 PET and (C) axial fused images showed low focal uptake in a rib without a corresponding lesion in the (A) axial bone window on cT (arrows). (E) Axial ¹⁸F-PSMA-1007 PET and (F) axial fused images with low focal uptake in the left iliac bone without an anatomical correlate in the (D) axial bone window on CT (arrows). Given the high frequency of nonspecific bone uptake with ¹⁸F-PSMA-1007 [38] such lesions can be difficult to categorize and, depending on the clinical context, a score of PSMA-RADS 2 may be appropriate, at times. These focal low-level uptake sites lacking anatomic correlates render these findings indeterminate for early metastatic disease versus benign processes such as traumatic changes or small sites of fibrous dysplasia. Biopsy is often difficult; follow-up imaging may be considered. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 6 –

PSMA-RADS 3C: intense focal uptake in a soft tissue lesion of a patient with biochemically recurrent PC. (A) Axial CT, (B) axial ¹⁸F-PSMA-1007 PET, and (C) axial fused images show exceptionally high uptake in a soft tissue lesion with decent enrichment of contrast agent in the lower spine muscles on the right. Patient’s low PSA level was discordant with this finding. Biopsy of lesion revealed a metastasis of clear cell renal carcinoma that had surgically been removed 13 yr earlier. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSA = prostate-specific antigen; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 7 –

PSMA-RADS 3D: two patients with biochemically recurrent PC and non–radiotracer-avid abnormalities in CT. (A) Axial lung window CT, (B) axial ¹⁸F-PSMA-1007 PET, and (C) axial fused images showed a 1 cm right upper lobe nodule without significant uptake (arrows). Despite equivocal findings on additional ¹⁸F-FDG PET/CT (not shown), the nodule was surgically removed. Histology revealed an atypical carcinoid of the lung. (D) Axial CT, (E) axial ¹⁸F-PSMA-1007 PET, and (F) axial fused images show a 2 cm lymph node adjacent to the left thyroid and the blood vessels (Virchow’s lymph node) and without significant uptake (arrows). The lymph node was surgically removed and histology revealed an infection with mycobacteria other than tuberculosis. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 8 –

PSMA-RADS 4: two patients with biochemically recurrent PC and focal intense uptake without definitive findings on conventional imaging. (A) Axial CT, (B) axial ¹⁸F-PSMA-1007 PET, and (C) axial fused images showed high focal uptake consistent with metastatic PC (arrows). However, because the short-axis diameter of lymph node was 0.3 cm (ie, <1.0 cm), this findings would have been considered benign on CT alone. (E) Axial ¹⁸F-PSMA-1007 PET (F) and axial fused images showed an intensive focal uptake consistent with metastatic PC (arrows), but no anatomic correlates in corresponding (D) axial bone window CT. Considering the typical location of osseous lesion in the spine, this finding is most likely attributable to PC. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data Sytem.

Fig. 9 –

PSMA-RADS 5: two patients with biochemically recurrent PC and focal intensive uptake with corresponding findings on conventional imaging. (A) Axial CT, (B) axial ¹⁸F-PSMA-1007 PET, and (C) axial fused images showed intensive focal uptake in an enlarged right iliac lymph node consistent with metastatic PC (arrows). (E) Axial ¹⁸F-PSMA-1007 PET and (F) axial fused images showed an intensive focal uptake in two ribs and sclerotic changes in corresponding (D) axial bone window CT (arrows). These findings are consistent with metastatic PC. CT = computed tomography; PC = prostate cancer; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.

Fig. 10 –

PSMA-RADS 5T: (A) sagittal bone window CT, (B) sagittal ¹⁸F-PSMA-1007 PET, and (C) sagittal fused images revealed multiple metastatic disease in the spine with sclerotic changes. One lesion in the upper spine showed additional intense uptake. The other sclerotic lesions in the middle spine had only very low uptake (arrows), which is due to previous external beam radiation therapy from Th9-L2. CT = computed tomography; PET = positron emission tomography; PSMA-RADS = Prostate-specific Membrane Antigen Reporting and Data System.