68Ga-PSMA PET/CT Uptake in the Ureter Caused by Ligand Expression in Urothelial Cancer

Head-to-head comparisons of 68Ga-PSMA-11 and 18F-FDG PET/CT in evaluating patients with upper tract urothelial carcinoma: a prospective pilot study

PURPOSE

To prospectively compare the uptake of 68Ga-prostate specific membrane antigen (68Ga-PSMA)-11 and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in upper tract urothelial carcinoma (UTUC) and investigate the correlation between radiological parameters and pathological features of UTUC.

METHODS

Clinicopathologic and imaging data were collected from 10 UTUC patients who underwent preoperative 68Ga-PSMA-11 and 18F-FDG PET/CT scans. The diagnostic capabilities of both imaging techniques were analyzed and compared in UTUC. Angiogenesis in the malignancies was assessed using Chalkley counting and the expression of folate hydrolase 1 (FOLH1) and glucose transporter 1 (GLUT1) in UTUC were evaluated in the surgical specimens. Double immunofluorescence staining of PSMA and CD34 was used to examine tumor neovascularization. Tracer uptake and expression were compared and explored. Additionally, 10 patients with clear cell renal cell carcinoma (ccRCC) were included for prospective, comparative research.

RESULTS

Ten UTUC patients with 12 malignant lesions and another 10 ccRCC patients were included. 18F-FDG PET/CT demonstrated a more effective detection of UTUC foci compared to 68Ga-PSMA-11 PET/CT (the SUVmax of 18.48 ± 6.73 vs. 4.38 ± 1.45, P < 0.01). Immunohistochemical analysis revealed a statistically significant difference in the expression of PSMA and GLUT1 in UTUC (P = 0.048), with higher pathological grades showing more intense GLUT1 staining than PSMA (75% vs. 12.5%). The Chalkley counting of angiogenesis in ccRCC was significantly higher than that in UTUC (229.34 vs. 71.67), which was proportional to 68Ga-PSMA-11 PET/CT SUVmax (both P < 0.05).

CONCLUSION

18F-FDG PET/CT holds better clinical potential for evaluating UTUC and detecting lymph node metastasis compared to 68Ga-PSMA-11 PET/CT, likely due to the relatively scant expression of FOLH1 in tumor neovascular endothelium while the abundant expression of GLUT1 in malignancy. Furthermore, the lower neovascular density in UTUC should not be overlooked.

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.

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.

Prostate-Specific Membrane Antigen-Avid Bone Metastases From Urothelial Carcinoma of the Bladder

ABSTRACT

Prostate-specific membrane antigen (PSMA) PET findings of urothelial carcinoma were rarely reported. We describe 18 F-FDG PET/CT and 68 Ga-PSMA-11 PET/MRI findings in a case of urothelial carcinoma of the bladder with bone metastases in the sternum, ribs, spine, pelvis, and femurs. The bone metastases showed isodensity to hyperdensity and mild to intense FDG uptake on FDG PET/CT and moderate to intense PSMA uptake on PSMA PET/MRI. PSMA PET/MRI more clearly delineated the bone metastases compared with FDG PET/CT.

Urothelial Carcinoma and Prostate-specific Membrane Antigen: Cellular, Imaging, and Prognostic Implications

CONTEXT

Staging, restaging, and surveillance of urothelial carcinoma (UC) is challenging due to suboptimal accuracy of standard of care imaging modalities. Prostate-specific membrane antigen (PSMA) imaging may serve to improve characterisation of UC.

OBJECTIVE

To appraise available literature regarding cellular, imaging, and prognostic implications of PSMA for UC.

EVIDENCE ACQUISITION

A systematic review was performed considering all available literature (including conference abstracts) published from 1990 to 2020 and reported according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines following registration in PROSPERO (CRD42020186744). All relevant texts relating to immunohistochemical analysis and PSMA-based imaging in UC were included and collated. Additionally, FOLH1 (gene encoding PSMA) expression according to The Cancer Genome Atlas (TCGA) database was analysed as well as according to consensus and TCGA molecular classification subtypes and subsequently compared with clinical outcomes.

EVIDENCE SYNTHESIS

PSMA expression across UC tumour tissue was heterogeneous (0-100%) but appeared to decrease with increased grade and stage. The TCGA analysis demonstrated loss of FOLH1 expression with increasing T stage (p = 0.0180) and N stage (p = 0.0269), and reduced FOLH1 expression was associated with worse disease-free survival. PSMA expression in UC neovasculature was variable but mostly increased (44-100%). Eleven reports of PSMA-based imaging for UC were identified, reporting on 18 patients. PSMA positron emission tomography (PET) imaging was positive in 17 out of 18 patients. The included literature review data were limited by mostly low-quality, retrospective studies.

CONCLUSIONS

Tissue PSMA, or FOLH1 expression, may inversely be associated with pathological and survival outcomes in localised UC. PSMA PET imaging may improve detection of metastatic disease and response to systemic therapy due to PSMA expression in neovasculature. Available evidence is limited; thus, larger, prospective studies are required to confirm early results and define populations that benefit most.

PATIENT SUMMARY

In this systematic review, we assess the potential role of prostate-specific membrane antigen in urothelial cancer. We found that its utility is in expression of blood vessels surrounding metastasis. We conclude that it may be beneficial in detecting metastasis and response to systemic therapies.

Comparison of Dual-Tracer PET and CT Features to Conventional Risk Categories in Assessing Response to 177Lu-PSMA-617 Therapy for Metastatic Prostate Adenocarcinoma with Urinary Bladder Involvement

The present communication details the imaging characteristics, peculiarities, and response to ¹⁷⁷Lu-labeled prostate-specific membrane antigen (PSMA)-617-targeted radioligand therapy (PRLT) in accordance with Gleason score and use of dual-tracer PET (⁶⁸Ga-PSMA-11 and ¹⁸F-FDG) in patients with urinary bladder invasion or metastasis by prostate cancer, including the prognostic value of ¹⁸F-FDG PET in predicting response to treatment. The CT attenuation units (Hounsfield units) correlated with the prostate primary in the case of direct tumor extension from the prostate, whereas in hematogenous metastatic seeding the Hounsfield units were lower than in the primary prostatic tumor. A favorable outcome to ¹⁷⁷Lu-PSMA-617 PRLT was observed in patients with low or no baseline ¹⁸F-FDG uptake despite a high Gleason score and a high-risk National Comprehensive Cancer Network prognostic category and did not correlate with the latter alone, whereas a high SUV_max on ¹⁸F-FDG PET/CT was associated with an adverse outcome. These findings suggest a promising role for ¹⁸F-FDG PET/CT in predicting therapeutic outcomes more confidently, and hence the concept of dual-tracer PET appears to hold good in prostate adenocarcinoma theranostics.