PSMA PET/CT is efficacious in detecting renal cancer metastases

Data from a recent study published in European Urology Focus showed that prostate-specific membrane antigen (PSMA) PET/CT detected more metastatic lesions than conventional imaging at primary staging for renal cancer.¹

PSMA PET scans resulted in a change of management in 32% of patients included in the study.

Overall, PSMA PET scans identified 195 presumed metastatic lesions, compared with 160 with conventional imaging. PSMA PET/CT was also shown to identify more distant lymph nodes (24 vs 10), bone lesions (38 vs 19), other distant lesions (27 vs 12), and vena cava tumor propagation (8 vs 5) compared with conventional imaging.

However, conventional imaging identified more primary tumors (64 vs 59) and pulmonary lesions (69 vs 53) compared with PSMA PET/CT. The 2 modalities were similar in their detection of regional lymph nodes (49 vs 44).

“High PSMA expression allows PSMA PET imaging to identify presumed metastatic lesions that are occult on conventional imaging, which are largely size-dependent according to Response Evaluation Criteria in Solid Tumours,” wrote the authors.¹

The investigators also found that PSMA PET scans resulted in a change of management in 32% of patients, of which 20% (n = 13) were major changes and 12% (n = 8) were minor.

Of those patients with a major change in management, 9 received surgery, 2 received systemic therapy, and 2 were placed on watchful waiting. Among those with a minor change in management, scans resulted in a change of surgical approach for 5 patients and the addition of a further treatment modality in 3 patients.

Patients who underwent a treatment modification based on PSMA PET/CT had a median progression-free survival (PFS) of 19.7 months (IQR, 17-25). Those who underwent surgery after findings on PSMA PET/CT had a median PFS of 24 months (IQR, 18-36).

Overall, the study was conducted via a retrospective review of PSMA PET/CT scans for primary staging of renal cancer across 3 sites in Brisbane, Australia. In total, 61 scans were included, of which 52 were for primary staging of a suspected renal tumor and 9 were included following incidental renal tumor detection during staging of synchronous prostate cancer.

In total, 74% of those included in the study were male. The median age was 65 years. Median follow-up was 13.3 months.

Clinicopathologic and management differences between PSMA PET/CT and conventional imaging were compared. PSMA PET/CT was conducted within 6 weeks of initial conventional imaging.

Histopathology of the primary tumor was available for 51 patients included in the study. Most renal cancers were PSMA-avid regardless of histological subtype. Clear cell renal cell carcinoma (ccRCC) tumors more frequently had PSMA avidity compared with non-ccRCC tumors (97.5% vs 75%), but the difference did not reach statistical significance (P = .32). SUVmax was also shown to be higher for ccRCC tumors than for non-ccRCC tumors upon comparison of histological subtypes (11.0 vs 3.6; P = .12).

The authors concluded, “Our results show that PSMA PET detected more metastatic lesions at diagnosis and could rule out possible metastases identified on conventional imaging, resulting in a management change for one-third of the cohort. While preliminary in nature, these data provide a compelling rationale for consideration of PSMA PET as an alternative staging modality at the time of primary diagnosis.”¹

Reference

1. Tariq A, Pearce A, Rhee H, et al. The role of prostate-specific membrane antigen positron emission tomography/computed tomography in primary staging of selected renal tumours: Initial experience in a multicentre cohort. Eur Urol Focus. 2024:S2405-4569(23)00296-1. doi:10.1016/j.euf.2023.12.004