Dr Ravi on Quantitative Results From PSMAtrack in mHSPC

Praful Ravi, MB, BChir, MRCP, the medical director of GU Theranostics and a physician at Dana-Farber Cancer Institute as well as an assistant professor of medicine at Harvard Medical School, discussed quantitative findings from the phase 4 PSMAtrack study (NCT06479187) of changes in PSMA-PET during initial therapy in patients with metastatic hormone-sensitive prostate cancer.

The rationale for this study stemmed from the well-established observation that prostate-specific antigen (PSA) levels measured 6 months after treatment are highly prognostic for long-term outcomes in patients with prostate cancer, Ravi began. This association has been consistently demonstrated across multiple clinical trials evaluating both doublet and triplet treatment regimens, including analyses from the STAMPEDE platform, he noted. Building on these findings, investigators sought to determine whether PSMA-PET performed at the 6-month time point could provide additional insight into residual disease burden and prognosis, he said.

The study revealed that all 20 patients had residual PSMA-avid disease on 6-month PET imaging, indicating persistent radiotracer uptake despite systemic therapy, Ravi explained. Defined as uptake greater than the blood pool, 100% of patients demonstrated residual PSMA-avid lesions. Even when a more stringent criterion of uptake greater than the liver was applied—a threshold commonly used in studies of castration-resistant prostate cancer—85% of patients remained PSMA-positive.

Investigators then stratified patients according to six-month PSA levels, using a cutoff of 0.2 ng/mL, which has previously been associated with long-term clinical outcomes, Ravi said. Differences were observed in maximum standardized uptake value (SUVmax), he reported. Patients with lower PSA levels had a median SUVmax of 8.7 ng/mL whereas those with PSA levels above 0.2 ng/mL had a markedly higher median SUVmax of 47.4 ng/mL, he noted.

Because higher SUVmax has been associated with disease burden and outcomes following PSMA-targeted radiopharmaceutical therapy, these findings suggest that combining PSA measurements with PSMA PET imaging may provide valuable prognostic information, Ravi said. Together, the results highlight the potential role of 6-month PSMA PET as a biomarker for assessing treatment response and identifying patients at higher risk for adverse outcomes, he concluded.