PSMA-PET/PSA Scans Identifies Residual Disease in Metastatic HPSC

Prostate-specific membrane antigen (PSMA)–PET and PSA scans following 6 months of systemic treatment may be predictive for residual disease among patients with metastatic hormone-sensitive prostate cancer (HSPC), according to findings from a quantitative analysis of the prospective PSMAtrack trial (NCT06479187) presented in a poster session at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.¹

Among 20 patients who underwent evaluation for PSMA-PET changes between baseline and 6 months in the trial protocol, the median PSA level was 0.29 ng/mL at 6 months (range, less than 0.02-177), with 55% having a PSA of 0.2 ng/mL or greater. Moreover, residual PSMA-avid disease was observed in 100% of patients in the blood pool and 85% of patients in the liver. The most common sites of residual disease included the prostate (90%), bone (80%), pelvic lymph node (55%), and non-regional lymph nodes (50%). New lesions were identified on PSMA-PET among 20% of patients.

Regarding PSMA-PET parameters, the total tumor volume (TTV) was 7.7 mL (range, 0.4-79.9) among the PSA less than 0.2 ng/mL population (n = 9) vs 147 mL (range, 5.9-344) among the PSA 0.2 ng/mL or greater group (n = 11; P <.01). Moreover, the median SUVmax was 8.7 (range, 4.8-39.2) vs 47.4 (range, 11.7-162) in each respective group (P <.01). The median SUVmean in each group was 5.3 (range, 4.0-8.8) vs 6.4 (range, 4.2-16.8; P = 0.14).

“All patients had residual PSMA-avid disease after 6 [months] of systemic therapy for [metastatic] HSPC,” Praful Ravi, MB, BChir, MRCP, assistant professor of medicine at Harvard Medical School and medical director of Genitourinary Theranostics at Dana-Farber Cancer Institute, wrote in the presentation with study coinvestigators.¹ “[There was a] significantly higher 6-month PSMA-TTV and SUVmax in patients with PSA [greater than or equal to] 0.2ng/mL at 6 months vs a PSA [of less than] 0.2ng/mL at 6 months.[Six-month] PSMA-PET and 6-month PSA may identify patients for consolidative therapy after initial systemic therapy for [metastatic] HSPC.”

Patients in the PSMAtrack protocol had de novo/metachronous metastatic disease and planned to receive androgen deprivation therapy (ADT) plus an androgen receptor pathway inhibitor (ARPI) with or without docetaxel. Those excluded from enrollment in the quantitative analysis included those who received radiotherapy to primary or metastatic sites prior to 6-month PET. Patients initially received a baseline ¹⁸F-flotufolastat PSMA-PET scan within 21 days to the start of ADT followed by another 6 months after the initiation of treatment.

The median age on the study was 72 years (range, 60-95). Those enrolled had a median baseline PSA of 55.0 ng/mL (range, 2.2-3696), and 60% had received an ADT/ARPI without docetaxel. Moreover, 65% of patients had high volume disease per CHAARTED criteria, and 90% had de novo disease.

The primary end point of the analysis was the proportion of patients with residual disease on PSMA-PET after 6 months. An exploratory end point was to compare the 6-month PET parameters with a PSA of less than 0.2 ng/mL vs 0.2 ng/mL or greater after 6 months of treatment.

The investigators initiated the prospective analysis evaluating changes in PSMA-PET between baseline and 6 months of treatment based on limited historical data examining changes in disease extent on PSMA-PET during the initial months of metastatic HSPC treatment. They noted that a PSA of less than 0.2 ng/mL following 6 months of ADT/ARPI had “excellent” prognostic value for these patients.

Reference

Ravi P, Shah H, Liu M, et al. Quantitative results from PSMAtrack: a prospective study evaluating changes in PSMA-PET during initial systemic therapy for metastatic hormone-sensitive prostate cancer (mHSPC). J Clin Oncol. 2026;44(suppl 16):5102. doi:10.1200/JCO.44.16_suppl.5102