ProstEVs Detect Risk of Recurrence in Patients With Oligometastatic Prostate Cancer

The ORIOLE trial compared the outcomes of observation with stereotactic ablative radiation therapy (SABR) for oligometastatic prostate cancer (omPC). A team of researchers from Maryland and Minnesota recently demonstrated that plasma levels of prostate cancer-derived extracellular vesicles (ProstEVs) correlate with tumor burden and predict disease progression in omPC after SABR.

Predictive tools are needed to identify patients who can benefit from SABR. Investigators used plasma samples from the ORIOLE study to conduct a blind validation study based on this new research and presented their results at the American Society for Radiation Oncology 2023 Annual Meeting.

Plasma samples were collected from 46 patients with omPC who were involved in the ORIOLE trial, randomized 2:1 for SABR versus observation. A standardized and calibrated nanoscale flow cytometry using fluorescent prostate-specific membrane antigen (PSMA) antibodies was used to measure baseline PSMA and ProstEV levels.

Median ProstEV levels were used as a cutoff baseline for low and high levels, while Kaplan-Meier curves and Cox regression models were used to determine the association between ProstEV levels and clinical outcomes (prostate-specific antigen progression-free survival [psaPFS] and radiographic distant progression-free survival [rPFS]).

No association was observed between the number of metastatic lesions and baseline levels of prostate-specific antigen or plasma ProstEVs.

The rPFS for patients treated with SABR was 29.6 months. The rPFS for patients treated with SABR who had high ProstEV levels was 11.1 months. rPFS was 36 months for those treated with SABR who had low ProstEV levels (hazard ratio [HR], 2.85; 95% CI, 1.01-7.48; P=.02).

The psaPFS for patients treated with SABR was 11.9 months, and the psaPFS for patients with high and low ProstEV levels was 5.9 months and 24.3 months, respectively (HR, 2.44; 95% CI, 1.00-5.94; P=.03).

ProstEVs can be utilized as the first blood biomarker of tumor burden to prognosticate the risk of disease recurrence in patients with omPC treated with SABR, strengthening the clinical value of ProstEVs as personalized radiation therapy.