(UroToday.com) The 2025 SNMMI annual meeting featured a clinical diagnosis and therapy session and a presentation by Dr. Kambiz Rahbar discussing the clinical value of the PROSTest to detect biochemical recurrence in prostate cancer. Nearly 1/3 of patients with prostate cancer experience biochemical recurrence after primary definitive therapy. Biochemical recurrence (detectable PSA levels >0.1 ng/mL) are associated with an increased risk of metastasis and mortality in patients with prognostically unfavorable features. PSMA-PET/CT has been successfully used for tumor identification and therapy planning in biochemical recurrence. However, its efficacy in confirming biochemical recurrence, especially at lower PSA levels, is limited.
The PROSTest is a novel blood-based 27-gene mRNA expression assay followed by a machine learning algorithm that produces a score on a scale of 0-100. The score is translated into a binary readout (positive or negative) based on a clinically validated cutoff of 50, and has shown diagnostic and prognostic values in prostate cancer. This study, presented at SNMMI 2025, evaluated the utility of the PROSTest for detecting biochemical recurrence compared to imaging.
There were 186 men with a median age of 72 years (range: 48-84) who were recruited from three Nuclear Medicine centers (Basel, Switzerland; Münster, Germany; Warsaw, Poland) for PSMA-PET/CT imaging following a diagnosis of biochemical recurrence. Blood samples were collected in Wren’s proprietary tubes at the time of PSMA-PET/CT imaging. PROSTest was measured, and results were compared to imaging results using McNemar’s and Chi square -testing.
The median PSA level was 0.87 ng/mL (range: 0.1-38 ng/mL), with 41 patients (22%) having a PSA of 0.1 - 0.5 ng/mL. PSMA-PET/CT showed findings compatible with recurrent prostate cancer in 147/186 (78%) of patients, including in 27 of the 44 (61%) patients with low PSA levels:
PROSTest was positive (scores > 50%) in 175/186 (94%) of patients, with a median PROSTest score of 78 (range: 12-100). PROSTest was positive in 38/39 (99.5%) of patients with negative PSMA-PET/CT (McNemar’s test: p = 0.0006), and in 41/44 (93%) patients with low PSA levels:
The PROSTest was significantly better than imaging (61%: 27/44, Chi squared = 12.53, p = 0.0004) for confirming recurrent disease in patients with low PSA levels.
Dr. Rahbar concluded his presentation discussing the clinical value of the PROSTest to detect biochemical recurrence in prostate cancer with the following take home points:
- PROSTest appears superior to PSMA-PET/CT imaging for detecting recurrent prostate cancer, particularly at low (<0.5 ng/mL PSA levels)
- Based on the extremely high positivity rate (99.5%), PROSTest could be used as a confirmatory tool for biochemical recurrence in patients with negative imaging
- Moreover, clinical integration of PROSTest score with imaging may have utility for identifying prostate cancer patients with poorer prognostic features
Presented by: Kambiz Rahbar, MD, University Hospital Münster, Münster, Germany
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2025 Annual Meeting, New Orleans, LA, Sat, Jun 21 – Tues, Jun 24, 2025.