(UroToday.com) The 2025 ASCO annual meeting featured a prostate cancer session and a presentation by Dr. Louise Emmett discussing ‘one button push’ fully automated PSMA PET quantification and the correlation with progression free and overall survival in patients undergoing 177Lu PSMA therapy for metastatic castrate resistant prostate cancer (mCRPC). 177Lu PSMA is an effective treatment in mCRPC. Whole body standardized uptake value (SUV)mean and total tumor volume are valuable screening biomarkers for 177Lu-PSMA therapy, but require labor intensive semi-quantitative software. This study, presented at the ASCO 2025 annual meeting, aimed to compare PSMA SUVmean and total tumor volume from fully automated and semi-automated methods of PSMA-PET quantification for predictive and prognostic capability.
Datasets of participants from ethics approved trials with mCRPC post androgen receptor signaling inhibition and post taxane (or unfit for taxane), treated with 177Lu PSMA, with a prior screening 68Ga-PSMA-11 PET/CT, and outcome data including PSA progression-free survival and overall survival were included. Screening 68Ga-PSMA-11 PET/CT of participants was quantified using MIM LesionID Pro to derive SUVmean and total tumor volume with a fully automated quantification process (Method A) and semi-automated quantification adjusted manually for error (Method B):
Both methods utilized software that segmented all lesions above SUVmax 3 and a CT-based deep learning method to identify normal organs for automatic physiological uptake removal. SUVmean and total tumor volume were evaluated in quartiles. Associations between SUVmean and total tumor volume above and below the 75th percentile (Q4 versus Q1-3) were examined with Kaplan Meier estimates and log-rank tests.
Data from 139 participants were analyzed, with a median age of 69 years (IQR: 64–74) and a median PSA of 94 ng/ml (IQR: 34–325):
The median time to PSA progression-free survival (120 events) was 5.5 months (95% CI 4–6.0), and overall survival (82 events) was 13.5 months (95% CI 11– 18). With method A (fully automated), SUVmean Q4 was 9.7, and total tumor volume Q4 was 1,156 ml. The corresponding results with method B (manually adjusted) were SUVmean Q4 9.9 and total tumor volume Q4 1,203 ml.
With method A, median PSA progression-free survival for SUVmean Q1-3 was 4.5 (95% CI 3–6) versus 7 months (95% CI 5–11) for SUVmean Q4 (p = 0.003). Median overall survival for SUVmean Q1-3 was 13.0 (95% CI 10–17) versus 20 months (95% CI 11.0–NE) for SUVmean Q4 (p = 0.011).
For total tumor volume Q4 versus Q1-3, median overall survival was 8.5 (95% CI 7 –12.0) versus 18 months (95% CI 13–20) (p < 0.001). With method B, median PSA progression-free survival for SUVmean Q1-3 was 4.5 (95% CI 3– 6) versus 7.5 months (95% CI 5–11) for SUVmean Q4 (p = 0.002). Median overall survival for SUVmean Q1-3 was 13 (95% CI 10–17) versus 20 months (95% CI 11 – NE) for SUVmean Q4 (p = 0.03). For total tumor volume Q4 versus Q1-3, median overall survival was 8.5 (95% CI 7–12) versus 18 months (95% CI 13 – 20) (p < 0.001).
Dr. Emmett concluded her presentation discussing ‘one button push’ fully automated PSMA PET quantification and the correlation with progression free and overall survival in patients undergoing 177Lu PSMA therapy for mCRPC with the following take home points:
- PSMA SUVmean and total tumor volume with a fully automated quantification method predicted both PSA progression-free survival and overall survival in patients undergoing 177Lu PSMA therapy
- This is an important step in moving PSMA-PET quantitative biomarkers from research tool to routine clinical care
Presented by: Louise Emmett, MBChB, FRACP, FAANMS, MD, St Vincent's Hospital, Sydney, Australia
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the American Society of Clinical Oncology (ASCO) 2025 Annual Meeting, Chicago, IL, Fri, May 30 – Tues, Jun 3, 2025.
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