Delayed PSMA PET/CT Imaging for Diagnosing Clinically Significant Prostate Cancer in Biopsy-Naïve Men With Suspected Prostate Cancer

Condition(s) studied

Investigational drug(s) / intervention(s)

[⁶⁸Ga]Ga-PSMA PET/CT with Delayed Pelvic PET-Only Acquisition: All enrolled patients undergo a dual-phase PSMA PET/CT imaging protocol consisting of: (1) a standard whole-body PET/CT acquisition performed at approximately 60 minutes after intravenous administration of \[⁶⁸Ga\]Ga-PSMA-11; and (2) a delayed pelvic PET acquisition performed at approximately 2-3 hours post-injection (exact timing to be standardized across participating centers based on local protocols and clinical workflow). The delayed phase does not include a separate CT scan; images are reconstructed using the CT dataset obtained from the initial whole-body acquisition for attenuation correction.

Study summary

Brief Summary This prospective, multicenter study evaluates whether delayed PSMA PET imaging improves diagnostic efficacy for detecting clinically significant prostate cancer (Gleason score ≥7) compared with standard imaging in patients with suspected newly diagnosed prostate cancer. Each patient serves as their own control, with diagnostic performance compared between standard (60-minute) and delayed (2-3 hour) acquisitions.

Background PSMA PET has transformed prostate cancer imaging, with emerging evidence suggesting delayed acquisition may further improve diagnostic accuracy by increasing tumor-to-background ratio. Recent studies demonstrate that delayed imaging significantly reduces equivocal findings and enhances detection of clinically significant prostate cancer.

Need While standard PSMA PET is well-validated, prospective multicenter data specifically evaluating the incremental diagnostic value of delayed imaging for clinically significant prostate cancer in treatment-naïve patients are lacking. This study addresses this gap by systematically comparing standard and delayed imaging in a large, well-defined cohort.

Primary Outcome The primary outcome is to compare the area under the curve (AUC) of delayed SUVmax versus standard SUVmax for detecting clinically significant prostate cancer (csPCa), and to determine whether delayed imaging is superior to standard imaging.

Secondary Outcomes

1. Optimal diagnostic thresholds for delayed imaging

1. Determine the optimal threshold for delayed SUVmax using ROC analysis with the Youden index;
2. Determine the optimal threshold for ΔSUVmax (delayed minus standard SUVmax);
3. Validate the sensitivity, specificity, and AUC of these thresholds in an independent validation set.
2. Biopsy avoidance potential In patients with PI RADS 4-5 lesions, calculate the negative predictive value (NPV) using a predefined high threshold to estimate the proportion who could safely avoid biopsy.
3. Diagnostic performance in key subgroups Compare the AUC of delayed SUVmax versus standard SUVmax for csPCa detection in patients with PI RADS 2-3 and in those with PI RADS 4-5.
4. Additional lesion detection Proportion of patients with additional csPCa lesions detected only on delayed imaging, and the proportion whose PI RADS category would be upgraded based on these findings.
5. Clinical decision impact Proportion of patients in whom management recommendations would change after incorporating delayed imaging results, compared with standard imaging alone.
6. Exploratory subgroup analyses Stratify by PSA level (\<4, 4 10, \>10 ng/mL) and PSA density (\<0.10, 0.10-0.20, \>0.20 ng/mL/cc) to identify subgroups that derive the greatest benefit from delayed imaging; additionally, explore combined subgroups such as PI RADS 3 with PSA 4-10 or PSAD 0.10-0.20.

Inclusion Criteria

1. Suspected prostate cancer based on elevated PSA (≥4.0 ng/mL) or clinical symptoms
2. Undergo PSMA PET (standard + delayed) prior to prostate biopsy
3. Willing to undergo prostate biopsy
4. Provide written informed consent Exclusion Criteria

1\. Prior prostate cancer treatment before PSMA PET imaging 2. Other malignancy within past two years 3. Investigator-judged risk of serious complications interfering with study conduct

Eligibility

Primary outcome measure(s)

• Area Under the Curve (AUC) of Delayed SUVmax vs. Standard SUVmax for csPCa — [Time Frame: Baseline (comparison of standard vs. delayed images)]
  Compare the AUC of delayed SUVmax versus standard SUVmax for detecting clinically significant prostate cancer (ISUP grade group ≥2) using the DeLong test , to determine whether delayed imaging is superior.

Trial sites (9)

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