Prostate-specific membrane antigen (PSMA) PET/CT imaging demonstrates the ability to detect prostate cancer recurrence in patients before they meet the Phoenix criteria for biochemical recurrence, defined as a PSA rise of 2.0 ng/mL or more above the PSA nadir following curative treatment. The findings, published in European Urology Oncology, suggest earlier detection can lead to improved treatment options and outcomes.
The retrospective analysis included 568 patients, with 222 (39.1%) not meeting the Phoenix criteria (Ph-) and 346 (60.9%) meeting the criteria (Ph+). Patients underwent PSMA PET/CT scans using various PSMA PET/CT tracers. The median PSA rise was 1.09 ng/mL in the Ph- cohort and 3.63 ng/mL in the Ph+ cohort. Baseline characteristics were similar between the two groups.
Detection Rates and Disease Stage
PSMA-avid lesions were detected in 170 patients (76.6%) in the Ph- group and 322 patients (93.1%) in the Ph+ group. A significant portion of the Ph- cohort (46.5%) presented with local recurrence alone, compared to 32.3% of the Ph+ cohort (OR 1.82; P = .002). Distant metastases were detected in 21.8% of Ph- patients versus 48.8% of Ph+ patients (OR, 0.29; P < .001). Oligometastatic disease was present in 42.9% of Ph- patients and 28.9% of Ph+ patients (OR, 1.85; P = .002).
Treatment Suitability and Outcomes
Of those with PSMA-avid lesions, 75.9% of Ph- patients were potentially suitable for local salvage therapy, compared with 45% of Ph+ patients (odds ratio [OR], 3.84; P < .001). Overall, 90% of patients in the Ph- cohort were eligible for either salvage treatment or metastasis-directed therapy (MDT), compared with 61.8% in the Ph+ cohort (OR, 5.56; P < .001).
According to lead author Evelien J E van Altena, “The majority (76%) of patients not yet meeting the Phoenix criteria did have PSMA-avid lesions on PSMA-PET, suggesting [prostate cancer] recurrence. Early PSMA-PET in these patients detected recurrences at a significantly less advanced disease stage, allowing potential salvage and MDT options.”
Impact on Disease Progression and Survival
Patients in the Ph- cohort experienced a longer time to the initiation of androgen deprivation therapy (ADT) and progression to castration-resistant prostate cancer (CRPC) compared with patients in the Ph+ cohort (both P < .001). The Ph- arm also demonstrated improved overall survival (P < .001), with a 5-year mortality rate of 5.9% (n = 13) versus 15.2% (n = 50) in the Ph+ cohort (OR, 0.30; 95% CI, 0.15-0.60; P < .001).
Predictive Value and Limitations
Additional data showed that the positive predictive value of PSMA PET/CT was 80.3% for local recurrences and 93.6% for metastatic disease. The authors acknowledge that the retrospective nature of the study introduces the potential for lead-time bias.
van Altena concluded, “Early PSMA-PET in our study was associated with a delay of ADT, CRPC onset, and overall-mortality. However, prospective studies are warranted to validate these results.”
