ASCO 2021: Diagnostic Performance of Ga-68 PSMA PET/CT Imaging In Early-Relapsed Prostate Cancer: Phase 3, Prospective, Multicenter Study (IAEA-PSMA study)

In this trial, patients with prostate cancer who have undergone primary definitive treatment and with rising PSA were recruited in the study. Overall 17 centers from 15 countries (Azerbaijan, Brazil, Colombia, India, Israel, Italy, Jordan, Lebanon, Malaysia, Mexico, Pakistan, Poland, South Africa, Turkey, and Uruguay) were involved:

Key inclusion criteria were:

• Histopathology-proven prostate adenocarcinoma with previous primary treatment and clinically established biochemical recurrence
• PSA < 4 ng/mL
• PSA > 4 and < 10 ng/mL was accepted for patients with a negative MRI and bone scintigraphy

Images and data were centrally reviewed, and data were collected for PSMA site of findings, positivity rate, defined as the percentage of patients with a positive ⁶⁸Ga-PSMA PET/CT taking into account the composite standard: pathology, correlative imaging, PSA response, with at least 6 months of clinical follow-up, and impact on patient management by determining changes in the treating physician’s documented clinical plans before and after ⁶⁸Ga-PSMA PET/CT.

There were 1,198 patients enrolled and the final cohort included data from 1,004 patients, of which 77.7% were initially treated with radical prostatectomy and 22.3% treated with radiotherapy. ⁶⁸Ga-PSMA PET/CT was positive in 654/1004 patients (65.1%), and lesions were identified as: prostate/prostatic bed only in 13.7% cases, pelvic lymph nodes only in 20.5%, and with any metastatic disease in 27.0%. There was a correlation between PSMA-PET/CT positivity and Gleason score (p<0.001): detection rate was 371/613 (60.5%) in patients with Gleason 7, 130/196 (66.3%) in Gleason 8, 140/180 (77.8%) in Gleason 9 and 13/15 (86.7%) in Gleason 10. There was also significant correlation between lesion identification and PSA values (p<0.001). Detection rate was:

• 21/41 (51.2%) for PSA <0.2 ng/mL
• 84/188 (44.7%) for PSA between 0.2-0.5 ng/mL
• 124/232 (53.4%) for PSA 0.5-1.0 ng/mL
• 158/235 (67.2%) for PSA ≥1 and <2 ng/mL
• 171/206 (83.0%) for PSA ≥2 and <4 ng/mL
• 96/102 (94.1%) in PSA 4 to 10 ng/mL

Also, treatment was modified based on PSMA results in 56.8% of patients:

The ⁶⁸Ga-PSMA PET/CT positivity was consistent and not statistically different among the countries.           

Dr. Cerci concluded his presentation with the following take-home messages:

• This trial confirms PSMA-PET/CT capability in detecting local and metastatic recurrence in most prostate cancer patients in the setting of biochemical recurrence
• PSMA-PET/CT positivity correlated with Gleason score, PSA at the time of PET, PSA doubling time and radiotherapy as primary treatment
• PSMA-PET/CT results led to changes in therapeutic management in more than half of the cohort
• The study demonstrates the reliability of PSMA-PET/CT in the workup of prostate cancer patients with biochemical recurrence, and its worldwide feasibility

Co-Authors: Stefano Fanti, IAEA Prostate Working Group; St. Orsola-Malpighi Hospital, Bologna, Italy