Survey by the French Medicine Agency (ANSM) of the practice, result and impact of ⁶⁸Ga-PSMA-11 PET/CT in the biochemical recurrence of prostate cancer with non-contributive ¹⁸F-fluorocholine PET/CT: 1177 examinations

Introduction: The Heidelberg team reported in 2015 that PET/CT with PSMA-11, a ⁶⁸Ga-labeled ligand of the prostate-specific membrane antigen, can detect prostate cancer (PC) tissue. In France, it formed the rationale for prospective submissions of nominative requests (ATU) to ANSM: perform PSMA-11 PET/CT in a patient with biochemical recurrence (BCR) of PC. To comply with this procedure, ¹⁸F-fluorocholine (FCH) must be negative or equivocal or discrepant with other imaging modalities. In the ATU agreement, it was specified that the applicant must return information to ANSM about the tolerance and efficacy of this diagnostic agent in each patient. All information obtained during the first 3 years of issuing ATUs was gathered, checked and analysed by ANSM. Patients, material and methods: Between May 2016 and April 2019, 1177 such ATUs were followed by PSMA-11 PET/CT, in 6 centres. Patients’ age: mean 69.2 years (median 69.7 range 42-89). The source of PSMA-11 was Iason (Austria) for all centres; the ⁶⁸Ge/⁶⁸Ga generator was either Galliapharm or GalliAd. The manufacturers of the PET/CT machines with time-of-flight capacity were Siemens (54% of PET/CTs), Philips (26%), or GE (20%). Results: Injected activity of PSMA-11 per kg of body mass: mean 1.8 MBq / kg (median 1.9 range 0.5-3.6). CT contrast medium: none 74%, IV 19%, oral 7%. CT dose length product: mean 627 mGy.cm (609, 209-2786). Number of image acquisitions per exam: 1 = 23%, 2 = 73%, 3 = 4%. Overall positivity rate of PSMA-PET/CT was 69%, showing distant foci in 36%. Overall impact rate on diagnostic thinking was 71%. No difference in those parameters was found according to 1) whether a contrast medium was administered or not 2) the number of image acquisitions per exam. Its positivity rate and impact on diagnostic thinking varied significantly according to the PSA serum level at PET/CT and the initial curative therapy, as reported in the table. When the Gleason score was &lt7 the positivity rate was lower: 65%.Conclusion: PET/CT with PSMA-11 can detect PC tissue in case of BCR even when FCH is non-conclusive. In this large series, this was confirmed at low PSA serum level &lt1ng/mL but also in case of non-conclusive FCH at higher PSA levels &gt2. Therefore the current imaging strategy for BCR in France could be reverted in the near future: PSMA-11 as 1^st line and then FCH if PC does not overexpress PSMA.