PSMA-11 PET/CT for Detection of Recurrent Prostate Cancer in Patients With Negative Choline PET/CT

The detection rate of PSMA-11 PET/CT in biochemical recurrence prostate cancer patients and negative choline PET/CT is not well known. Our study showed that PSMA-11 PET/CT is able to detect occult biochemical recur-rence even in this selected population of patients, and even at low PSA levels. A majority of patients with a positive examination initiated a treatment following PSMA-11 PET/CT. Patient management changed in 39.8%. Introduction: Prostate adenocarcinoma (CaP) is the leading cancer in men. After curative treatment, from 27% to 53% of patients will experience biochemical recurrence (BR). With the development of focal therapies, precise early identification of recurrence's sites is of utmost importance in order to deliver individualized treatment on positive lesions. The aim of this study was to assess the detection rate (DR) of 68Ga-PSMA-11 positron emission tomography/computed tomography (PET/CT) in selected patients with prostate cancer BR and recent negative 18F-choline PET/CT. Patients and Methods: We performed a retrospective analysis including all patients with CaP referred for BR with a negative 18F-choline PET/CT, and who underwent 68Ga-PSMA-11 PET/CT between October, 2018 and December, 2019. The overall DR of 68Ga-PSMA-11 PET/CT was calculated, and described according to BR characteristics especially PSA levels and velocity. Patients were followed up for at least 1 year. Patient management following 68 Ga-PSMA-11 PET/CT and PSA levels evolution after treatment were also recorded. Results: One hundred fifty-nine patients comprising 164 examinations were analyzed. The overall DR of 68Ga-PSMA-11 PET/CT for BR was 65.9% (95CI, 58.6-73.1). The DR was 52.5% (95CI, 39.9-65.0), 70.6% (95CI, 55.3-85.9), 70.4% (95CI, 53.1-87.6), and 78.6% (95CI, 66.2-91.0) for PSA levels between 0.2 and 0.49 ng/mL, 0.5 to 0.99 ng/mL, 1 to 1.99 ng/mL and PSA >= 2 ng/mL, respectively. The DR was 70.7% (95CI, 59.0-82.4) with a PSA doubling time (PSA-DT) <= 6 months and 65.2% (95CI, 55.5-74.9) with a PSA-DT > 6 months. Around 3/4 of patients (75.9%) with a positive 68Ga-PSMA-11 PET/CT initiated treatment, including surgery (2.4%), stereotactic radiotherapy +/- androgen deprivation therapy (ADT) (22%) or external conformational radiotherapy +/- ADT (46.3%). Patient management changed in 43 cases (39.8%). Conclusion: Our study confirmed the ability of 68Ga-PSMA-11 PET/CT to detect occult biochemical recurrence, even in a selected population of CaP patients with negative 18F-choline PET/CT, even at low PSA levels.