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PD17-07 DETECTION RATE OF 68GA-PSMA-11 PET/MRI IN PATIENTS WITH RECURRENT PROSTATE CANCER FOLLOWING RADICAL PROSTATECTOMY AND LOW PSA VALUES ⩽ 0.5 NG/ML

INTRODUCTION AND OBJECTIVES: Simultaneous 68Ga-PSMA-11 PET/MRI showed some improvement in the detection of recurrent prostate cancer at low serum prostate specific antigen (PSA) levels between 0.2 - 0.5 ng/ml compared to the already high detection rate of 68Ga-PSMA-11 PET/CT. Our group therefore analyzed all patients with early biochemical recurrence (EBR) and PSA values ⩽ 0.5 ng/ml to assess the detection rate for 68Ga-PSMA-11 PET/MRI and its effect on salvage radiotherapy. METHODS: We retrospectively analyzed a cohort of 66 consecutive patients who underwent a 68Ga-PSMA-11 PET/MRI for EBR with a PSA value ⩽ 0.5 ng/ml in our institution. Median PSA level was 0.23 ng/ml (interquartile range: 0.22 ng/ml). Detection of PSMA-positive lesions within the prostate fossa, local and distant lymph nodes, bones or visceral organs was recorded. All scans with 68Ga-PSMA-11 PET/MRI positive lesions were assessed by a radiation oncologist, to judge if the radiotherapy plan would be adjusted according to the 68Ga-PSMA-11 PET/MRI results. RESULTS: Overall, in 36 of 66 patients (54.5%) PSMA-positive lesions were detected; in 26 of 40 (65%) patients with a PSA between 0.2 - 0.5 ng/ml and in 10 of 26 (38.5%) patients with a PSA < 0.2 ng/ml. Overall 4 of the 66 patients were scanned with rising PSA levels after previous ADT. In all of those patients, PSMA positive lesions were detected. Even at those low PSA values, only 8 of 66 (12.1%) of patients had local recurrence only. In 23 patients lymph nodes and in 5 patients bone metastases were detected on 68Ga-PSMA-11 PET/MRI. The radiotherapy plan would have been changed according to the disease distribution in 25 of 66 patients (37.8%). CONCLUSIONS: Our data confirm that 68Ga-PSMA-11 PET/MRI has a high detection rate for recurrent prostate cancer, even at low PSA levels ⩽ 0.5 ng/ml and shows that even at very low PSA values the radiotherapy would have been adapted based on the 68Ga-PSMA-11 PET/MRI results in nearly 40% of the patients. Source of Funding: none