Multi-phasic 68Ga-PSMA PET/CT in detection of early recurrence in prostate cancer patients with PSA < 1 ng/ml: a prospective study of 135 cases.

Purpose: The main objective of this prospective study was to determine the impact of multi-phasic acquisition of 68Ga-PSMA PET/CT in the detection of recurrent prostate cancer (PCa) in the early stage of biochemical recurrence (BR) with prostate-serum-antigen (PSA) level <1ng/ml. Also, 68Ga-PSMA PET/CT positivity was correlated with clinical parameters for the assessment of predictive markers. Methods: A prospective monocentric study was conducted on 135 PCa patients with BR and PSA<1ng/ml. All patients have undergone initial prostatectomy with additional radiation therapy in 19.3% and androgen-deprivation therapy (ADT) in 7.4% of patients. Dynamic acquisition [1-8min. post-injection (p.i.)] from the prostate bed, standard whole-body (60min. p.i.) and limited bed positions of delayed studies (120-150min. p.i.), were performed. Studies were reviewed by two board-certified nuclear medicine specialists, independently. A combination of visual and semi-quantitative analyses and correlation with morphological (e.g. MRI) and/or clinical follow-up findings was used for the final interpretation of abnormal lesions as benign or malignant. 68Ga-PSMA PET/CT positivity was also correlated with primary clinical findings. Results: Incorporating the information of all phases, 116 lesions were detected in 49.6% of patients (22 local recurrences, 63 lymph nodes, and 31 distant metastases). The detection rates were 31.8%, 44.9%, and 71.4% for PSA<0.2ng/ml, 0.2≤PSA<0.5, and 0.5≤PSA<1, respectively. Additional dynamic and/or delayed phases resulted in better determination of equivocal lesions and a higher diagnostic performance in 25.9% of patients. Stand-alone dynamic and delayed images led to better interpretation of equivocal findings in the prostate bed (31.4%) and other (lymph node/bone) lesions (20%), respectively. Conclusion:68Ga-PSMA PET/CT revealed promising results for the early detection of recurrent disease in patients with PSA level of 0.5-1.0ng/ml. However, it showed limited value in cases with PSA<0.5ng/ml. Multi-phasic 68Ga-PSMA PET/CT led to better determination of equivocal findings. Although, dynamic images may provide helpful information in assessment of the prostate bed; however, delayed acquisitions seem to have higher impact in clarifying of the equivocal findings.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2020 Feb 14 [Epub ahead of print]

Mohsen Beheshti, Reyhaneh Manafi-Farid, Hans Geinitz, Reza Vali, Wolfgang Loidl, Felix M Mottaghy, Werner Langsteger

Department of Nuclear Medicine, University Hospital, RWTH University, Aachen, Germany, Germany., Research Center for Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences, Iran, Islamic Republic of., Department of Radiation Oncology, Ordensklinikum, St. Vincent's Hospital, Austria., Department of Diagnostic Imaging, The Hospital for Sick Children, University of Toronto,, Canada., Department of Urology, Prostate Cancer Center, Ordensklinikum, Austria., Dept of Nuclear Medicine & Endocrinology, PET - CTCenter LINZ, Ordensklinikum, St Vincent's Hospital.