Mohsen Beheshti1,2,3, Reyhaneh Manafi-Farid4, Hans Geinitz5, Reza Vali6, Wolfgang Loidl7, Felix M Mottaghy8,9, Werner Langsteger3. 1. Department of Nuclear Medicine, University Hospital, RWTH University, Aachen, Germany mbeheshti@ukaachen.de. 2. Department of Nuclear Medicine, Paracelsus Medical University, Salzburg, Austria. 3. Department of Nuclear Medicine and Endocrinology, PET-CT Center Linz, St. Vincent's Hospital, Linz, Austria. 4. Research Center for Nuclear Medicine, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran. 5. Department of Radiation-Oncology, St. Vincent's Hospital, Linz, Austria. 6. Department of Diagnostic Imaging, Hospital for Sick Children, University of Toronto, Toronto, Canada. 7. Department of Urology, St. Vincent's Hospital, Linz, Austria; and. 8. Department of Nuclear Medicine, University Hospital, RWTH University, Aachen, Germany. 9. Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, Netherlands.
Abstract
The main objective of this prospective study was to determine the impact of multiphasic acquisition of 68Ga-PSMA PET/CT in the detection of recurrent prostate cancer in the early stage of biochemical recurrence with a prostate-specific antigen (PSA) level of less than 1 ng/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 prostate cancer patients with biochemical recurrence and a PSA level of less than 1 ng/mL. All patients had undergone initial prostatectomy, with additional radiation therapy in 19.3% of patients and androgen-deprivation therapy in 7.4%. The patients underwent dynamic acquisitions from the prostate bed (1-8 min after injection), standard whole-body acquisitions (60 min after injection), and limited-bed-position delayed acquisitions (120-150 min after injection). The studies were reviewed by 2 board-certified nuclear medicine specialists, independently. A combination of visual and semiquantitative analyses and correlation with morphologic (e.g., MRI) or clinical follow-up findings was used for the final interpretation of lesions as benign or malignant. 68Ga-prostate-specific membrane antigen (PSMA) PET/CT positivity was also correlated with primary clinical findings. Results: Incorporating the information from all phases, we were able to detect 116 lesions 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 < 0.2 ng/mL, 0.2 ≤ PSA < 0.5, and 0.5 ≤ PSA < 1, respectively. Additional dynamic 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 in other lesions (lymph node or bone) (20%), respectively. Conclusion: 68Ga-PSMA PET/CT showed promise for early detection of recurrent disease in patients with a PSA level of 0.5-1.0 ng/mL. However, it showed limited value in patients with a PSA level of less than 0.5 ng/mL. Multiphasic 68Ga-PSMA PET/CT led to a better determination of equivocal findings. Although dynamic images may provide helpful information for assessment of the prostate bed, delayed acquisitions seem to have a greater impact in clarifying equivocal findings.
The main objective of this prospective study was to determine the impact of multiphasic acquisition of 68Ga-PSMA PET/CT in the detection of recurrent prostate cancer in the early stage of biochemical recurrence with a prostate-specific antigen (PSA) level of less than 1 ng/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 prostate cancerpatients with biochemical recurrence and a PSA level of less than 1 ng/mL. All patients had undergone initial prostatectomy, with additional radiation therapy in 19.3% of patients and androgen-deprivation therapy in 7.4%. The patients underwent dynamic acquisitions from the prostate bed (1-8 min after injection), standard whole-body acquisitions (60 min after injection), and limited-bed-position delayed acquisitions (120-150 min after injection). The studies were reviewed by 2 board-certified nuclear medicine specialists, independently. A combination of visual and semiquantitative analyses and correlation with morphologic (e.g., MRI) or clinical follow-up findings was used for the final interpretation of lesions as benign or malignant. 68Ga-prostate-specific membrane antigen (PSMA) PET/CT positivity was also correlated with primary clinical findings. Results: Incorporating the information from all phases, we were able to detect 116 lesions 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 < 0.2 ng/mL, 0.2 ≤ PSA < 0.5, and 0.5 ≤ PSA < 1, respectively. Additional dynamic 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 in other lesions (lymph node or bone) (20%), respectively. Conclusion: 68Ga-PSMA PET/CT showed promise for early detection of recurrent disease in patients with a PSA level of 0.5-1.0 ng/mL. However, it showed limited value in patients with a PSA level of less than 0.5 ng/mL. Multiphasic 68Ga-PSMA PET/CT led to a better determination of equivocal findings. Although dynamic images may provide helpful information for assessment of the prostate bed, delayed acquisitions seem to have a greater impact in clarifying equivocal findings.